Brace expansion
You are encouraged to solve this task according to the task description, using any language you may know.
Brace expansion is a type of parameter expansion made popular by Unix shells, where it allows users to specify multiple similar string parameters without having to type them all out. E.g. the parameter enable_{audio,video} would be interpreted as if both enable_audio and enable_video had been specified.
- Task
Write a function that can perform brace expansion on any input string, according to the following specification.
Demonstrate how it would be used, and that it passes the four test cases given below.
Specification
In the input string, balanced pairs of braces containing comma-separated substrings (details below) represent alternations that specify multiple alternatives which are to appear at that position in the output. In general, one can imagine the information conveyed by the input string as a tree of nested alternations interspersed with literal substrings, as shown in the middle part of the following diagram:
|
It{{em,alic}iz,erat}e{d,}
|
parse
―――――▶ |
|
expand
―――――▶ | Itemized
Itemize Italicized Italicize Iterated Iterate | ||||||||||||||||||
| input string | alternation tree | output (list of strings) | ||||||||||||||||||||
This tree can in turn be transformed into the intended list of output strings by, colloquially speaking, determining all the possible ways to walk through it from left to right while only descending into one branch of each alternation one comes across (see the right part of the diagram). When implementing it, one can of course combine the parsing and expansion into a single algorithm, but this specification discusses them separately for the sake of clarity.
Expansion of alternations can be more rigorously described by these rules:
|
⟶ |
|
- An alternation causes the list of alternatives that will be produced by its parent branch to be increased 𝑛-fold, each copy featuring one of the 𝑛 alternatives produced by the alternation's child branches, in turn, at that position.
- This means that multiple alternations inside the same branch are cumulative (i.e. the complete list of alternatives produced by a branch is the string-concatenating "Cartesian product" of its parts).
- All alternatives (even duplicate and empty ones) are preserved, and they are ordered like the examples demonstrate (i.e. "lexicographically" with regard to the alternations).
- The alternatives produced by the root branch constitute the final output.
Parsing the input string involves some additional complexity to deal with escaped characters and "incomplete" brace pairs:
a\\{\\\{b,c\,d} |
⟶ |
|
|||||||
{a,b{c{,{d}}e}f |
⟶ |
|
- An unescaped backslash which precedes another character, escapes that character (to force it to be treated as literal). The backslashes are passed along to the output unchanged.
-
Balanced brace pairs are identified by, conceptually, going through the string from left to right and associating each unescaped closing brace that is encountered with the nearest still unassociated unescaped opening brace to its left (if any). Furthermore, each unescaped comma is associated with the innermost brace pair that contains it (if any). With that in mind:
- Each brace pair that has at least one comma associated with it, forms an alternation (whose branches are the brace pair's contents split at its commas). The associated brace and comma characters themselves do not become part of the output.
- Brace characters from pairs without any associated comma, as well as unassociated brace and comma characters, as well as all characters that are not covered by the preceding rules, are instead treated as literals.
For every possible input string, your implementation should produce exactly the output which this specification mandates. Please comply with this even when it's inconvenient, to ensure that all implementations are comparable. However, none of the above should be interpreted as instructions (or even recommendations) for how to implement it. Try to come up with a solution that is idiomatic in your programming language. (See #Perl for a reference implementation.)
Test Cases
Input
(single string)Ouput
(list/array of strings)~/{Downloads,Pictures}/*.{jpg,gif,png}~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
It{{em,alic}iz,erat}e{d,}, please.Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
Other tasks related to string operations:
- Metrics
- Counting
- Word frequency
- Letter frequency
- Jewels and stones
- I before E except after C
- Bioinformatics/base count
- Count occurrences of a substring
- Count how many vowels and consonants occur in a string
- Remove/replace
- XXXX redacted
- Conjugate a Latin verb
- Remove vowels from a string
- String interpolation (included)
- Strip block comments
- Strip comments from a string
- Strip a set of characters from a string
- Strip whitespace from a string -- top and tail
- Strip control codes and extended characters from a string
- Anagrams/Derangements/shuffling
- Word wheel
- ABC problem
- Sattolo cycle
- Knuth shuffle
- Ordered words
- Superpermutation minimisation
- Textonyms (using a phone text pad)
- Anagrams
- Anagrams/Deranged anagrams
- Permutations/Derangements
- Find/Search/Determine
- ABC words
- Odd words
- Word ladder
- Semordnilap
- Word search
- Wordiff (game)
- String matching
- Tea cup rim text
- Alternade words
- Changeable words
- State name puzzle
- String comparison
- Unique characters
- Unique characters in each string
- Extract file extension
- Levenshtein distance
- Palindrome detection
- Common list elements
- Longest common suffix
- Longest common prefix
- Compare a list of strings
- Longest common substring
- Find common directory path
- Words from neighbour ones
- Change e letters to i in words
- Non-continuous subsequences
- Longest common subsequence
- Longest palindromic substrings
- Longest increasing subsequence
- Words containing "the" substring
- Sum of the digits of n is substring of n
- Determine if a string is numeric
- Determine if a string is collapsible
- Determine if a string is squeezable
- Determine if a string has all unique characters
- Determine if a string has all the same characters
- Longest substrings without repeating characters
- Find words which contains all the vowels
- Find words which contain the most consonants
- Find words which contains more than 3 vowels
- Find words whose first and last three letters are equal
- Find words with alternating vowels and consonants
- Formatting
- Substring
- Rep-string
- Word wrap
- String case
- Align columns
- Literals/String
- Repeat a string
- Brace expansion
- Brace expansion using ranges
- Reverse a string
- Phrase reversals
- Comma quibbling
- Special characters
- String concatenation
- Substring/Top and tail
- Commatizing numbers
- Reverse words in a string
- Suffixation of decimal numbers
- Long literals, with continuations
- Numerical and alphabetical suffixes
- Abbreviations, easy
- Abbreviations, simple
- Abbreviations, automatic
- Song lyrics/poems/Mad Libs/phrases
- Mad Libs
- Magic 8-ball
- 99 bottles of beer
- The Name Game (a song)
- The Old lady swallowed a fly
- The Twelve Days of Christmas
- Tokenize
- Text between
- Tokenize a string
- Word break problem
- Tokenize a string with escaping
- Split a character string based on change of character
- Sequences
11l
F getitem(=s, depth = 0)
V out = [‘’]
L s != ‘’
V c = String(s[0])
I depth & (c == ‘,’ | c == ‘}’)
R (out, s)
I c == ‘{’
V x = getgroup(s[1..], depth + 1)
I !x[0].empty
out = multiloop(out, x[0], (a, b) -> a‘’b)
s = x[1]
L.continue
I c == "\\" & s.len > 1
(s, c) = (s[1..], c‘’s[1])
out = out.map(a -> a‘’@c)
s = s[1..]
R (out, s)
F getgroup(=s, depth)
[String] out
V comma = 0B
L s != ‘’
V gs = getitem(s, depth)
s = gs[1]
I s == ‘’
L.break
out [+]= gs[0]
I s[0] == ‘}’
I comma
R (out, s[1..])
R (out.map(a -> ‘{’a‘}’), s[1..])
I s[0] == ‘,’
(comma, s) = (1B, s[1..])
R ([‘’] * 0, ‘’)
L(s) |‘~/{Downloads,Pictures}/*.{jpg,gif,png}
It{{em,alic}iz,erat}e{d,}, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}’.split("\n")
print(([s] [+] getitem(s)[0]).join("\n\t")"\n")- Output:
~/{Downloads,Pictures}/*.{jpg,gif,png}
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
...
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
Ada
pragma Ada_2022;
with Ada.Containers; use Ada.Containers;
with Ada.Containers.Vectors;
with Ada.Strings.Unbounded; use Ada.Strings.Unbounded;
with Ada.Text_IO; use Ada.Text_IO;
procedure Brace_Expansion is
procedure Expand_Braces (Str : Unbounded_String) is
package Position_Vectors is new Ada.Containers.Vectors (Natural, Natural);
Escaped : Boolean := False;
Depth : Integer := 0;
Brace_Points : Position_Vectors.Vector;
Braces_To_Parse : Position_Vectors.Vector;
Prefix, Suffix, Option : Unbounded_String := Null_Unbounded_String;
begin
for Idx in 1 .. Length (Str) loop
case Element (Str, Idx) is
when '\' => Escaped := not Escaped;
when '{' =>
Depth := Depth + 1;
if not Escaped and then Depth = 1 then
Brace_Points.Clear;
Brace_Points.Append (Idx);
end if;
when ',' =>
if not Escaped and then Depth = 1 then
Brace_Points.Append (Idx);
end if;
when '}' =>
if not Escaped and then Depth = 1 and then Brace_Points.Length > 1 then
Braces_To_Parse.Clear;
Braces_To_Parse.Append_Vector (Brace_Points);
Braces_To_Parse.Append (Idx);
end if;
Depth := Depth - 1;
when others => null;
end case;
if Element (Str, Idx) /= '\' then
Escaped := False;
end if;
end loop;
if Braces_To_Parse.Length > 0 then
Prefix := Unbounded_Slice (Str, 1, Braces_To_Parse (0) - 1);
Suffix := Unbounded_Slice (Str, Braces_To_Parse.Last_Element + 1, Length (Str));
for Idx in 1 .. Braces_To_Parse.Length - 1 loop
Option := Unbounded_Slice (Str, Braces_To_Parse (Natural (Idx - 1)) + 1, Braces_To_Parse (Natural (Idx)) - 1);
Expand_Braces (Prefix & Option & Suffix);
end loop;
else
Put_Line (Str'Image);
end if;
end Expand_Braces;
function "+"(S : String) return Unbounded_String renames To_Unbounded_String;
begin
Expand_Braces (+"~/{Downloads,Pictures}/*.{jpg,gif,png}");
Expand_Braces (+"It{{em,alic}iz,erat}e{d,}, please.");
Expand_Braces (+"{,{,gotta have{ ,\, again\, }}more }cowbell!");
Expand_Braces (+"{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}");
end Brace_Expansion;
- Output:
"~/Downloads/*.jpg"
"~/Pictures/*.jpg"
"~/Downloads/*.gif"
"~/Pictures/*.gif"
"~/Downloads/*.png"
"~/Pictures/*.png"
"Itemized, please."
"Italicized, please."
"Iterated, please."
"Itemize, please."
"Italicize, please."
"Iterate, please."
"cowbell!"
"more cowbell!"
"gotta have more cowbell!"
"gotta have\, again\, more cowbell!"
"{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}"
"{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}"
AppleScript
This may seem like a cheat, but it is a legitimate and obvious way to tackle the problem with AppleScript in the unlikely event that the need should arise. It adjusts the escape levels in the input text, feeds it as a shell script to macOS's sh shell, and lets it handle the expansion.
use AppleScript version "2.4" -- OS X 10.10 (Yosemite) or later
use framework "Foundation"
use scripting additions
on braceExpansion(textForExpansion)
-- Massage the text to pass to a shell script: -
-- Single-quote it to render everything in it initially immune from brace and file-system expansion.
-- Include a return at the end to get a new line at the end of each eventual expansion.
set textForExpansion to quoted form of (textForExpansion & return)
-- Switch to ASObjC text for a couple of regex substitutions.
set textForExpansion to current application's class "NSMutableString"'s stringWithString:(textForExpansion)
-- Increase the escape level of every instance of /two/ backslashes (represented by eight in the
-- AppleScript string for the search regex) and isolate each result inside its own quote marks.
tell textForExpansion to replaceOccurrencesOfString:("\\\\\\\\") withString:("''$0$0''") ¬
options:(current application's NSRegularExpressionSearch) range:({0, its |length|()})
-- UNquote every run of braces and/or commas not now immediately preceded by a backslash.
tell textForExpansion to replaceOccurrencesOfString:("(?<!\\\\)[{,}]++") withString:("'$0'") ¬
options:(current application's NSRegularExpressionSearch) range:({0, its |length|()})
-- Pass the massaged text to a shell script to be 'echo'-ed. Since a space will still be inserted
-- between each expansion, also delete the space after each return in the result.
-- Return a list of the individual expansions.
return (do shell script ("echo " & textForExpansion & " | sed -E 's/([[:cntrl:]]) /\\1/g'"))'s paragraphs
end braceExpansion
-- Test:
set output to braceExpansion("~/{Downloads,Pictures}/*.{jpg,gif,png}") & ¬
braceExpansion("It{{em,alic}iz,erat}e{d,}, please.") & ¬
braceExpansion("{,{,gotta have{ ,\\, again\\, }}more }cowbell!") & ¬
braceExpansion("{}} some }{,{\\\\{ edge, edge} \\,}{ cases, {here} \\\\\\\\\\}")
set astid to AppleScript's text item delimiters
set AppleScript's text item delimiters to linefeed
set output to output as text
set AppleScript's text item delimiters to astid
log output -- To see the result without the backslash-escaping.
- Output:
(*~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}*)
AutoHotkey
;This one is a lot more simpler than the rest
BraceExp(string, del:="`n") {
Loop, Parse, string
if (A_LoopField = "{")
break
else
substring .= A_LoopField
substr := SubStr(string, InStr(string, "{")+1, InStr(string, "}")-InStr(string, "{")-1)
Loop, Parse, substr, `,
toreturn .= substring . A_LoopField . del
return toreturn
}
Msgbox, % BraceExp("enable_{video,audio}")
Msgbox, % BraceExp("apple {bush,tree}")
Msgbox, % BraceExp("h{i,ello}")
Msgbox, % BraceExp("rosetta{code,stone}")
- Output:
enable_video enable_audio apple bush apple tree hi hello rosettacode rosettastone
C
Handles only properly formed input.
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define BUFFER_SIZE 128
typedef unsigned char character;
typedef character *string;
typedef struct node_t node;
struct node_t {
enum tag_t {
NODE_LEAF,
NODE_TREE,
NODE_SEQ,
} tag;
union {
string str;
node *root;
} data;
node *next;
};
node *allocate_node(enum tag_t tag) {
node *n = malloc(sizeof(node));
if (n == NULL) {
fprintf(stderr, "Failed to allocate node for tag: %d\n", tag);
exit(1);
}
n->tag = tag;
n->next = NULL;
return n;
}
node *make_leaf(string str) {
node *n = allocate_node(NODE_LEAF);
n->data.str = str;
return n;
}
node *make_tree() {
node *n = allocate_node(NODE_TREE);
n->data.root = NULL;
return n;
}
node *make_seq() {
node *n = allocate_node(NODE_SEQ);
n->data.root = NULL;
return n;
}
void deallocate_node(node *n) {
if (n == NULL) {
return;
}
deallocate_node(n->next);
n->next = NULL;
if (n->tag == NODE_LEAF) {
free(n->data.str);
n->data.str = NULL;
} else if (n->tag == NODE_TREE || n->tag == NODE_SEQ) {
deallocate_node(n->data.root);
n->data.root = NULL;
} else {
fprintf(stderr, "Cannot deallocate node with tag: %d\n", n->tag);
exit(1);
}
free(n);
}
void append(node *root, node *elem) {
if (root == NULL) {
fprintf(stderr, "Cannot append to uninitialized node.");
exit(1);
}
if (elem == NULL) {
return;
}
if (root->tag == NODE_SEQ || root->tag == NODE_TREE) {
if (root->data.root == NULL) {
root->data.root = elem;
} else {
node *it = root->data.root;
while (it->next != NULL) {
it = it->next;
}
it->next = elem;
}
} else {
fprintf(stderr, "Cannot append to node with tag: %d\n", root->tag);
exit(1);
}
}
size_t count(node *n) {
if (n == NULL) {
return 0;
}
if (n->tag == NODE_LEAF) {
return 1;
}
if (n->tag == NODE_TREE) {
size_t sum = 0;
node *it = n->data.root;
while (it != NULL) {
sum += count(it);
it = it->next;
}
return sum;
}
if (n->tag == NODE_SEQ) {
size_t prod = 1;
node *it = n->data.root;
while (it != NULL) {
prod *= count(it);
it = it->next;
}
return prod;
}
fprintf(stderr, "Cannot count node with tag: %d\n", n->tag);
exit(1);
}
void expand(node *n, size_t pos) {
if (n == NULL) {
return;
}
if (n->tag == NODE_LEAF) {
printf(n->data.str);
} else if (n->tag == NODE_TREE) {
node *it = n->data.root;
while (true) {
size_t cnt = count(it);
if (pos < cnt) {
expand(it, pos);
break;
}
pos -= cnt;
it = it->next;
}
} else if (n->tag == NODE_SEQ) {
size_t prod = pos;
node *it = n->data.root;
while (it != NULL) {
size_t cnt = count(it);
size_t rem = prod % cnt;
expand(it, rem);
it = it->next;
}
} else {
fprintf(stderr, "Cannot expand node with tag: %d\n", n->tag);
exit(1);
}
}
string allocate_string(string src) {
size_t len = strlen(src);
string out = calloc(len + 1, sizeof(character));
if (out == NULL) {
fprintf(stderr, "Failed to allocate a copy of the string.");
exit(1);
}
strcpy(out, src);
return out;
}
node *parse_seq(string input, size_t *pos);
node *parse_tree(string input, size_t *pos) {
node *root = make_tree();
character buffer[BUFFER_SIZE] = { 0 };
size_t bufpos = 0;
size_t depth = 0;
bool asSeq = false;
bool allow = false;
while (input[*pos] != 0) {
character c = input[(*pos)++];
if (c == '\\') {
c = input[(*pos)++];
if (c == 0) {
break;
}
buffer[bufpos++] = '\\';
buffer[bufpos++] = c;
buffer[bufpos] = 0;
} else if (c == '{') {
buffer[bufpos++] = c;
buffer[bufpos] = 0;
asSeq = true;
depth++;
} else if (c == '}') {
if (depth-- > 0) {
buffer[bufpos++] = c;
buffer[bufpos] = 0;
} else {
if (asSeq) {
size_t new_pos = 0;
node *seq = parse_seq(buffer, &new_pos);
append(root, seq);
} else {
append(root, make_leaf(allocate_string(buffer)));
}
break;
}
} else if (c == ',') {
if (depth == 0) {
if (asSeq) {
size_t new_pos = 0;
node *seq = parse_seq(buffer, &new_pos);
append(root, seq);
bufpos = 0;
buffer[bufpos] = 0;
asSeq = false;
} else {
append(root, make_leaf(allocate_string(buffer)));
bufpos = 0;
buffer[bufpos] = 0;
}
} else {
buffer[bufpos++] = c;
buffer[bufpos] = 0;
}
} else {
buffer[bufpos++] = c;
buffer[bufpos] = 0;
}
}
return root;
}
node *parse_seq(string input, size_t *pos) {
node *root = make_seq();
character buffer[BUFFER_SIZE] = { 0 };
size_t bufpos = 0;
while (input[*pos] != 0) {
character c = input[(*pos)++];
if (c == '\\') {
c = input[(*pos)++];
if (c == 0) {
break;
}
buffer[bufpos++] = c;
buffer[bufpos] = 0;
} else if (c == '{') {
node *tree = parse_tree(input, pos);
if (bufpos > 0) {
append(root, make_leaf(allocate_string(buffer)));
bufpos = 0;
buffer[bufpos] = 0;
}
append(root, tree);
} else {
buffer[bufpos++] = c;
buffer[bufpos] = 0;
}
}
if (bufpos > 0) {
append(root, make_leaf(allocate_string(buffer)));
bufpos = 0;
buffer[bufpos] = 0;
}
return root;
}
void test(string input) {
size_t pos = 0;
node *n = parse_seq(input, &pos);
size_t cnt = count(n);
size_t i;
printf("Pattern: %s\n", input);
for (i = 0; i < cnt; i++) {
expand(n, i);
printf("\n");
}
printf("\n");
deallocate_node(n);
}
int main() {
test("~/{Downloads,Pictures}/*.{jpg,gif,png}");
test("It{{em,alic}iz,erat}e{d,}, please.");
test("{,{,gotta have{ ,\\, again\\, }}more }cowbell!");
//not sure how to parse this one
//test("{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}");
return 0;
}
- Output:
Pattern: ~/{Downloads,Pictures}/*.{jpg,gif,png}
~/Downloads/*.jpg
~/Pictures/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Downloads/*.gif
~/Pictures/*.png
Pattern: It{{em,alic}iz,erat}e{d,}, please.
Itemized, please.
Italicize, please.
Iterated, please.
Itemize, please.
Italicized, please.
Iterate, please.
Pattern: {,{,gotta have{ ,\, again\, }}more }cowbell!
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
C#
This approach turns the string into a tree structure, with Tokens that are either text, a concatenation or an alteration.
using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using static System.Linq.Enumerable;
public static class BraceExpansion
{
enum TokenType { OpenBrace, CloseBrace, Separator, Text, Alternate, Concat }
const char L = '{', R = '}', S = ',';
public static void Main() {
string[] input = {
"It{{em,alic}iz,erat}e{d,}, please.",
"~/{Downloads,Pictures}/*.{jpg,gif,png}",
@"{,{,gotta have{ ,\, again\, }}more }cowbell!",
@"{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}"
};
foreach (string text in input) Expand(text);
}
static void Expand(string input) {
Token token = Tokenize(input);
foreach (string value in token) Console.WriteLine(value);
Console.WriteLine();
}
static Token Tokenize(string input) {
var tokens = new List<Token>();
var buffer = new StringBuilder();
bool escaping = false;
int level = 0;
foreach (char c in input) {
(escaping, level, tokens, buffer) = c switch {
_ when escaping => (false, level, tokens, buffer.Append(c)),
'\\' => (true, level, tokens, buffer.Append(c)),
L => (escaping, level + 1,
tokens.With(buffer.Flush()).With(new Token(c.ToString(), TokenType.OpenBrace)), buffer),
S when level > 0 => (escaping, level,
tokens.With(buffer.Flush()).With(new Token(c.ToString(), TokenType.Separator)), buffer),
R when level > 0 => (escaping, level - 1,
tokens.With(buffer.Flush()).With(new Token(c.ToString(), TokenType.CloseBrace)).Merge(), buffer),
_ => (escaping, level, tokens, buffer.Append(c))
};
}
if (buffer.Length > 0) tokens.Add(buffer.Flush());
for (int i = 0; i < tokens.Count; i++) {
if (tokens[i].Type == TokenType.OpenBrace || tokens[i].Type == TokenType.Separator) {
tokens[i] = tokens[i].Value; //Change to text
}
}
return new Token(tokens, TokenType.Concat);
}
static List<Token> Merge(this List<Token> list) {
int separators = 0;
int last = list.Count - 1;
for (int i = list.Count - 3; i >= 0; i--) {
if (list[i].Type == TokenType.Separator) {
separators++;
Concat(list, i + 1, last);
list.RemoveAt(i);
last = i;
} else if (list[i].Type == TokenType.OpenBrace) {
Concat(list, i + 1, last);
if (separators > 0) {
list[i] = new Token(list.Range((i+1)..^1), TokenType.Alternate);
list.RemoveRange(i+1, list.Count - i - 1);
} else {
list[i] = L.ToString();
list[^1] = R.ToString();
Concat(list, i, list.Count);
}
break;
}
}
return list;
}
static void Concat(List<Token> list, int s, int e) {
for (int i = e - 2; i >= s; i--) {
(Token a, Token b) = (list[i], list[i+1]);
switch (a.Type, b.Type) {
case (TokenType.Text, TokenType.Text):
list[i] = a.Value + b.Value;
list.RemoveAt(i+1);
break;
case (TokenType.Concat, TokenType.Concat):
a.SubTokens.AddRange(b.SubTokens);
list.RemoveAt(i+1);
break;
case (TokenType.Concat, TokenType.Text) when b.Value == "":
list.RemoveAt(i+1);
break;
case (TokenType.Text, TokenType.Concat) when a.Value == "":
list.RemoveAt(i);
break;
default:
list[i] = new Token(new [] { a, b }, TokenType.Concat);
list.RemoveAt(i+1);
break;
}
}
}
private struct Token : IEnumerable<string>
{
private List<Token>? _subTokens;
public string Value { get; }
public TokenType Type { get; }
public List<Token> SubTokens => _subTokens ??= new List<Token>();
public Token(string value, TokenType type) => (Value, Type, _subTokens) = (value, type, null);
public Token(IEnumerable<Token> subTokens, TokenType type) => (Value, Type, _subTokens) = ("", type, subTokens.ToList());
public static implicit operator Token(string value) => new Token(value, TokenType.Text);
public IEnumerator<string> GetEnumerator() => (Type switch
{
TokenType.Concat => SubTokens.Select(t => t.AsEnumerable()).CartesianProduct().Select(p => string.Join("", p)),
TokenType.Alternate => from t in SubTokens from s in t select s,
_ => Repeat(Value, 1)
}).GetEnumerator();
IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
}
//===Extension methods===
static IEnumerable<IEnumerable<T>> CartesianProduct<T>(this IEnumerable<IEnumerable<T>> sequences) {
IEnumerable<IEnumerable<T>> emptyProduct = new[] { Empty<T>() };
return sequences.Aggregate(
emptyProduct,
(accumulator, sequence) =>
from acc in accumulator
from item in sequence
select acc.Concat(new [] { item }));
}
static List<Token> With(this List<Token> list, Token token) {
list.Add(token);
return list;
}
static IEnumerable<Token> Range(this List<Token> list, Range range) {
int start = range.Start.GetOffset(list.Count);
int end = range.End.GetOffset(list.Count);
for (int i = start; i < end; i++) yield return list[i];
}
static string Flush(this StringBuilder builder) {
string result = builder.ToString();
builder.Clear();
return result;
}
}
public static class BraceExpansion
{
const char L = '{', R = '}', S = ',';
//Main method same as above
static void Expand(string input) {
foreach (string s in GetItem(input).Item1) Console.WriteLine(s);
Console.WriteLine();
}
static (List<string>, string) GetItem(string s, int depth = 0) {
var output = new List<string> {""};
while (s.Length > 0) {
string c = s[..1];
if (depth > 0 && (c[0] == S || c[0] == R)) return (output, s);
if (c[0] == L) {
var x = GetGroup(s[1..], depth+1);
if (!(x.Item1 is null)) {
(output, s) = ((from a in output from b in x.Item1 select a + b).ToList(), x.Item2);
continue;
}
}
if (c[0] == '\\' && s.Length > 1) {
c += s[1];
s = s[1..];
}
(output, s) = ((from a in output select a + c).ToList(), s[1..]);
}
return (output, s);
}
static (List<string>?, string) GetGroup(string s, int depth) {
var output = new List<string>();
bool comma = false;
while (s.Length > 0) {
List<string>? g;
(g, s) = GetItem(s, depth);
if (s.Length == 0) break;
output.AddRange(g);
if (s[0] == R) {
if (comma) return (output, s[1..]);
return ((from a in output select L + a + R).ToList(), s[1..]);
}
if (s[0] == S) (comma, s) = (true, s[1..]);
}
return (null, "");
}
}
- Output:
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
C++
C++11 solution:
#include <iostream>
#include <iterator>
#include <string>
#include <utility>
#include <vector>
namespace detail {
template <typename ForwardIterator>
class tokenizer
{
ForwardIterator _tbegin, _tend, _end;
public:
tokenizer(ForwardIterator begin, ForwardIterator end)
: _tbegin(begin), _tend(begin), _end(end)
{ }
template <typename Lambda>
bool next(Lambda istoken)
{
if (_tbegin == _end) {
return false;
}
_tbegin = _tend;
for (; _tend != _end && !istoken(*_tend); ++_tend) {
if (*_tend == '\\' && std::next(_tend) != _end) {
++_tend;
}
}
if (_tend == _tbegin) {
_tend++;
}
return _tbegin != _end;
}
ForwardIterator begin() const { return _tbegin; }
ForwardIterator end() const { return _tend; }
bool operator==(char c) { return *_tbegin == c; }
};
template <typename List>
void append_all(List & lista, const List & listb)
{
if (listb.size() == 1) {
for (auto & a : lista) {
a += listb.back();
}
} else {
List tmp;
for (auto & a : lista) {
for (auto & b : listb) {
tmp.push_back(a + b);
}
}
lista = std::move(tmp);
}
}
template <typename String, typename List, typename Tokenizer>
List expand(Tokenizer & token)
{
std::vector<List> alts{ { String() } };
while (token.next([](char c) { return c == '{' || c == ',' || c == '}'; })) {
if (token == '{') {
append_all(alts.back(), expand<String, List>(token));
} else if (token == ',') {
alts.push_back({ String() });
} else if (token == '}') {
if (alts.size() == 1) {
for (auto & a : alts.back()) {
a = '{' + a + '}';
}
return alts.back();
} else {
for (std::size_t i = 1; i < alts.size(); i++) {
alts.front().insert(alts.front().end(),
std::make_move_iterator(std::begin(alts[i])),
std::make_move_iterator(std::end(alts[i])));
}
return std::move(alts.front());
}
} else {
for (auto & a : alts.back()) {
a.append(token.begin(), token.end());
}
}
}
List result{ String{ '{' } };
append_all(result, alts.front());
for (std::size_t i = 1; i < alts.size(); i++) {
for (auto & a : result) {
a += ',';
}
append_all(result, alts[i]);
}
return result;
}
} // namespace detail
template <
typename ForwardIterator,
typename String = std::basic_string<
typename std::iterator_traits<ForwardIterator>::value_type
>,
typename List = std::vector<String>
>
List expand(ForwardIterator begin, ForwardIterator end)
{
detail::tokenizer<ForwardIterator> token(begin, end);
List list{ String() };
while (token.next([](char c) { return c == '{'; })) {
if (token == '{') {
detail::append_all(list, detail::expand<String, List>(token));
} else {
for (auto & a : list) {
a.append(token.begin(), token.end());
}
}
}
return list;
}
template <
typename Range,
typename String = std::basic_string<typename Range::value_type>,
typename List = std::vector<String>
>
List expand(const Range & range)
{
using Iterator = typename Range::const_iterator;
return expand<Iterator, String, List>(std::begin(range), std::end(range));
}
int main()
{
for (std::string string : {
R"(~/{Downloads,Pictures}/*.{jpg,gif,png})",
R"(It{{em,alic}iz,erat}e{d,}, please.)",
R"({,{,gotta have{ ,\, again\, }}more }cowbell!)",
R"({}} some {\\{edge,edgy} }{ cases, here\\\})",
R"(a{b{1,2}c)",
R"(a{1,2}b}c)",
R"(a{1,{2},3}b)",
R"(a{b{1,2}c{}})",
R"(more{ darn{ cowbell,},})",
R"(ab{c,d\,e{f,g\h},i\,j{k,l\,m}n,o\,p}qr)",
R"({a,{\,b}c)",
R"(a{b,{{c}})",
R"({a{\}b,c}d)",
R"({a,b{{1,2}e}f)",
R"({}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\})",
R"({{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{)",
}) {
std::cout << string << '\n';
for (auto expansion : expand(string)) {
std::cout << " " << expansion << '\n';
}
std::cout << '\n';
}
return 0;
}
Common Lisp
(defstruct alternation
(alternatives nil :type list))
(defun alternatives-end-positions (string start)
(assert (char= (char string start) #\{))
(loop with level = 0
with end-positions
with escapep and commap
for index from start below (length string)
for c = (char string index)
do (cond (escapep
(setf escapep nil))
((char= c #\\)
(setf escapep t))
((char= c #\{)
(incf level))
((char= c #\})
(decf level)
(when (zerop level)
(push index end-positions)
(loop-finish)))
((and (char= c #\,) (= level 1))
(setf commap t)
(push index end-positions)))
finally (return (and (zerop level) commap (nreverse end-positions)))))
(defun parse-alternation (string start)
(loop with end-positions = (alternatives-end-positions string start)
for %start = (1+ start) then (1+ %end)
for %end in end-positions
collect (parse string :start %start :end %end) into alternatives
finally (return (and alternatives
(values (make-alternation :alternatives alternatives) (1+ %end))))))
(defun parse (string &key (start 0) (end (length string)))
(loop with result and escapep
for index = start then next
while (< index end)
for c = (char string index)
for next = (1+ index)
do (cond (escapep
(push c result)
(setf escapep nil))
((char= c #\\)
(push c result)
(setf escapep t))
((char= c #\{)
(multiple-value-bind (alternation next-index)
(parse-alternation string index)
(cond (alternation
(push alternation result)
(setf next next-index))
(t
(push c result)))))
(t
(push c result)))
finally (return (nreverse result))))
(defun traverse-alternation (alternation)
(mapcan #'traverse (alternation-alternatives alternation)))
(defun traverse (parsed)
(let ((results (list nil)))
(dolist (element parsed results)
(etypecase element
(character
(setf results (loop for r in results
collect (nconc r (list element)))))
(alternation
(setf results (loop for r in results
nconc (loop for ar in (traverse-alternation element)
collect (append r ar)))))))))
(defun expand (string)
(loop for result in (traverse (parse string))
collect (coerce result 'string)))
(defun main ()
(dolist (input '("~/{Downloads,Pictures}/*.{jpg,gif,png}"
"It{{em,alic}iz,erat}e{d,}, please."
"{,{,gotta have{ ,\\, again\\, }}more }cowbell!"
"{}} some }{,{\\\\{ edge, edge} \\,}{ cases, {here} \\\\\\\\\\}"))
(write-line input)
(dolist (output (expand input))
(format t " ~A~%" output))
(terpri)))
- Output:
~/{Downloads,Pictures}/*.{jpg,gif,png}
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
It{{em,alic}iz,erat}e{d,}, please.
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
D
This code is not UTF-corrected, because it uses slicing instead of front, popFront, etc.
import std.stdio, std.typecons, std.array, std.range, std.algorithm, std.string;
Nullable!(Tuple!(string[], string)) getGroup(string s, in uint depth)
pure nothrow @safe {
string[] sout;
auto comma = false;
while (!s.empty) {
// {const g, s} = getItems(s, depth);
const r = getItems(s, depth);
const g = r[0];
s = r[1];
if (s.empty)
break;
sout ~= g;
if (s[0] == '}') {
if (comma)
return typeof(return)(tuple(sout, s[1 .. $]));
return typeof(return)(tuple(
sout.map!(a => '{' ~ a ~ '}').array, s[1 .. $]));
}
if (s[0] == ',') {
comma = true;
s = s[1 .. $];
}
}
return typeof(return)();
}
Tuple!(string[], string) getItems(string s, in uint depth=0) pure @safe nothrow {
auto sout = [""];
while (!s.empty) {
auto c = s[0 .. 1];
if (depth && (c == "," || c == "}"))
return tuple(sout, s);
if (c == "{") {
/*const*/ auto x = getGroup(s.dropOne, depth + 1);
if (!x.isNull) {
sout = cartesianProduct(sout, x[0])
.map!(ab => ab[0] ~ ab[1])
.array;
s = x[1];
continue;
}
}
if (c == "\\" && s.length > 1) {
c ~= s[1];
s = s[1 .. $];
}
sout = sout.map!(a => a ~ c).array;
s = s[1 .. $];
}
return tuple(sout, s);
}
void main() @safe {
immutable testCases = r"~/{Downloads,Pictures}/*.{jpg,gif,png}
It{{em,alic}iz,erat}e{d,}, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
a{b{1,2}c
a{1,2}b}c
a{1,{2},3}b
a{b{1,2}c{}}
more{ darn{ cowbell,},}
ab{c,d\,e{f,g\h},i\,j{k,l\,m}n,o\,p}qr
{a,{\,b}c
a{b,{{c}}
{a{\}b,c}d
{a,b{{1,2}e}f";
foreach (const s; testCases.splitLines)
writefln("%s\n%-( %s\n%)\n", s, s.getItems[0]);
}
- Output:
~/{Downloads,Pictures}/*.{jpg,gif,png}
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
It{{em,alic}iz,erat}e{d,}, please.
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
a{b{1,2}c
a{b1c
a{b2c
a{1,2}b}c
a1b}c
a2b}c
a{1,{2},3}b
a1b
a{2}b
a3b
a{b{1,2}c{}}
a{b1c{}}
a{b2c{}}
more{ darn{ cowbell,},}
more darn cowbell
more darn
more
ab{c,d\,e{f,g\h},i\,j{k,l\,m}n,o\,p}qr
abcqr
abd\,efqr
abd\,eg\hqr
abi\,jknqr
abi\,jl\,mnqr
abo\,pqr
{a,{\,b}c
{a,{\,b}c
a{b,{{c}}
a{b,{{c}}
{a{\}b,c}d
{a\}bd
{acd
{a,b{{1,2}e}f
{a,b{1e}f
{a,b{2e}f
EasyLang
procdecl getgroup depth . out$[] s$ ok .
proc getitem depth . s$ out$[] .
out$[] = [ "" ]
while s$ <> ""
c$ = substr s$ 1 1
if depth > 0 and (c$ = "," or c$ = "}")
return
.
s$ = substr s$ 2 9999
isgroup = 0
if c$ = "{"
s0$ = s$
getgroup depth + 1 og$[] s$ isgroup
if isgroup = 1
outn$[] = [ ]
for o1$ in out$[]
for o2$ in og$[]
outn$[] &= o1$ & o2$
.
.
swap out$[] outn$[]
else
s$ = s0$
.
.
if isgroup = 0
if c$ = "\\"
c$ = substr s$ 1 1
s$ = substr s$ 2 9999
.
for i to len out$[]
out$[i] &= c$
.
.
.
.
proc getgroup depth . out$[] s$ ok .
out$[] = [ ]
while s$ <> ""
getitem depth s$ g$[]
for g$ in g$[]
out$[] &= g$
.
c$ = substr s$ 1 1
if c$ = "}"
s$ = substr s$ 2 9999
if comma = 0
for i to len out$[]
out$[i] = "{" & out$[i] & "}"
.
.
ok = 1
return
.
if c$ = ","
comma = 1
s$ = substr s$ 2 9999
.
.
ok = 0
.
repeat
s$ = input
until s$ = ""
print s$ & " ->"
getitem 0 s$ r$[]
for r$ in r$[]
print r$
.
print ""
.
#
input_data
~/{Downloads,Pictures}/*.{jpg,gif,png}
It{{em,alic}iz,erat}e{d,}, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
- Output:
~/{Downloads,Pictures}/*.{jpg,gif,png} ->
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
It{{em,alic}iz,erat}e{d,}, please. ->
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
{,{,gotta have{ ,\, again\, }}more }cowbell! ->
cowbell!
more cowbell!
gotta have more cowbell!
gotta have, again, more cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\} ->
{}} some }{,{\ edge ,}{ cases, {here} \\}
{}} some }{,{\ edge ,}{ cases, {here} \\}
Ed
Only replaces one instance of brace expression. Doesn't replace the nested ones. Doesn't take escaping into account. Still, ed was not intended for that but it does work with it, however simplistic that might be.
H
t
1s/(\{[^}]*\})/%REPLACEME%/
2s/[^{]*\{([^}]*)\}.*/\1/
2s/,/\
/g
2,$g/(.*)/1y\
-1x\
+1s/^/|/\
-1,.j\
s/(.*)%REPLACEME%(.*)\|(.*)/\1\3\2/
1d
,p
Q- Output:
$ cat brace.input
~/{Downloads,Pictures}/*.{jpg,gif,png}
$ cat brace.ed | ed -E brace.input
Newline appended
39
~/Downloads/*.{jpg,gif,png}
~/Pictures/*.{jpg,gif,png}
?
Warning: buffer modified
Elixir
defmodule Brace_expansion do
def getitem(s), do: getitem(String.codepoints(s), 0, [""])
defp getitem([], _, out), do: {out,[]}
defp getitem([c|_]=s, depth, out) when depth>0 and (c == "," or c == "}"), do: {out,s}
defp getitem([c|t], depth, out) do
x = getgroup(t, depth+1, [], false)
if (c == "{") and x do
{y, z} = x
out2 = for a <- out, b <- y, do: a<>b
getitem(z, depth, out2)
else
if c == "\\" and length(t) > 0 do
c2 = c <> hd(t)
getitem(tl(t), depth, Enum.map(out, fn a -> a <> c2 end))
else
getitem(t, depth, Enum.map(out, fn a -> a <> c end))
end
end
end
defp getgroup([], _, _, _), do: nil
defp getgroup(s, depth, out, comma) do
{g, s2} = getitem(s, depth, [""])
if s2 == [] do
nil
else
out2 = out ++ g
case hd(s2) do
"}" -> if comma, do: {out2, tl(s2)},
else: {Enum.map(out2, &"{#{&1}}"), tl(s2)}
"," -> getgroup(tl(s2), depth, out2, true)
_ -> getgroup(s2, depth, out2, comma)
end
end
end
end
test_cases = ~S"""
~/{Downloads,Pictures}/*.{jpg,gif,png}
It{{em,alic}iz,erat}e{d,}, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
""" |> String.split("\n", trim: true)
Enum.each(test_cases, fn s ->
IO.puts s
Brace_expansion.getitem(s)
|> elem(0)
|> Enum.each(fn str -> IO.puts "\t#{str}" end)
IO.puts ""
end)
- Output:
~/{Downloads,Pictures}/*.{jpg,gif,png}
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
It{{em,alic}iz,erat}e{d,}, please.
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
Go
expand.go:
package expand
// Expander is anything that can be expanded into a slice of strings.
type Expander interface {
Expand() []string
}
// Text is a trivial Expander that expands to a slice with just itself.
type Text string
func (t Text) Expand() []string { return []string{string(t)} }
// Alternation is an Expander that expands to the union of its
// members' expansions.
type Alternation []Expander
func (alt Alternation) Expand() []string {
var out []string
for _, e := range alt {
out = append(out, e.Expand()...)
}
return out
}
// Sequence is an Expander that expands to the combined sequence of its
// members' expansions.
type Sequence []Expander
func (seq Sequence) Expand() []string {
if len(seq) == 0 {
return nil
}
out := seq[0].Expand()
for _, e := range seq[1:] {
out = combine(out, e.Expand())
}
return out
}
func combine(al, bl []string) []string {
out := make([]string, 0, len(al)*len(bl))
for _, a := range al {
for _, b := range bl {
out = append(out, a+b)
}
}
return out
}
// Currently only single byte runes are supported for these.
const (
escape = '\\'
altStart = '{'
altEnd = '}'
altSep = ','
)
type piT struct{ pos, cnt, depth int }
type Brace string
// Expand takes an input string and returns the expanded list of
// strings. The input string can contain any number of nested
// alternation specifications of the form "{A,B}" which is expanded to
// the strings "A", then "B".
//
// E.g. Expand("a{2,1}b{X,Y,X}c") returns ["a2bXc", "a2bYc", "a2bXc",
// "a1bXc", "a1bYc", "a1bXc"].
//
// Unmatched '{', ',', and '}' characters are passed through to the
// output. The special meaning of these characters can be escaped with
// '\', (which itself can be escaped).
// Escape characters are not removed, but passed through to the output.
func Expand(s string) []string { return Brace(s).Expand() }
func (b Brace) Expand() []string { return b.Expander().Expand() }
func (b Brace) Expander() Expander {
s := string(b)
//log.Printf("Exapand(%#q)\n", s)
var posInfo []piT
var stack []int // indexes into posInfo
removePosInfo := func(i int) {
end := len(posInfo) - 1
copy(posInfo[i:end], posInfo[i+1:])
posInfo = posInfo[:end]
}
inEscape := false
for i, r := range s {
if inEscape {
inEscape = false
continue
}
switch r {
case escape:
inEscape = true
case altStart:
stack = append(stack, len(posInfo))
posInfo = append(posInfo, piT{i, 0, len(stack)})
case altEnd:
if len(stack) == 0 {
continue
}
si := len(stack) - 1
pi := stack[si]
if posInfo[pi].cnt == 0 {
removePosInfo(pi)
for pi < len(posInfo) {
if posInfo[pi].depth == len(stack) {
removePosInfo(pi)
} else {
pi++
}
}
} else {
posInfo = append(posInfo, piT{i, -2, len(stack)})
}
stack = stack[:si]
case altSep:
if len(stack) == 0 {
continue
}
posInfo = append(posInfo, piT{i, -1, len(stack)})
posInfo[stack[len(stack)-1]].cnt++
}
}
//log.Println("stack:", stack)
for len(stack) > 0 {
si := len(stack) - 1
pi := stack[si]
depth := posInfo[pi].depth
removePosInfo(pi)
for pi < len(posInfo) {
if posInfo[pi].depth == depth {
removePosInfo(pi)
} else {
pi++
}
}
stack = stack[:si]
}
return buildExp(s, 0, posInfo)
}
func buildExp(s string, off int, info []piT) Expander {
if len(info) == 0 {
return Text(s)
}
//log.Printf("buildExp(%#q, %d, %v)\n", s, off, info)
var seq Sequence
i := 0
var dj, j, depth int
for dk, piK := range info {
k := piK.pos - off
switch s[k] {
case altStart:
if depth == 0 {
dj = dk
j = k
depth = piK.depth
}
case altEnd:
if piK.depth != depth {
continue
}
if j > i {
seq = append(seq, Text(s[i:j]))
}
alt := buildAlt(s[j+1:k], depth, j+1+off, info[dj+1:dk])
seq = append(seq, alt)
i = k + 1
depth = 0
}
}
if j := len(s); j > i {
seq = append(seq, Text(s[i:j]))
}
if len(seq) == 1 {
return seq[0]
}
return seq
}
func buildAlt(s string, depth, off int, info []piT) Alternation {
//log.Printf("buildAlt(%#q, %d, %d, %v)\n", s, depth, off, info)
var alt Alternation
i := 0
var di int
for dk, piK := range info {
if piK.depth != depth {
continue
}
if k := piK.pos - off; s[k] == altSep {
sub := buildExp(s[i:k], i+off, info[di:dk])
alt = append(alt, sub)
i = k + 1
di = dk + 1
}
}
sub := buildExp(s[i:], i+off, info[di:])
alt = append(alt, sub)
return alt
}
expand_test.go
package expand
import (
"fmt"
"reflect"
"testing"
)
// These could be in expand.go but for now they're only used for debugging.
func (t Text) String() string { return fmt.Sprintf("%#q", string(t)) }
func (alt Alternation) String() string { return fmt.Sprintf("ALT:%v", []Expander(alt)) }
// From http://rosettacode.org/wiki/Brace_expansion
var testCases = []struct {
input string
expected []string
}{
{"", []string{""}},
{"a{2,1}b{X,Y,X}c", []string{
"a2bXc",
"a2bYc",
"a2bXc",
"a1bXc",
"a1bYc",
"a1bXc"}},
{`a\\{\\\{b,c\,d}`, []string{
`a\\\\\{b`,
`a\\c\,d`}},
{"{a,b{c{,{d}}e}f", []string{
"{a,b{ce}f",
"{a,b{c{d}e}f"}},
{"~/{Downloads,Pictures}/*.{jpg,gif,png}", []string{
"~/Downloads/*.jpg",
"~/Downloads/*.gif",
"~/Downloads/*.png",
"~/Pictures/*.jpg",
"~/Pictures/*.gif",
"~/Pictures/*.png"}},
{"It{{em,alic}iz,erat}e{d,}, please.", []string{
"Itemized, please.",
"Itemize, please.",
"Italicized, please.",
"Italicize, please.",
"Iterated, please.",
"Iterate, please."}},
{`{,{,gotta have{ ,\, again\, }}more }cowbell!`, []string{
"cowbell!",
"more cowbell!",
"gotta have more cowbell!",
`gotta have\, again\, more cowbell!`}},
{`{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}`, []string{
`{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}`,
`{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}`}},
}
//func ml(l []string) string { return "\n\t" + strings.Join(l, "\n\t") }
func ml(l []string) string {
var result string
for _, s := range l {
result += fmt.Sprintf("\n\t%#q", s)
}
return result
}
func TestExpand(t *testing.T) {
for _, d := range testCases {
if g := Expand(d.input); !reflect.DeepEqual(g, d.expected) {
t.Errorf("unexpected result\n Expand(%#q) gave:%v\nExpected:%v",
d.input, ml(g), ml(d.expected))
} else {
// Normally Go tests aren't this verbose, but for rosettacode
t.Logf("as expected\n Expand(%#q):%v", d.input, ml(g))
}
}
}
func BenchmarkExpand(b *testing.B) {
input := testCases[5].input
//b.Logf("Benchmarking Expand(%#q)\n", input)
b.ReportAllocs()
for i := 0; i < b.N; i++ {
Expand(input)
}
}
- Output:
% go test -v -bench=.
=== RUN TestExpand
--- PASS: TestExpand (0.00 seconds)
expand_test.go:72: as expected
Expand(``):
``
expand_test.go:72: as expected
Expand(`a{2,1}b{X,Y,X}c`):
`a2bXc`
`a2bYc`
`a2bXc`
`a1bXc`
`a1bYc`
`a1bXc`
expand_test.go:72: as expected
Expand(`a\\{\\\{b,c\,d}`):
`a\\\\\{b`
`a\\c\,d`
expand_test.go:72: as expected
Expand(`{a,b{c{,{d}}e}f`):
`{a,b{ce}f`
`{a,b{c{d}e}f`
expand_test.go:72: as expected
Expand(`~/{Downloads,Pictures}/*.{jpg,gif,png}`):
`~/Downloads/*.jpg`
`~/Downloads/*.gif`
`~/Downloads/*.png`
`~/Pictures/*.jpg`
`~/Pictures/*.gif`
`~/Pictures/*.png`
expand_test.go:72: as expected
Expand(`It{{em,alic}iz,erat}e{d,}, please.`):
`Itemized, please.`
`Itemize, please.`
`Italicized, please.`
`Italicize, please.`
`Iterated, please.`
`Iterate, please.`
expand_test.go:72: as expected
Expand(`{,{,gotta have{ ,\, again\, }}more }cowbell!`):
`cowbell!`
`more cowbell!`
`gotta have more cowbell!`
`gotta have\, again\, more cowbell!`
expand_test.go:72: as expected
Expand(`{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}`):
`{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}`
`{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}`
PASS
BenchmarkExpand 500000 6562 ns/op 2467 B/op 64 allocs/op
ok rosetta_code/Brace_expansion 3.347s
Groovy
class BraceExpansion {
static void main(String[] args) {
for (String s : [
"It{{em,alic}iz,erat}e{d,}, please.",
"~/{Downloads,Pictures}/*.{jpg,gif,png}",
"{,{,gotta have{ ,\\, again\\, }}more }cowbell!",
"{}} some }{,{\\\\{ edge, edge} \\,}{ cases, {here} \\\\\\\\\\}"
]) {
println()
expand(s)
}
}
static void expand(String s) {
expandR("", s, "")
}
private static void expandR(String pre, String s, String suf) {
int i1 = -1, i2 = 0
String noEscape = s.replaceAll("([\\\\]{2}|[\\\\][,}{])", " ")
StringBuilder sb = null
outer:
while ((i1 = noEscape.indexOf('{', i1 + 1)) != -1) {
i2 = i1 + 1
sb = new StringBuilder(s)
for (int depth = 1; i2 < s.length() && depth > 0; i2++) {
char c = noEscape.charAt(i2)
depth = (c == ('{' as char)) ? ++depth : depth
depth = (c == ('}' as char)) ? --depth : depth
if (c == (',' as char) && depth == 1) {
sb.setCharAt(i2, '\u0000' as char)
} else if (c == ('}' as char) && depth == 0 && sb.indexOf("\u0000") != -1) {
break outer
}
}
}
if (i1 == -1) {
if (suf.length() > 0) {
expandR(pre + s, suf, "")
} else {
printf("%s%s%s%n", pre, s, suf)
}
} else {
for (String m : sb.substring(i1 + 1, i2).split("\u0000", -1)) {
expandR(pre + s.substring(0, i1), m, s.substring(i2 + 1) + suf)
}
}
}
}
- Output:
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
Haskell
"Here is a direct translation to Haskell using parsec" (of an earlier version of the Raku solution):
import qualified Text.Parsec as P
showExpansion :: String -> String
showExpansion =
(<>) . (<> "\n-->\n") <*> (either show unlines . P.parse parser [])
parser :: P.Parsec String u [String]
parser = expansion P.anyChar
expansion :: P.Parsec String u Char -> P.Parsec String u [String]
expansion =
fmap expand .
P.many .
((P.try alts P.<|> P.try alt1 P.<|> escape) P.<|>) . fmap (pure . pure)
expand :: [[String]] -> [String]
expand = foldr ((<*>) . fmap (<>)) [[]]
alts :: P.Parsec String u [String]
alts = concat <$> P.between (P.char '{') (P.char '}') (alt `sepBy2` P.char ',')
alt :: P.Parsec String u [String]
alt = expansion (P.noneOf ",}")
alt1 :: P.Parsec String u [String]
alt1 =
(\x -> ['{' : (x <> "}")]) <$>
P.between (P.char '{') (P.char '}') (P.many $ P.noneOf ",{}")
sepBy2 :: P.Parsec String u a -> P.Parsec String u b -> P.Parsec String u [a]
p `sepBy2` sep = (:) <$> p <*> P.many1 (sep >> p)
escape :: P.Parsec String u [String]
escape = pure <$> sequence [P.char '\\', P.anyChar]
main :: IO ()
main =
mapM_
(putStrLn . showExpansion)
[ "~/{Downloads,Pictures}/*.{jpg,gif,png}"
, "It{{em,alic}iz,erat}e{d,}, please."
, "{,{,gotta have{ ,\\, again\\, }}more }cowbell!"
, "{}} some }{,{\\\\{ edge, edge} \\,}{ cases, {here} \\\\\\\\\\}"
]
- Output:
It{{em,alic}iz,erat}e{d,}, please.
-->
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
-->
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
-->
{}} some }{ cases, {here} \\\\\}
{}} some }{\\ edge \,{ cases, {here} \\\\\}
{}} some }{\\ edge \,{ cases, {here} \\\\\}
J
Implementation:
NB. legit { , and } do not follow a legit backslash:
legit=: 1,_1}.4>(3;(_2[\"1".;._2]0 :0);('\';a.);0 _1 0 1)&;:&.(' '&,)
2 1 1 1 NB. result 0 or 1: initial state
2 2 1 2 NB. result 2 or 3: after receiving a non backslash
1 2 1 2 NB. result 4 or 5: after receiving a backslash
)
expand=:3 :0
Ch=. u:inv y
M=. N=. 1+>./ Ch
Ch=. Ch*-_1^legit y
delim=. 'left comma right'=. u:inv '{,}'
J=. i.K=. #Ch
while. M=. M+1 do.
candidates=. i.0 2
for_check.I. comma=Ch do.
begin=. >./I. left=check{. Ch
end=. check+<./I. right=check}. Ch
if. K>:end-begin do.
candidates=. candidates,begin,end
end.
end.
if. 0=#candidates do. break. end.
'begin end'=. candidates{~(i.>./) -/"1 candidates
ndx=. I.(begin<:J)*(end>:J)*Ch e. delim
Ch=. M ndx} Ch
end.
T=. ,<Ch
for_mark. |.N}.i.M do.
T=. ; mark divide each T
end.
u: each |each T
)
divide=:4 :0
if. -.x e. y do. ,<y return. end.
mask=. x=y
prefix=. < y #~ -.+./\ mask
suffix=. < y #~ -.+./\. mask
options=. }:mask <;._1 y
prefix,each options,each suffix
)
Examples:
>expand t1
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
> expand t2
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
>expand t3
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
>expand t4
{}} some {\\edge }{ cases, here\\\}
{}} some {\\edgy }{ cases, here\\\}
Explanation:
Instead of working directly with text, work with a string of numeric unicode values. Negate the numbers for characters which are "off limits" because of preceding backslashes (we will take the absolute value and convert back to unicode for the final result). Also, find a limit value larger than that of the largest in-use character.
Then, iteratively: for each relevant comma, find the location of the closest surrounding braces. From these candidates, pick a pair of braces that's the shortest distance apart. Mark those braces and their contained relevant commas by replacing their character codes with an integer larger than any previously used (all of them in the set get marked with the same number). Repeat until we cannot find any more possibilities.
Finally, for each integer that we've used to mark delimiter locations, split out each of the marked options (each with a copy of that group's prefix and suffix). (Then when all that is done, take the absolute values convert back to unicode for the final result.)
Java
Should be able to handle all printable Unicode.
public class BraceExpansion {
public static void main(String[] args) {
for (String s : new String[]{"It{{em,alic}iz,erat}e{d,}, please.",
"~/{Downloads,Pictures}/*.{jpg,gif,png}",
"{,{,gotta have{ ,\\, again\\, }}more }cowbell!",
"{}} some }{,{\\\\{ edge, edge} \\,}{ cases, {here} \\\\\\\\\\}"}) {
System.out.println();
expand(s);
}
}
public static void expand(String s) {
expandR("", s, "");
}
private static void expandR(String pre, String s, String suf) {
int i1 = -1, i2 = 0;
String noEscape = s.replaceAll("([\\\\]{2}|[\\\\][,}{])", " ");
StringBuilder sb = null;
outer:
while ((i1 = noEscape.indexOf('{', i1 + 1)) != -1) {
i2 = i1 + 1;
sb = new StringBuilder(s);
for (int depth = 1; i2 < s.length() && depth > 0; i2++) {
char c = noEscape.charAt(i2);
depth = (c == '{') ? ++depth : depth;
depth = (c == '}') ? --depth : depth;
if (c == ',' && depth == 1) {
sb.setCharAt(i2, '\u0000');
} else if (c == '}' && depth == 0 && sb.indexOf("\u0000") != -1)
break outer;
}
}
if (i1 == -1) {
if (suf.length() > 0)
expandR(pre + s, suf, "");
else
System.out.printf("%s%s%s%n", pre, s, suf);
} else {
for (String m : sb.substring(i1 + 1, i2).split("\u0000", -1))
expandR(pre + s.substring(0, i1), m, s.substring(i2 + 1) + suf);
}
}
}
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
JavaScript
ES5 Functional
Without importing Node.js libraries, JavaScript doesn't immediately have access to anything like Haskell's Parsec, but using a functional idiom of JavaScript, and emphasising clarity more than optimisation, we can separate out the tokenizing from the parsing, and the parsing from the generation of strings, to build a function which:
- returns the set of expansions for each brace expression, and
- logs a pretty-printed abstract syntax tree for each expression to the console (in a JSON format).
Each node of the parse tree consists of one of two simple functions (AND: syntagmatic concatenation, OR: flattening of paradigms) with a set of arguments, each of which may be a plain string or an AND or OR subtree. The expansions are derived by evaluating the parse tree as an expression.
(function () {
'use strict'
// Index of any closing brace matching the opening
// brace at iPosn,
// with the indices of any immediately-enclosed commas.
function bracePair(tkns, iPosn, iNest, lstCommas) {
if (iPosn >= tkns.length || iPosn < 0) return null;
var t = tkns[iPosn],
n = (t === '{') ? (
iNest + 1
) : (t === '}' ? (
iNest - 1
) : iNest),
lst = (t === ',' && iNest === 1) ? (
lstCommas.concat(iPosn)
) : lstCommas;
return n ? bracePair(tkns, iPosn + 1, n, lst) : {
close: iPosn,
commas: lst
};
}
// Parse of a SYNTAGM subtree
function andTree(dctSofar, tkns) {
if (!tkns.length) return [dctSofar, []];
var dctParse = dctSofar ? dctSofar : {
fn: and,
args: []
},
head = tkns[0],
tail = head ? tkns.slice(1) : [],
dctBrace = head === '{' ? bracePair(
tkns, 0, 0, []
) : null,
lstOR = dctBrace && (
dctBrace.close
) && dctBrace.commas.length ? (
splitAt(dctBrace.close + 1, tkns)
) : null;
return andTree({
fn: and,
args: dctParse.args.concat(
lstOR ? (
orTree(dctParse, lstOR[0], dctBrace.commas)
) : head
)
}, lstOR ? (
lstOR[1]
) : tail);
}
// Parse of a PARADIGM subtree
function orTree(dctSofar, tkns, lstCommas) {
if (!tkns.length) return [dctSofar, []];
var iLast = lstCommas.length;
return {
fn: or,
args: splitsAt(
lstCommas, tkns
).map(function (x, i) {
var ts = x.slice(
1, i === iLast ? (
-1
) : void 0
);
return ts.length ? ts : [''];
}).map(function (ts) {
return ts.length > 1 ? (
andTree(null, ts)[0]
) : ts[0];
})
};
}
// List of unescaped braces and commas, and remaining strings
function tokens(str) {
// Filter function excludes empty splitting artefacts
var toS = function (x) {
return x.toString();
};
return str.split(/(\\\\)/).filter(toS).reduce(function (a, s) {
return a.concat(s.charAt(0) === '\\' ? s : s.split(
/(\\*[{,}])/
).filter(toS));
}, []);
}
// PARSE TREE OPERATOR (1 of 2)
// Each possible head * each possible tail
function and(args) {
var lng = args.length,
head = lng ? args[0] : null,
lstHead = "string" === typeof head ? (
[head]
) : head;
return lng ? (
1 < lng ? lstHead.reduce(function (a, h) {
return a.concat(
and(args.slice(1)).map(function (t) {
return h + t;
})
);
}, []) : lstHead
) : [];
}
// PARSE TREE OPERATOR (2 of 2)
// Each option flattened
function or(args) {
return args.reduce(function (a, b) {
return a.concat(b);
}, []);
}
// One list split into two (first sublist length n)
function splitAt(n, lst) {
return n < lst.length + 1 ? [
lst.slice(0, n), lst.slice(n)
] : [lst, []];
}
// One list split into several (sublist lengths [n])
function splitsAt(lstN, lst) {
return lstN.reduceRight(function (a, x) {
return splitAt(x, a[0]).concat(a.slice(1));
}, [lst]);
}
// Value of the parse tree
function evaluated(e) {
return typeof e === 'string' ? e :
e.fn(e.args.map(evaluated));
}
// JSON prettyprint (for parse tree, token list etc)
function pp(e) {
return JSON.stringify(e, function (k, v) {
return typeof v === 'function' ? (
'[function ' + v.name + ']'
) : v;
}, 2)
}
// ----------------------- MAIN ------------------------
// s -> [s]
function expansions(s) {
// BRACE EXPRESSION PARSED
var dctParse = andTree(null, tokens(s))[0];
// ABSTRACT SYNTAX TREE LOGGED
console.log(pp(dctParse));
// AST EVALUATED TO LIST OF STRINGS
return evaluated(dctParse);
}
// Sample expressions,
// double-escaped for quotation in source code.
var lstTests = [
'~/{Downloads,Pictures}/*.{jpg,gif,png}',
'It{{em,alic}iz,erat}e{d,}, please.',
'{,{,gotta have{ ,\\, again\\, }}more }cowbell!',
'{}} some }{,{\\\\{ edge, edge} \\,}{ cases, {here} \\\\\\\\\\}'
];
// 1. Return each expression with an indented list of its expansions, while
// 2. logging each parse tree to the console.log() stream
return lstTests.map(function (s) {
return s + '\n\n' + expansions(s).map(function (x) {
return ' ' + x;
}).join('\n');
}).join('\n\n');
})();
Value returned by function:
~/{Downloads,Pictures}/*.{jpg,gif,png}
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
It{{em,alic}iz,erat}e{d,}, please.
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
Sample of parse trees logged to the console:
{
"fn": "[function and]",
"args": [
"It",
{
"fn": "[function or]",
"args": [
{
"fn": "[function and]",
"args": [
{
"fn": "[function or]",
"args": [
"em",
"alic"
]
},
"iz"
]
},
"erat"
]
},
"e",
{
"fn": "[function or]",
"args": [
"d",
""
]
},
",",
" please."
]
}
jq
Adapted from Wren
Also works with gojq, the Go implementation of jq
# Input: a string
# Emit an array of the expansions
def expand:
# Emit [ array, string ]
def getItem($depth):
def getGroup($depth):
{ out: [], comma: false, s: . }
| until (.s == "" or .return;
(.s | getItem($depth)) as $t
| $t[0] as $g
| .s = $t[1]
| if .s == "" then .return = [[], ""]
else .out += $g
| if .s[0:1] == "}"
then if .comma then .return = [.out, .s[1:]]
else .return = [ (.out | map( "{" + . + "}" )), .s[1:]]
end
else if .s[0:1] == ","
then .comma = true
| .s |= .[1:]
else .
end
end
end)
| if .return then .return else [[], ""] end ;
{ out: [""], s: .}
| until( (.s == "") or .return;
.c = .s[0:1]
| if ($depth > 0) and (.c == "," or .c == "}")
then .return = [.out, .s]
else .cont = false
| if .c == "{"
then (.s[1:] | getGroup($depth+1)) as $x
| if $x[0] | length > 0
# conform to the "lexicographic" ordering requirement
then .out |= [ .[] as $o | $o + $x[0][] ]
| .s = $x[1]
| .cont = true
else .
end
else .
end
end
| if (.cont | not)
then if (.c == "\\") and ((.s|length) > 1)
then .c += .s[1:2]
| .s |= .[1:]
else .
end
| .out = [.out[] + .c]
| .s |= .[1:]
else .
end )
| if .return then .return else [.out, .s] end ;
getItem(0)[0];
def inputs: [
"~/{Downloads,Pictures}/*.{jpg,gif,png}",
"It{{em,alic}iz,erat}e{d,}, please.",
"{,{,gotta have{ ,\\, again\\, }}more }cowbell!",
"{}} some }{,{\\\\{ edge, edge} \\,}{ cases, {here} \\\\\\\\\\}"
];
inputs[]
| "\n",
.,
" " + expand[]- Output:
~/{Downloads,Pictures}/*.{jpg,gif,png}
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
It{{em,alic}iz,erat}e{d,}, please.
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
Julia
function getitem(s, depth=0)
out = [""]
while s != ""
c = s[1]
if depth > 0 && (c == ',' || c == '}')
return out, s
elseif c == '{'
x = getgroup(s[2:end], depth+1)
if x != ""
out, s = [a * b for a in out, b in x[1]], x[2]
continue
end
elseif c == '\\' && length(s) > 1
s, c = s[2:end], c * s[2]
end
out, s = [a * c for a in out], s[2:end]
end
return out, s
end
function getgroup(s, depth)
out, comma = "", false
while s != ""
g, s = getitem(s, depth)
if s == ""
break
end
out = vcat([out...], [g...])
if s[1] == '}'
if comma
return out, s[2:end]
end
return ["{" * a * "}" for a in out], s[2:end]
end
if s[1] == ','
comma, s = true, s[2:end]
end
end
return ""
end
const teststrings = [raw"~/{Downloads,Pictures}/*.{jpg,gif,png}",
raw"It{{em,alic}iz,erat}e{d,}, please.",
raw"{,{,gotta have{ ,\, again\, }}more }cowbell!",
raw"{}} some }{,{\\\\{ edge, edge} \,}{ cases, {here} \\\\\\\\\}'''"]
for s in teststrings
println("\n", s, "\n--------------------------------------------")
for ans in getitem(s)[1]
println(ans)
end
end
- Output:
~/{Downloads,Pictures}/*.{jpg,gif,png} -------------------------------------------- ~/Downloads/*.jpg ~/Pictures/*.jpg ~/Downloads/*.gif ~/Pictures/*.gif ~/Downloads/*.png ~/Pictures/*.png
It{{em,alic}iz,erat}e{d,}, please. -------------------------------------------- Itemized, please. Italicized, please. Iterated, please. Itemize, please. Italicize, please. Iterate, please.
{,{,gotta have{ ,\, again\, }}more }cowbell! -------------------------------------------- cowbell! more cowbell! gotta have more cowbell! gotta have\ again\ more cowbell!
{}} some }{,{\\\\{ edge, edge} \,}{ cases, {here} \\\\\\\\\}''' -------------------------------------------- {}} some }{,{\\\{ edge \}}{ cases, {here} \\\\\\\\\'''' {}} some }{,{\\\{ edge \}}{ cases, {here} \\\\\\\\\''''
Kotlin
// version 1.1.2
object BraceExpansion {
fun expand(s: String) = expandR("", s, "")
private val r = Regex("""([\\]{2}|[\\][,}{])""")
private fun expandR(pre: String, s: String, suf: String) {
val noEscape = s.replace(r, " ")
var sb = StringBuilder("")
var i1 = noEscape.indexOf('{')
var i2 = 0
outer@ while (i1 != -1) {
sb = StringBuilder(s)
var depth = 1
i2 = i1 + 1
while (i2 < s.length && depth > 0) {
val c = noEscape[i2]
if (c == '{') depth++
else if (c == '}') depth--
if (c == ',' && depth == 1) sb[i2] = '\u0000'
else if (c == '}' && depth == 0 && sb.indexOf("\u0000") != -1) break@outer
i2++
}
i1 = noEscape.indexOf('{', i1 + 1)
}
if (i1 == -1) {
if (suf.isNotEmpty()) expandR(pre + s, suf, "")
else println("$pre$s$suf")
} else {
for (m in sb.substring(i1 + 1, i2).split('\u0000')) {
expandR(pre + s.substring(0, i1), m, s.substring(i2 + 1) + suf)
}
}
}
}
fun main(args: Array<String>) {
val strings = arrayOf(
"""~/{Downloads,Pictures}/*.{jpg,gif,png}""",
"""It{{em,alic}iz,erat}e{d,}, please.""",
"""{,{,gotta have{ ,\, again\, }}more }cowbell!""",
"""{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}"""
)
for (s in strings) {
println()
BraceExpansion.expand(s)
}
}
- Output:
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
Lua
Note that this code isn't very memory efficient.
local function wrapEachItem(items, prefix, suffix)
local itemsWrapped = {}
for i, item in ipairs(items) do
itemsWrapped[i] = prefix .. item .. suffix
end
return itemsWrapped
end
local function getAllItemCombinationsConcatenated(aItems, bItems)
local combinations = {}
for _, a in ipairs(aItems) do
for _, b in ipairs(bItems) do
table.insert(combinations, a..b)
end
end
return combinations
end
local getItems -- Forward declaration.
local function getGroup(s, pos, depth)
local groupItems = {}
local foundComma = false
while pos <= #s do
local items
items, pos = getItems(s, pos, depth)
if pos > #s then break end
for _, item in ipairs(items) do
table.insert(groupItems, item)
end
local c = s:sub(pos, pos)
if c == "}" then -- Possibly end of group.
if foundComma then return groupItems, pos+1 end
return wrapEachItem(groupItems, "{", "}"), pos+1 -- No group.
elseif c == "," then
foundComma, pos = true, pos+1
end
end
return nil -- No group.
end
function getItems(s, pos, depth)
local items = {""}
while pos <= #s do
local c = s:sub(pos, pos)
if depth > 0 and (c == "," or c == "}") then -- End of item in surrounding group.
return items, pos
end
local groupItems, nextPos = nil
if c == "{" then -- Possibly start of a group.
groupItems, nextPos = getGroup(s, pos+1, depth+1)
end
if groupItems then
items, pos = getAllItemCombinationsConcatenated(items, groupItems), nextPos
else
if c == "\\" and pos < #s then -- Escaped character.
pos = pos + 1
c = c .. s:sub(pos, pos)
end
items, pos = wrapEachItem(items, "", c), pos+1
end
end
return items, pos
end
local tests = [[
~/{Downloads,Pictures}/*.{jpg,gif,png}
It{{em,alic}iz,erat}e{d,}, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
]]
for test in tests:gmatch"[^\n]+" do
print(test)
for _, item in ipairs(getItems(test, 1, 0)) do
print("\t"..item)
end
print()
end
- Output:
~/{Downloads,Pictures}/*.{jpg,gif,png}
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
...
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
Mathematica /Wolfram Language
(*The strategy is to first capture all special sub-expressions and reformat them so they are semantically clear. The built in function Distribute could then do the work of creating the alternatives, but the order wouldn't match that given in the instructions (although as a set the alternatives would be correct). I'll take a more complicated route so as to follow the instructions exactly.*)
(*A few named constants for readability.*)
EscapeToken="\\";(*In Mathematica, backslash is an escape character when inputing a string, so we need to escape it.*)
LeftBraceToken="{";
RightBraceToken="}";
(*This basically sequesters escaped substrings so that they don't get matched during later processing.*)
CaptureEscapes[exp:{___String}]:=SequenceReplace[exp,{EscapeToken,x_}:>EscapeToken<>x];
(*Any remaining braces are un-escaped. I'm "unstringifying" them to more easily pick them out during later processing.*)
CaptureBraces[exp:{___String}]:=ReplaceAll[exp,{LeftBraceToken->LeftBrace,RightBraceToken->RightBrace}];
(*Building up trees for the braced expressions. Extra braces are just raw data, so transform them back to strings.*)
CaptureBraceTrees[exp:{(_String|LeftBrace|RightBrace)...}]:=ReplaceAll[FixedPoint[SequenceReplace[{LeftBrace,seq:(_String|_BraceTree)...,RightBrace}:>BraceTree[seq]],exp],{LeftBrace->LeftBraceToken,RightBrace->RightBraceToken}];
(*At thie point, we should have an expression with well-braced substructures representing potential alternatives. We must expand brace trees to alternatives in the correct order.*)
ExpandBraceTrees[exp:Expr[head___String,bt_BraceTree,tail___]]:=ReplaceAll[Thread[Expr[head,ToAlternatives[bt],tail]],alt_Alt:>Sequence@@alt];
ExpandBraceTrees[exp:Expr[___String]]:={exp};
ExpandBraceTrees[exps:{__Expr}]:=Catenate[ExpandBraceTrees/@exps];
(*If there are no commas, then it's a literal sub-expression. Otherwise, it's a set of alternatives.*)
ToAlternatives[bt_BraceTree]:={LeftBraceToken<>StringJoin@@bt<>RightBraceToken}/;FreeQ[bt,","];
ToAlternatives[BraceTree[","]]=ToAlternatives[BraceTree["",",",""]];
ToAlternatives[bt:BraceTree[",",__]]:=ToAlternatives[Prepend[bt,""]];
ToAlternatives[bt:BraceTree[__,","]]:=ToAlternatives[Append[bt,""]];
ToAlternatives[bt_BraceTree]:=Alt@@@SequenceSplit[List@@bt,{","}];
NormalizeExpression=Apply[Expr]@*CaptureBraceTrees@*CaptureBraces@*CaptureEscapes@*Characters;
BraceExpand[str_String]:=ReplaceAll[FixedPoint[ExpandBraceTrees,NormalizeExpression[str]],Expr->StringJoin];
(*Data was stored in a local file.*)
BraceTestData=ReadList[FileNameJoin[{NotebookDirectory[],"BraceTestData.txt"}],String];BraceTestData//TableForm
~/{Downloads,Pictures}/*.{jpg,gif,png}
It{{em,alic}iz,erat}e{d,}, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
- Output:
Column[Column /@ BraceExpand /@ BraceTestData, Left, 2]
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,\\ edge \,{ cases, {here} \\\\\}
{}} some }{,\\ edge \,{ cases, {here} \\\\\}
Nim
proc expandBraces(str: string) =
var
escaped = false
depth = 0
bracePoints: seq[int]
bracesToParse: seq[int]
for idx, ch in str:
case ch
of '\\':
escaped = not escaped
of '{':
inc depth
if not escaped and depth == 1:
bracePoints = @[idx]
of ',':
if not escaped and depth == 1:
bracePoints &= idx
of '}':
if not escaped and depth == 1 and bracePoints.len >= 2:
bracesToParse = bracePoints & idx
dec depth
else:
discard
if ch != '\\':
escaped = false
if bracesToParse.len > 0:
let prefix = str[0..<bracesToParse[0]]
let suffix = str[(bracesToParse[^1] + 1)..^1]
for idx in 1..bracesToParse.high:
let option = str[(bracesToParse[idx - 1] + 1)..(bracesToParse[idx] - 1)]
expandBraces(prefix & option & suffix)
else:
echo " ", str
#———————————————————————————————————————————————————————————————————————————————————————————————————
when isMainModule:
for str in ["It{{em,alic}iz,erat}e{d,}, please.",
"~/{Downloads,Pictures}/*.{jpg,gif,png}",
"{,{,gotta have{ ,\\, again\\, }}more }cowbell!",
"{}} some }{,{\\\\{ edge, edge} \\,}{ cases, {here} \\\\\\\\\\}"]:
echo "\nExpansions of \"", str, "\":"
expandBraces(str)
- Output:
Expansions of "It{{em,alic}iz,erat}e{d,}, please.":
Itemized, please.
Italicized, please.
Iterated, please.
Itemize, please.
Italicize, please.
Iterate, please.
Expansions of "~/{Downloads,Pictures}/*.{jpg,gif,png}":
~/Downloads/*.jpg
~/Pictures/*.jpg
~/Downloads/*.gif
~/Pictures/*.gif
~/Downloads/*.png
~/Pictures/*.png
Expansions of "{,{,gotta have{ ,\, again\, }}more }cowbell!":
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
Expansions of "{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}":
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
Perl
Perl has a built-in glob function which does brace expansion, but it can't be used to solve this task because it also does shell-like word splitting, wildcard expansion, and tilde expansion at the same time.
The File::Glob core module gives access to the more low-level bsd_glob function which actually supports exclusive brace expansion, however it does not comply with this task's specification when it comes to preserving backslashes and handling unbalanced brace characters.
So here is a manual solution that implements the specification precisely:
sub brace_expand {
my $input = shift;
my @stack = ([my $current = ['']]);
while ($input =~ /\G ((?:[^\\{,}]++ | \\(?:.|\z))++ | . )/gx) {
if ($1 eq '{') {
push @stack, [$current = ['']];
}
elsif ($1 eq ',' && @stack > 1) {
push @{$stack[-1]}, ($current = ['']);
}
elsif ($1 eq '}' && @stack > 1) {
my $group = pop @stack;
$current = $stack[-1][-1];
# handle the case of brace pairs without commas:
@{$group->[0]} = map { "{$_}" } @{$group->[0]} if @$group == 1;
@$current = map {
my $c = $_;
map { map { $c . $_ } @$_ } @$group;
} @$current;
}
else { $_ .= $1 for @$current; }
}
# handle the case of missing closing braces:
while (@stack > 1) {
my $right = pop @{$stack[-1]};
my $sep;
if (@{$stack[-1]}) { $sep = ',' }
else { $sep = '{'; pop @stack }
$current = $stack[-1][-1];
@$current = map {
my $c = $_;
map { $c . $sep . $_ } @$right;
} @$current;
}
return @$current;
}
Usage demonstration:
while (my $input = <DATA>) {
chomp($input);
print "$input\n";
print " $_\n" for brace_expand($input);
print "\n";
}
__DATA__
~/{Downloads,Pictures}/*.{jpg,gif,png}
It{{em,alic}iz,erat}e{d,}, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
- Output:
~/{Downloads,Pictures}/*.{jpg,gif,png}
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
It{{em,alic}iz,erat}e{d,}, please.
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
Phix
Fairly straightforward recursive solution
-- demo\rosetta\Brace_expansion.exw with javascript_semantics function pair(sequence stems, sequence brest) sequence res = {} for i=1 to length(stems) do for j=1 to length(brest) do res = append(res,stems[i]&brest[j]) end for end for return res end function function brarse(string s) integer idx = 1 while idx<=length(s) do integer ch = s[idx] if ch='{' then sequence alts = {idx} idx += 1 integer l0 = idx bool nest = false, bl0 = false integer level = 1 while idx<=length(s) do switch s[idx] do case '{': level += 1 nest = true case '}': level -= 1 bl0 = (level=0) case ',': if level=1 then alts = append(alts,idx) end if case '\\': idx += 1 end switch if bl0 then exit end if idx += 1 end while if length(alts)>1 and level=0 then alts &= idx sequence stems = {} string stem = s[1..alts[1]-1] for i=2 to length(alts) do string rest = s[alts[i-1]+1..alts[i]-1] if nest then sequence inners = brarse(rest) for j=1 to length(inners) do stems = append(stems,stem&inners[j]) end for else stems = append(stems,stem&rest) end if end for return pair(stems,brarse(s[idx+1..$])) elsif nest then return pair({s[1..l0-1]},brarse(s[l0..$])) end if end if idx += 1 end while return {s} end function -- (since ? and pp() add their own backslash escapes:) procedure edump(sequence x) for i=1 to length(x) do printf(1,"%s\n",{x[i]}) end for end procedure edump(brarse("~/{Downloads,Pictures}/*.{jpg,gif,png}")) edump(brarse("It{{em,alic}iz,erat}e{d,}, please.")) edump(brarse(`{,{,gotta have{ ,\, again\, }}more }cowbell!`)) edump(brarse(`{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}`))
- Output:
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
PHP
function getitem($s,$depth=0) {
$out = [''];
while ($s) {
$c = $s[0];
if ($depth && ($c == ',' || $c == '}')) {
return [$out, $s];
}
if ($c == '{') {
$x = getgroup(substr($s, 1), $depth + 1);
if($x) {
$tmp = [];
foreach($out as $a) {
foreach($x[0] as $b) {
$tmp[] = $a . $b;
}
}
$out = $tmp;
$s = $x[1];
continue;
}
}
if ($c == '\\' && strlen($s) > 1) {
list($s, $c) = [substr($s, 1), ($c . $s[1])];
}
$tmp = [];
foreach($out as $a) {
$tmp[] = $a . $c;
}
$out = $tmp;
$s = substr($s, 1);
}
return [$out, $s];
}
function getgroup($s,$depth) {
list($out, $comma) = [[], false];
while ($s) {
list($g, $s) = getitem($s, $depth);
if (!$s) {
break;
}
$out = array_merge($out, $g);
if ($s[0] == '}') {
if ($comma) {
return [$out, substr($s, 1)];
}
$tmp = [];
foreach($out as $a) {
$tmp[] = '{' . $a . '}';
}
return [$tmp, substr($s, 1)];
}
if ($s[0] == ',') {
list($comma, $s) = [true, substr($s, 1)];
}
}
return null;
}
$lines = <<< 'END'
~/{Downloads,Pictures}/*.{jpg,gif,png}
It{{em,alic}iz,erat}e{d,}, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
END;
foreach( explode("\n", $lines) as $line ) {
printf("\n%s\n", $line);
foreach( getitem($line)[0] as $expansion ) {
printf(" %s\n", $expansion);
}
}
- Output:
~/{Downloads,Pictures}/*.{jpg,gif,png}
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
It{{em,alic}iz,erat}e{d,}, please.
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
PicoLisp
(de braceExpand (Str)
(let Lst
(make
(for (Lst (chop Str) Lst)
(case (pop 'Lst)
("\\" (link (pop 'Lst)))
("{"
(recur ()
(let L
(make
(while
(case (pop 'Lst)
("\\" (link (pop 'Lst)) Lst)
("{" (recurse) Lst)
("}" NIL)
("," (link 0) Lst) # Replace commata with '0'
(T (link @) Lst) ) ) )
(if (= "}" @) # Was closing brace
(if (member 0 L) # Has comma(ta)
(link (split L 0))
(chain (list "{") (replace L 0 ",") (list "}")))
(chain (list "{") (replace L 0 ",")) ) ) ) )
(T (link @)) ) ) )
(recur (Lst)
(ifn (find pair Lst)
(list (pack Lst))
(let R (recurse (cdr Lst))
(mapcan
'((A) (mapcar '((B) (pack A B)) R))
(if (pair (car Lst))
(mapcan recurse (car Lst))
(list (car Lst)) ) ) ) ) ) ) )Test:
(test
(quote
"~/Downloads/*.jpg"
"~/Downloads/*.gif"
"~/Downloads/*.png"
"~/Pictures/*.jpg"
"~/Pictures/*.gif"
"~/Pictures/*.png" )
(braceExpand "~/{Downloads,Pictures}/*.{jpg,gif,png}") )
(test
(quote
"Itemized, please."
"Itemize, please."
"Italicized, please."
"Italicize, please."
"Iterated, please."
"Iterate, please." )
(braceExpand "It{{em,alic}iz,erat}e{d,}, please.") )
(test
(quote
"cowbell!"
"more cowbell!"
"gotta have more cowbell!"
"gotta have\, again\, more cowbell!" )
(braceExpand "{,{,gotta have{ ,\\, again\\, }}more }cowbell!") )
(test
(quote
"{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}"
"{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}" )
(braceExpand "{}} some }{,{\\\\{ edge, edge} \\,}{ cases, {here} \\\\\\\\\\}") )PowerShell
function Expand-Braces ( [string]$String )
{
$Escaped = $False
$Stack = New-Object System.Collections.Stack
$ClosedBraces = $BracesToParse = $Null
ForEach ( $i in 0..($String.Length-1) )
{
Switch ( $String[$i] )
{
'\' {
$Escaped = -not $Escaped
break
}
'{' {
If ( -not $Escaped ) { $Stack.Push( [pscustomobject]@{ Delimiters = @( $i ) } ) }
}
',' {
If ( -not $Escaped -and $Stack.Count ) { $Stack.Peek().Delimiters += $i }
}
'}' {
If ( -not $Escaped -and $Stack.Count )
{
$Stack.Peek().Delimiters += $i
$ClosedBraces = $Stack.Pop()
If ( $ClosedBraces.Delimiters.Count -gt 2 )
{
$BracesToParse = $ClosedBraces
}
}
}
default { $Escaped = $False }
}
}
If ( $BracesToParse )
{
$Start = $String.Substring( 0, $BracesToParse.Delimiters[0] )
$End = $String.Substring( $BracesToParse.Delimiters[-1] + 1 )
ForEach ( $i in 0..($BracesToParse.Delimiters.Count-2) )
{
$Option = $String.Substring( $BracesToParse.Delimiters[$i] + 1, $BracesToParse.Delimiters[$i+1] - $BracesToParse.Delimiters[$i] - 1 )
Expand-Braces ( $Start + $Option + $End )
}
}
Else
{
$String
}
}
$TestStrings = @(
'It{{em,alic}iz,erat}e{d,}, please.'
'~/{Downloads,Pictures}/*.{jpg,gif,png}'
'{,{,gotta have{ ,\, again\, }}more }cowbell!'
'{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}'
)
ForEach ( $String in $TestStrings )
{
''
$String
'------'
Expand-Braces $String
}
- Output:
It{{em,alic}iz,erat}e{d,}, please.
------
Itemized, please.
Italicized, please.
Iterated, please.
Itemize, please.
Italicize, please.
Iterate, please.
~/{Downloads,Pictures}/*.{jpg,gif,png}
------
~/Downloads/*.jpg
~/Pictures/*.jpg
~/Downloads/*.gif
~/Pictures/*.gif
~/Downloads/*.png
~/Pictures/*.png
{,{,gotta have{ ,\, again\, }}more }cowbell!
------
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
------
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
Prolog
sym(',', commalist) --> ['\\',','], !.
sym(H, Context) --> [H], { not(H = '{'; H = '}'), (Context = commalist -> not(H = ','); true) }.
syms([H|T], Context) --> sym(H, Context), !, syms(T, Context).
syms([], _) --> [].
symbol(Symbol, Context) --> syms(Syms,Context), {atom_chars(Symbol, Syms)}.
braces(Member) --> ['{'], commalist(List), ['}'], {length(List, Len), Len > 1, member(Member, List)}.
commalist([H|T]) --> sym_braces(H, commalist), [','], commalist(T).
commalist([H]) --> sym_braces(H, commalist).
sym_braces(String, Context) --> symbol(S1, Context), braces(S2), sym_braces(S3, Context), {atomics_to_string([S1,S2,S3],String)}.
sym_braces(String, Context) --> braces(S1), symbol(S2, Context), sym_braces(S3, Context), {atomics_to_string([S1,S2,S3],String)}.
sym_braces(String, Context) --> symbol(String, Context).
sym_braces(String, _) --> braces(String).
sym_braces(String, Context) --> ['{'], sym_braces(S2, Context), {atomics_to_string(['{',S2],String)}.
sym_braces(String, Context) --> ['}'], sym_braces(S2, Context), {atomics_to_string(['}',S2],String)}.
grammar(String) --> sym_braces(String, braces).
brace_expansion(In, Out) :- atom_chars(In, Chars), findall(Out,grammar(Out, Chars, []), List), list_to_set(List, Out).
Testing:
?- brace_expansion("~/{Downloads,Pictures}/*.{jpg,gif,png}", Out).
Out = ["~/Downloads/*.jpg","~/Downloads/*.gif","~/Downloads/*.png","~/Pictures/*.jpg","~/Pictures/*.gif","~/Pictures/*.png"].
?- brace_expansion("It{{em,alic}iz,erat}e{d,}, please.", Out).
Out = ["Itemized, please.", "Itemize, please.", "Iterated, please.", "Iterate, please.", "Italicized, please.", "Italicize, please."].
?- brace_expansion("{,{,gotta have{ ,\\, again\\, }}more }cowbell!", Out).
Out = ["cowbell!", "more cowbell!", "gotta have more cowbell!", "gotta have, again, more cowbell!"].
Python
def getitem(s, depth=0):
out = [""]
while s:
c = s[0]
if depth and (c == ',' or c == '}'):
return out,s
if c == '{':
x = getgroup(s[1:], depth+1)
if x:
out,s = [a+b for a in out for b in x[0]], x[1]
continue
if c == '\\' and len(s) > 1:
s, c = s[1:], c + s[1]
out, s = [a+c for a in out], s[1:]
return out,s
def getgroup(s, depth):
out, comma = [], False
while s:
g,s = getitem(s, depth)
if not s: break
out += g
if s[0] == '}':
if comma: return out, s[1:]
return ['{' + a + '}' for a in out], s[1:]
if s[0] == ',':
comma,s = True, s[1:]
return None
# stolen cowbells from Raku example
for s in '''~/{Downloads,Pictures}/*.{jpg,gif,png}
It{{em,alic}iz,erat}e{d,}, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
{}} some }{,{\\\\{ edge, edge} \,}{ cases, {here} \\\\\\\\\}'''.split('\n'):
print "\n\t".join([s] + getitem(s)[0]) + "\n"
- Output:
~/{Downloads,Pictures}/*.{jpg,gif,png}
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
It{{em,alic}iz,erat}e{d,}, please.
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
Racket
#lang racket/base
(require racket/match)
(define (merge-lists as . bss)
(match bss
['() as]
[(cons b bt)
(apply merge-lists
(for*/list ((a (in-list as)) (b (in-list b))) (append a b))
bt)]))
(define (get-item cs depth)
(let loop ((out '(())) (cs cs))
(match cs
['() (values out cs)]
[`(,(or #\, #\}) . ,more) #:when (positive? depth) (values out cs)]
[`(#\{ . ,more)
(=> no-group-match)
(define-values (group-out group-rem) (get-group more (add1 depth) no-group-match))
(loop (merge-lists out group-out) group-rem)]
[(or `(#\\ ,c ,more ...) `(,c . ,more)) (loop (merge-lists out (list (list c))) more)])))
(define (get-group cs depth no-group-match)
(let loop ((out '()) (cs cs) (comma? #f))
(when (null? cs) (no-group-match))
(define-values (item-out item-rem) (get-item cs depth))
(when (null? item-rem) (no-group-match))
(let ((out (append out item-out)))
(match item-rem
[`(#\} . ,more) #:when comma? (values out more)]
[`(#\} . ,more) (values (merge-lists '((#\{)) out '((#\}))) more)]
[`(#\, . ,more) (loop out more #t)]
[_ (no-group-match)]))))
(define (brace-expand s)
(let-values (([out rem] (get-item (string->list s) 0))) (map list->string out)))
(module+ test
(define patterns
(list
"~/{Downloads,Pictures}/*.{jpg,gif,png}"
"It{{em,alic}iz,erat}e{d,}, please."
#<<P
{,{,gotta have{ ,\, again\, }}more }cowbell!
P
#<<P
{}} some }{,{\\\\{ edge, edge} \,}{ cases, {here} \\\\\\\\\}
P
))
(for ((s (in-list patterns)) #:when (printf "expand: ~a~%" s) (x (in-list (brace-expand s))))
(printf "\t~a~%" x)))
- Output:
expand: ~/{Downloads,Pictures}/*.{jpg,gif,png}
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
expand: It{{em,alic}iz,erat}e{d,}, please.
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
expand: {,{,gotta have{ ,\, again\, }}more }cowbell!
cowbell!
more cowbell!
gotta have more cowbell!
gotta have, again, more cowbell!
expand: {}} some }{,{\\\\{ edge, edge} \,}{ cases, {here} \\\\\\\\\}
{}} some }{,{\\ edge ,}{ cases, {here} \\\\}
{}} some }{,{\\ edge ,}{ cases, {here} \\\\}
Raku
(formerly Perl 6) The task description allows the taking of shortcuts, but please note that we are not taking any shortcuts here. The solution is short because this particular problem happens to map quite naturally to the strengths of Raku.
First, the parsing is handled with a grammar that can backtrack in the few places this problem needs it. The + quantifier matches one or more alternatives (we handle the case of a single alternative in the walk now), and the % modifier requires a comma between each quantified item to its left. Note that the * quantifiers do not backtrack here, because the token keyword suppresses that; all the backtracking here fails over to a different alternative in an outer alternation (that is, things separated by the | character in the grammar. Most of these failovers just nibble an uninteresting character and continue.)
On the other end, we recursively walk the parse tree returning expanded sublists, and we do the cartesian concatenation of sublists at each level by use of the X~ operator, which is a "cross" metaoperator used on a simple ~ concatenation. As a list infix operator, X~ does not care how many items are on either side, which is just what you want in this case, since some of the arguments are strings and some are lists. Here we use a fold or reduction form in square brackets to interpose the cross-concat between each value generated by the map, which returns a mixture of lists and literal strings. One other thing that might not be obvious: if we bind to the match variable, $/, we automatically get all the syntactic sugar for its submatches. In this case, $0 is short for $/[0], and represents all the submatches captured by 0th set of parens in either TOP or alt. $<meta> is likewise short for $/<meta>, and retrieves what was captured by that named submatch.
grammar BraceExpansion {
token TOP { ( <meta> | . )* }
token meta { '{' <alts> '}' | \\ . }
token alts { <alt>+ % ',' }
token alt { ( <meta> | <-[ , } ]> )* }
}
sub crosswalk($/) {
|[X~] flat '', $0.map: -> $/ { $<meta><alts><alt>.&alternatives or ~$/ }
}
sub alternatives($_) {
when :not { () }
when 1 { '{' X~ $_».&crosswalk X~ '}' }
default { $_».&crosswalk }
}
sub brace-expand($s) { crosswalk BraceExpansion.parse($s) }
# Testing:
sub bxtest(*@s) {
for @s -> $s {
say "\n$s";
for brace-expand($s) {
say " ", $_;
}
}
}
bxtest Q:to/END/.lines;
~/{Downloads,Pictures}/*.{jpg,gif,png}
It{{em,alic}iz,erat}e{d,}, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
a{b{1,2}c
a{1,2}b}c
a{1,{2},3}b
more{ darn{ cowbell,},}
ab{c,d\,e{f,g\h},i\,j{k,l\,m}n,o\,p}qr
{a,{\,b}c
a{b,{{c}}
{a{\}b,c}d
END
- Output:
~/{Downloads,Pictures}/*.{jpg,gif,png}
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
It{{em,alic}iz,erat}e{d,}, please.
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some {\\{edge,edgy} }{ cases, here\\\}
{}} some {\\edge }{ cases, here\\\}
{}} some {\\edgy }{ cases, here\\\}
a{b{1,2}c
a{b1c
a{b2c
a{1,2}b}c
a1b}c
a2b}c
a{1,{2},3}b
a1b
a{2}b
a3b
more{ darn{ cowbell,},}
more darn cowbell
more darn
more
ab{c,d\,e{f,g\h},i\,j{k,l\,m}n,o\,p}qr
abcqr
abd\,efqr
abd\,eg\hqr
abi\,jknqr
abi\,jl\,mnqr
abo\,pqr
{a,{\,b}c
{a,{\,b}c
a{b,{{c}}
a{b,{{c}}
{a{\}b,c}d
{a\}bd
{acd
REXX
/*- REXX --------------------------------------------------------------
* Brace expansion
* 26.07.2016
* s.* holds the set of strings
*--------------------------------------------------------------------*/
text.1='{,{,gotta have{ ,\, again\, }}more }cowbell!'
text.2='~/{Downloads,Pictures}/*.{jpg,gif,png}'
text.3='It{{em,alic}iz,erat}e{d,}, please. '
text.4='{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\} '
text.5='x{,a,b,c}{d,e}y'
text.6='aa{,{,11}cc}22'
text.7='{}'
Parse Arg dbg
oid='brace.xxx'; 'erase' oid
Do case=1 To 7
Call brac text.case
End
Return
brac:
s.=0
Parse Arg s
Say ''
Say ' 's
s.1.0=1 /* first iteration */
s.1.1=s /* the initial string */
Do it=1 To 10 Until todo=0 /* Iterate until all done */
todo=0 /* will be 1 if more to be done */
Call dbg 'Iteration' it
do di=1 To s.it.0 /* show current state */
Call dbg 's.'it'.'di s.it.di
End
ita=it+1 /* index for next set of strings*/
xp=0
do di=1 To s.it.0 /* loop over all strings */
Call dbg it'.'di s.it.di
Call bra s.it.di /* analyze current string */
If braces=1 Then Do /* If brace groups were found */
Do bgi=1 To bgdata.0 /* loop over grace groups */
If end.bgi=0 Then Iterate /* Incomplete bg (... ) */
clist=''
Do cj=1 To ci.bgi.0
clist=clist ci.bgi.cj
End
Call dbg bgdata.bgi '->' clist
If ccount.bgi>0 Then Do /* comma(s) founf in bg */
Call expand bgi /* expand this bg */
xp=1 /* indicate that we worked */
Leave
End
End
If xp=0 Then Do /* nothing done */
z=s.ita.0+1 /* copy string to next iteration*/
s.ita.z=s.it.di
End
End
Else Do /* no brace group */
z=s.ita.0+1 /* copy string to next iteration*/
s.ita.z=s
s.ita.0=z
End
End
Do dd=1 To s.ita.0 /* log current set of strings */
Call dbg ita dd s.ita.dd
End
End
Do dd=1 To s.it.0 /* show final set of strings */
Say dd s.it.dd
End
Return
bra:
/*---------------------------------------------------------------------
* Analyze the given string
* Input: s
* Output:
* bgdata.* Array of data about brace groups:
* level start column comma positions end column
*--------------------------------------------------------------------*/
parse Arg s
Call dbg 'bra:' s
level=0
bgdata.=0
bgn=0
bgnmax=0
ccount.=0
ol=''
ci.=0
bgnl=''
braces=0
end.=0
escape=0
Do i=1 To length(s)
c=substr(s,i,1)
Select
When escape Then
escape=0
When c='\' Then
escape=1
When c='{' Then Do
level=level+1
Call bm c
co=level
End
When c='}' Then Do
If level>0 Then Do
co=level
Call bm c
level=level-1
End
End
When c=',' Then Do
co=level
If co>0 Then Do
ccount.bgn=ccount.bgn+1
z=ccount.bgn
ci.bgn.0=z
ci.bgn.z=i
End
If ccount.bgn>0 Then
braces=1
End
Otherwise
co=level
End
ol=ol||co
bgnl=bgnl||bgn
End
Call dbg s
Call dbg ol
Call dbg left(copies('123456789.',10),length(s))
Call dbg bgnl
Do bgi=1 To bgdata.0
If end.bgi=1 Then Do
cl=''
Do cii=1 To ci.bgi.0
cl=cl ci.bgi.cii
End
Parse Var bgdata.bgi level a e
Call dbg bgi level a cl e
End
End
Return
bm:
/*---------------------------------------------------------------------
* Brace Management
* for '{' create a new brace group )record level and start column
* for '}' look for corresponding bg and add end column
* Input: column and character ( '{' or '}' )
* Output: bgdata.* level start-column [end-column]
*--------------------------------------------------------------------*/
Parse Arg oc
Call dbg oc i level
If oc='{' Then Do
z=bgdata.0+1
bgdata.z=level i
bgdata.0=z
bgn=bgnmax+1
bgnmax=bgn
End
Else Do
Do bgi=bgdata.0 To 1 By -1
If level=word(bgdata.bgi,1) Then Do
bgdata.bgi=bgdata.bgi i
end.bgi=1
Leave
End
End
bgn=bgn-1
Call dbg bgdata.bgi 'bgn='bgn
End
Return
expand:
/*---------------------------------------------------------------------
* Expand a brace group in string s
*--------------------------------------------------------------------*/
Parse Arg bgi
Parse Var bgdata.bgi . start end
clist=start clist end
If words(clist)>0 Then Do /* commas in brace group */
left=left(s,start-1) /* part of s before the '{' */
rite=substr(s,end+1) /* part of s after the '}' */
Do k=1 To words(clist)-1 /* Loop over comma positions */
a=word(clist,k) /* start position */
e=word(clist,k+1) /* end position */
choice.k=substr(s,a+1,e-a-1) /* one of the choices */
z=s.ita.0+1 /* add new string to next set */
s.ita.z=left||choice.k||rite /* construct new string */
s.ita.0=z
todo=1 /* maybe more to be done */
End
End
Else Do /* no commas */
z=s.ita.0+1 /* copy string as is to next set*/
s.ita.z=s
s.ita.0=z
End
Do zz=1 To s.ita.0
Call dbg zz s.ita.zz
End
Return
dbg: /* handle debug output */
If dbg<>'' Then /* argument given */
Say arg(1) /* show on screen */
Call lineout oid,arg(1) /* write to file */
Return
- Output:
J:\>rexx braces
{,{,gotta have{ ,\, again\, }}more }cowbell!
1 cowbell!
2 more cowbell!
3 gotta have more cowbell!
4 gotta have\, again\, more cowbell!
~/{Downloads,Pictures}/*.{jpg,gif,png}
1 ~/Downloads/*.jpg
2 ~/Downloads/*.gif
3 ~/Downloads/*.png
4 ~/Pictures/*.jpg
5 ~/Pictures/*.gif
6 ~/Pictures/*.png
It{{em,alic}iz,erat}e{d,}, please.
1 Itemized, please.
2 Itemize, please.
3 Italicized, please.
4 Italicize, please.
5 Iterated, please.
6 Iterate, please.
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
1 {}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
2 {}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
x{,a,b,c}{d,e}y
1 xdy
2 xey
3 xady
4 xaey
5 xbdy
6 xbey
7 xcdy
8 xcey
aa{,{,11}cc}22
1 aa22
2 aacc22
3 aa11cc22
{}
1 {}
Ruby
def getitem(s, depth=0)
out = [""]
until s.empty?
c = s[0]
break if depth>0 and (c == ',' or c == '}')
if c == '{' and x = getgroup(s[1..-1], depth+1)
out = out.product(x[0]).map{|a,b| a+b}
s = x[1]
else
s, c = s[1..-1], c + s[1] if c == '\\' and s.size > 1
out, s = out.map{|a| a+c}, s[1..-1]
end
end
return out, s
end
def getgroup(s, depth)
out, comma = [], false
until s.empty?
g, s = getitem(s, depth)
break if s.empty?
out += g
case s[0]
when '}' then return (comma ? out : out.map{|a| "{#{a}}"}), s[1..-1]
when ',' then comma, s = true, s[1..-1]
end
end
end
strs = <<'EOS'
~/{Downloads,Pictures}/*.{jpg,gif,png}
It{{em,alic}iz,erat}e{d,}, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
EOS
strs.each_line do |s|
puts s.chomp!
puts getitem(s)[0].map{|str| "\t"+str}
puts
end
- Output:
~/{Downloads,Pictures}/*.{jpg,gif,png}
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
It{{em,alic}iz,erat}e{d,}, please.
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
Rust
const OPEN_CHAR: char = '{';
const CLOSE_CHAR: char = '}';
const SEPARATOR: char = ',';
const ESCAPE: char = '\\';
#[derive(Debug, PartialEq, Clone)]
enum Token {
Open,
Close,
Separator,
Payload(String),
Branches(Branches),
}
impl From<char> for Token {
fn from(ch: char) -> Token {
match ch {
OPEN_CHAR => Token::Open,
CLOSE_CHAR => Token::Close,
SEPARATOR => Token::Separator,
_ => panic!("Non tokenizable char!"),
}
}
}
#[derive(Debug, PartialEq, Clone)]
struct Branches {
tokens: Vec<Vec<Token>>,
}
impl Branches {
fn new() -> Branches {
Branches{
tokens: Vec::new(),
}
}
fn add_branch(&mut self, branch: Vec<Token>) {
self.tokens.push(branch);
}
fn from(tokens: &Vec<Token>) -> Branches {
let mut branches = Branches::new();
let mut tail = tokens.clone();
while let Some(pos) = tail.iter().position(|token| { *token == Token::Separator }) {
let mut rest = tail.split_off(pos);
branches.add_branch(tail);
rest.remove(0);
tail = rest;
}
branches.add_branch(tail);
branches
}
}
impl From<Branches> for Token {
fn from(branches: Branches) -> Token {
Token::Branches(branches)
}
}
impl From<Vec<Token>> for Branches {
fn from(tokens: Vec<Token>) -> Branches {
Branches::from(&tokens)
}
}
impl From<Token> for String {
fn from(token: Token) -> String {
match token {
Token::Branches(_) => panic!("Cannot convert to String!"),
Token::Payload(text) => text,
Token::Open => OPEN_CHAR.to_string(),
Token::Close => CLOSE_CHAR.to_string(),
Token::Separator => SEPARATOR.to_string(),
}
}
}
impl From<Branches> for Vec<String> {
fn from(branches: Branches) -> Vec<String> {
let Branches{ tokens: token_lines } = branches;
let mut vec: Vec<String> = Vec::new();
let braces = { if token_lines.len() == 1 { true } else { false } };
for tokens in token_lines {
let mut vec_string = output(tokens);
vec.append(&mut vec_string);
}
if braces {
vec.iter()
.map(|line| {
format!("{}{}{}", OPEN_CHAR, line, CLOSE_CHAR)
}).
collect::<Vec<String>>()
} else {
vec
}
}
}
impl From<Token> for Vec<String> {
fn from(token: Token) -> Vec<String> {
match token {
Token::Branches(branches) => {
branches.into()
},
_ => {
let frag: String = token.into();
vec![frag]
},
}
}
}
fn tokenize(string: &str) -> Vec<Token> {
let mut tokens: Vec<Token> = Vec::new();
let mut chars = string.chars();
let mut payload = String::new();
while let Some(ch) = chars.next() {
match ch {
OPEN_CHAR | SEPARATOR | CLOSE_CHAR => {
if payload.len() > 0 {
tokens.push(Token::Payload(payload));
}
payload = String::new();
if ch == CLOSE_CHAR {
let pos = tokens.iter().rposition(|token| *token == Token::Open);
if let Some(pos) = pos {
let branches: Branches = {
let mut to_branches = tokens.split_off(pos);
to_branches.remove(0);
to_branches
}.into();
tokens.push(branches.into());
} else {
tokens.push(ch.into());
}
} else {
tokens.push(ch.into());
}
},
ESCAPE => {
payload.push(ch);
if let Some(next_char) = chars.next() {
payload.push(next_char);
}
},
_ => payload.push(ch),
}
}
let payload = payload.trim_end();
if payload.len() > 0 {
tokens.push(Token::Payload(payload.into()));
}
tokens
}
fn output(tokens: Vec<Token>) -> Vec<String> {
let mut output: Vec<String> = vec![String::new()];
for token in tokens {
let mut aux: Vec<String> = Vec::new();
let strings: Vec<String> = token.into();
for root in &output {
for string in &strings {
aux.push({format!("{}{}", root, string)});
}
}
output = aux;
}
output
}
fn main() {
let mut input: String = String::new();
std::io::stdin().read_line(&mut input).unwrap();
let tokens: Vec<Token> = tokenize(&input);
// println!("Tokens:\n{:#?}", tokens);
let output = output(tokens);
for line in &output {
println!("{}", line);
}
}
- Output:
INPUT -> ~/{Downloads,Pictures}/*.{jpg,gif,png}
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
INPUT -> It{{em,alic}iz,erat}e{d,}, please.
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
INPUT -> {,{,gotta have{ ,\, again\, }}more }cowbell!
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
INPUT -> {}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
fn main() {
let input = "~/{Downloads,Pictures}/*.{jpg,gif,png}
It{{em,alic}iz,erat}e{d,}, please.
{,{,gotta have{ ,\\, again\\, }}more }cowbell!
{}} some }{,{\\\\{ edge, edge} \\,}{ cases, {here} \\\\\\\\\\}";
for line in input.split("\n") {
println!("{}", line);
for line in get_item(line, 0).0 {
println!("\t{}", line);
}
}
}
fn get_item(s: &str, depth: usize) -> (Vec<String>, &str) {
let mut out = vec![String::new()];
let mut s = s;
while !s.is_empty() {
let mut c = s.chars().nth(0).unwrap().to_string();
if depth > 0 && (c == "," || c == "}") {
return (out, s);
}
if c == "{" {
let x = get_group(&s[1..], depth + 1);
if x.is_some() {
let (items, s_new) = x.unwrap();
out = out
.iter()
.map(|out_item| {
items
.iter()
.map(|item| format!("{}{}", out_item, item))
.collect::<Vec<String>>()
})
.flatten()
.collect();
s = s_new;
continue;
}
}
if c == "\\" && s.len() > 1 {
s = &s[1..];
c.push(s.chars().nth(0).unwrap());
}
out = out
.iter()
.map(|o| [o, &c[..]].concat())
.collect::<Vec<String>>();
s = &s[1..];
}
(out, s)
}
fn get_group(s: &str, depth: usize) -> Option<(Vec<String>, &str)> {
let mut out: Vec<String> = vec![];
let mut comma = false;
let mut s = s;
while !s.is_empty() {
let (g, new_s) = get_item(s, depth);
s = new_s;
if s.is_empty() {
break;
}
out.extend(g);
if s.chars().nth(0).unwrap() == '}' {
if comma {
return Some((out, &s[1..]));
}
return Some((
out.iter().map(|item| format!("{{{}}}", item)).collect(),
&s[1..],
));
}
if s.chars().nth(0).unwrap() == ',' {
comma = true;
s = &s[1..];
}
}
None
}
- Output:
~/{Downloads,Pictures}/*.{jpg,gif,png}
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
It{{em,alic}iz,erat}e{d,}, please.
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
Scala
import collection.mutable.ListBuffer
case class State(isChild: Boolean, alts: ListBuffer[String], rem: List[Char])
def expand(s: String): Seq[String] = {
def parseGroup(s: State): State = s.rem match {
case Nil => s.copy(alts = ListBuffer("{" + s.alts.mkString(",")))
case ('{' | ',')::sp =>
val newS = State(true, ListBuffer(""), rem = sp)
val elem = parseElem(newS)
elem.rem match {
case Nil => elem.copy(alts = elem.alts.map(a => "{" + s.alts.map(_ + ",").mkString("") + a))
case elemrem => parseGroup(s.copy(alts = (s.alts ++= elem.alts), rem = elem.rem))
}
case '}'::sp =>
if (s.alts.isEmpty) s.copy(alts = ListBuffer("{}"), rem = sp)
else if(s.alts.length == 1) s.copy(alts = ListBuffer("{"+s.alts.head + "}"), rem = sp)
else s.copy(rem = sp)
case _ => throw new Exception("parseGroup should be called only with delimitors")
}
def parseElem(s: State): State = s.rem match {
case Nil => s
case '{'::sp =>
val ys = parseGroup(State(true, ListBuffer(), s.rem))
val newAlts = for { x <- s.alts; y <- ys.alts} yield x + y
parseElem(s.copy(alts = newAlts, rem = ys.rem))
case (',' | '}')::_ if s.isChild => s
case '\\'::c::sp => parseElem(s.copy(alts = s.alts.map(_ + '\\' + c), rem = sp))
case c::sp => parseElem(s.copy(alts = s.alts.map(_ + c), rem = sp))
}
parseElem(State(false, ListBuffer(""), s.toList)).alts
}
Demonstrating:
println(expand("""~/{Downloads,Pictures}/*.{jpg,gif,png}""") mkString "\n")
println(expand("It{{em,alic}iz,erat}e{d,}, please.") mkString "\n")
println(expand("""{,{,gotta have{ ,\, again\, }}more }cowbell!""") mkString "\n")
println(expand("""{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}""") mkString "\n")
- Output:
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,\\ edge \,{ cases, {here} \\\\\}
{}} some }{,\\ edge \,{ cases, {here} \\\\\}
Scheme
(define (parse-brackets str)
;; We parse the bracketed strings using an accumulator and a stack
;;
;; lst is the stream of tokens
;; acc is the accumulated list of "bits" in this branch
;; stk is a list of partially completed accumulators
;;
(let go ((lst (string->list str))
(acc '())
(stk '()))
(cond ((null? lst)
(unless (null? stk)
(error "parse-brackets" 'non-empty-stack))
(comma-sep acc))
((eq? (car lst) #\{)
(go (cdr lst)
'()
(cons acc stk)))
((eq? (car lst) #\})
(when (null? stk)
(error "parse-brackets" 'empty-stack))
(go (cdr lst)
(cons (comma-sep acc) (car stk))
(cdr stk)))
(else
(go (cdr lst)
(cons (car lst) acc)
stk)))))
(define (comma-sep lst)
;; This function is applied to the accumulator, it does three things:
;; - it reverses the list
;; - joins characters into short strings
;; - splits the strings based on commas
;;
(let go ((lst lst)
(acc '())
(rst '()))
(if (null? lst)
(cons (list->string acc) rst)
(cond ((eq? #\, (car lst))
(go (cdr lst)
'()
(cons (list->string acc) rst)))
((char? (car lst))
(go (cdr lst)
(cons (car lst) acc)
rst))
(else
(go (cdr lst)
'()
(cons (car lst)
(cons (list->string acc)
rst))))))))
;; We use the list monad for the nondeterminism needed to expand out every possible bracket option
(define (concatenate lists)
(apply append lists))
(define (return x)
(list x))
(define (>>= l f)
(concatenate (map f l)))
(define (sequence lsts)
(if (null? lsts)
(return '())
(>>= (car lsts)
(lambda (option)
(>>= (sequence (cdr lsts))
(lambda (tail)
(return (cons option tail))))))))
(define (expand-inner tree)
(if (string? tree)
(return tree)
(>>= tree
(lambda (option)
(expand-inner option)))))
(define (expand tree)
(define (string-append* lst) (apply string-append lst))
(map string-append* (sequence (map expand-inner tree))))
(define (bracket-expand str)
(expand (parse-brackets str)))
(bracket-expand "It{{em,alic}iz,erat}e{d,}")
;; '("Ited" "Ite" "Itemed" "Iteme" "Italiced" "Italice" "Itized" "Itize" "Iterated" "Iterate")
Seed7
$ include "seed7_05.s7i";
const proc: expandBraces (in string: stri) is func
local
var boolean: escaped is FALSE;
var integer: depth is 0;
var array integer: bracePoints is 0 times 0;
var array integer: bracesToParse is 0 times 0;
var string: prefix is "";
var string: suffix is "";
var string: option is "";
var integer: idx is 0;
begin
for key idx range stri do
case stri[idx] of
when {'\\'}:
escaped := not escaped;
when {'{'}:
incr(depth);
if not escaped and depth = 1 then
bracePoints := [] (idx);
end if;
when {','}:
if not escaped and depth = 1 then
bracePoints &:= idx;
end if;
when {'}'}:
if not escaped and depth = 1 and length(bracePoints) >= 2 then
bracesToParse := bracePoints & [] (idx);
end if;
decr(depth);
end case;
if stri[idx] <> '\\' then
escaped := FALSE;
end if;
end for;
if length(bracesToParse) <> 0 then
prefix := stri[.. pred(bracesToParse[1])];
suffix := stri[succ(bracesToParse[length(bracesToParse)]) ..];
for idx range 1 to pred(length(bracesToParse)) do
option := stri[succ(bracesToParse[idx]) .. pred(bracesToParse[succ(idx)])];
expandBraces(prefix & option & suffix);
end for;
else
writeln(stri);
end if;
end func;
const proc: main is func
local
var string: stri is "";
begin
for stri range [] ("It{{em,alic}iz,erat}e{d,}, please.",
"~/{Downloads,Pictures}/*.{jpg,gif,png}",
"{,{,gotta have{ ,\\, again\\, }}more }cowbell!",
"{}} some }{,{\\\\{ edge, edge} \\,}{ cases, {here} \\\\\\\\\\}") do
writeln;
expandBraces(stri);
end for;
end func;- Output:
Itemized, please.
Italicized, please.
Iterated, please.
Itemize, please.
Italicize, please.
Iterate, please.
~/Downloads/*.jpg
~/Pictures/*.jpg
~/Downloads/*.gif
~/Pictures/*.gif
~/Downloads/*.png
~/Pictures/*.png
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
Sidef
func brace_expand (input) {
var current = ['']
var stack = [[current]]
loop {
var t = input.match(
/\G ((?:[^\\{,}]++ | \\(?:.|\z))++ | . )/gx
)[0] \\ break
if (t == '{') {
stack << [current = ['']]
}
elsif ((t == ',') && (stack.len > 1)) {
stack[-1] << (current = [''])
}
elsif ((t == '}') && (stack.len > 1)) {
var group = stack.pop
current = stack[-1][-1]
# handle the case of brace pairs without commas:
group[0][] = group[0].map{ '{'+_+'}' }... if (group.len == 1)
current[] = current.map { |c|
group.map { .map { c + _ }... }...
}...
}
else {
current[] = current.map { _ + t }...
}
}
# handle the case of missing closing braces:
while (stack.len > 1) {
var right = stack[-1].pop
var sep = ','
if (stack[-1].is_empty) {
sep = '{'
stack.pop
}
current = stack[-1][-1]
current[] = current.map { |c|
right.map { c + sep + _ }...
}...
}
return current
}
DATA.each { |line|
say line
brace_expand(line).each { "\t#{_}".say }
say ''
}
__DATA__
~/{Downloads,Pictures}/*.{jpg,gif,png}
It{{em,alic}iz,erat}e{d,}, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
- Output:
~/{Downloads,Pictures}/*.{jpg,gif,png}
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
It{{em,alic}iz,erat}e{d,}, please.
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
Simula
CLASS ARRAYLISTS;
BEGIN
CLASS ITEM;;
CLASS ITEMARRAY(N); INTEGER N;
BEGIN
REF(ITEM) ARRAY DATA(1:N);
! OUTTEXT("NEW ITEMARRAY WITH ");!OUTINT(N, 0);!OUTTEXT(" ELEMENTS");
! OUTIMAGE;
END;
CLASS ARRAYLIST;
BEGIN
PROCEDURE EXPAND(N); INTEGER N;
BEGIN
INTEGER I;
REF(ITEMARRAY) TEMP;
! OUTTEXT("EXPAND TO CAPACITY ");!OUTINT(N, 0);!OUTIMAGE;
TEMP :- NEW ITEMARRAY(N);
FOR I := 1 STEP 1 UNTIL SIZE DO
TEMP.DATA(I) :- ITEMS.DATA(I);
ITEMS :- TEMP;
END;
PROCEDURE ADD(T); REF(ITEM) T;
BEGIN
IF SIZE + 1 > CAPACITY THEN
BEGIN
CAPACITY := 2 * CAPACITY;
EXPAND(CAPACITY);
END;
SIZE := SIZE + 1;
ITEMS.DATA(SIZE) :- T;
! OUTTEXT("SIZE IS ");!OUTINT(SIZE, 0);!OUTIMAGE;
END;
PROCEDURE REMOVE(I); INTEGER I;
BEGIN
INTEGER J;
IF I < 1 OR I > SIZE THEN ERROR("REMOVE: INDEX OUT OF BOUNDS");
FOR J := I STEP 1 UNTIL SIZE - 1 DO
ITEMS.DATA(J) :- ITEMS.DATA(J + 1);
ITEMS.DATA(SIZE) :- NONE;
SIZE := SIZE - 1;
END;
REF(ITEM) PROCEDURE GET(I); INTEGER I;
BEGIN
IF I < 1 OR I > SIZE THEN ERROR("GET: INDEX OUT OF BOUNDS");
GET :- ITEMS.DATA(I);
END;
INTEGER CAPACITY;
INTEGER SIZE;
REF(ITEMARRAY) ITEMS;
CAPACITY := 20;
SIZE := 0;
EXPAND(CAPACITY);
END;
ITEM CLASS TEXTITEM(TXT); TEXT TXT;;
ARRAYLIST CLASS TEXTARRAYLIST;
BEGIN
PROCEDURE ADD(T); TEXT T;
THIS TEXTARRAYLIST QUA ARRAYLIST.ADD(NEW TEXTITEM(T));
TEXT PROCEDURE GET(I); INTEGER I;
GET :- THIS TEXTARRAYLIST QUA ARRAYLIST.GET(I) QUA TEXTITEM.TXT;
END;
ITEM CLASS REALITEM(X); REAL X;;
ARRAYLIST CLASS REALARRAYLIST;
BEGIN
PROCEDURE ADD(X); REAL X;
THIS REALARRAYLIST QUA ARRAYLIST.ADD(NEW REALITEM(X));
REAL PROCEDURE GET(I); INTEGER I;
GET := THIS REALARRAYLIST QUA ARRAYLIST.GET(I) QUA REALITEM.X;
END;
END;EXTERNAL CLASS ARRAYLISTS;
ARRAYLISTS
BEGIN
CLASS TUPLE(TLIST,T);
REF(TEXTARRAYLIST) TLIST;
TEXT T;
BEGIN
END TUPLE;
REF(TUPLE) PROCEDURE GETITEM(S, DEPTH);
TEXT S;
INTEGER DEPTH;
BEGIN
REF(TUPLE) RESULT;
REF(TEXTARRAYLIST) OUT;
OUT :- NEW TEXTARRAYLIST;
OUT.ADD("");
CONTINUE:
WHILE S.LENGTH > 0 DO BEGIN
CHARACTER C;
TEXT CTEXT;
S.SETPOS(1); C := S.GETCHAR; CTEXT :- BLANKS(1); CTEXT.PUTCHAR(C);
IF DEPTH > 0 AND (C = ',' OR C = '}') THEN
GOTO RETURN;
IF C = '{' THEN BEGIN
REF(TUPLE) X;
X :- GETGROUP(S.SUB(2,S.LENGTH-1), DEPTH + 1);
IF X =/= NONE THEN BEGIN
REF(TEXTARRAYLIST) OUT2;
INTEGER A,B;
! OUT,S = [A+B FOR A IN OUT FOR B IN X[0]], X[1] ;
OUT2 :- NEW TEXTARRAYLIST;
FOR A := 1 STEP 1 UNTIL OUT.SIZE DO
FOR B := 1 STEP 1 UNTIL X.TLIST.SIZE DO
OUT2.ADD(OUT.GET(A) & X.TLIST.GET(B));
OUT :- OUT2;
S :- X.T;
GOTO CONTINUE;
END;
END;
IF C = '\' AND S.LENGTH > 1 THEN BEGIN
TEXT NEWCTEXT;
NEWCTEXT :- BLANKS(CTEXT.LENGTH + 1);
NEWCTEXT := CTEXT;
NEWCTEXT.SETPOS(CTEXT.LENGTH+1);
S.SETPOS(2); NEWCTEXT.PUTCHAR(S.GETCHAR);
CTEXT :- NEWCTEXT;
S :- S.SUB(2,S.LENGTH-1);
END;
BEGIN
REF(TEXTARRAYLIST) OUT2;
INTEGER A;
! OUT, S = [A+CTEXT FOR A IN OUT], S[1:] ;
OUT2 :- NEW TEXTARRAYLIST;
FOR A := 1 STEP 1 UNTIL OUT.SIZE DO
OUT2.ADD(OUT.GET(A) & CTEXT);
OUT :- OUT2;
S :- S.SUB(2,S.LENGTH-1);
END;
END;
RETURN:
RESULT :- NEW TUPLE(OUT,S);
GETITEM :- RESULT;
END GETITEM;
REF(TUPLE) PROCEDURE GETGROUP(S, DEPTH);
TEXT S;
INTEGER DEPTH;
BEGIN
REF(TUPLE) RESULT;
REF(TEXTARRAYLIST) OUT;
BOOLEAN COMMA,BREAK;
OUT :- NEW TEXTARRAYLIST;
COMMA := FALSE;
BREAK := FALSE;
WHILE S.LENGTH > 0 AND NOT BREAK DO BEGIN
REF(TUPLE) GS;
REF(TEXTARRAYLIST) G;
GS :- GETITEM(S, DEPTH); G :- GS.TLIST; S :- GS.T;
IF S.LENGTH = 0 THEN BREAK := TRUE ELSE
BEGIN
CHARACTER S1;
INTEGER I;
! out += g ;
FOR I := 1 STEP 1 UNTIL G.SIZE DO OUT.ADD(G.GET(I));
S.SETPOS(1); S1 := S.GETCHAR;
IF S1 = '}' THEN BEGIN
IF COMMA THEN BEGIN
BREAK := TRUE;
RESULT :- NEW TUPLE(OUT, S.SUB(2,S.LENGTH-1));
END ELSE
BEGIN
REF(TEXTARRAYLIST) OUT2;
INTEGER I;
OUT2 :- NEW TEXTARRAYLIST;
FOR I := 1 STEP 1 UNTIL OUT.SIZE DO
OUT2.ADD("{" & OUT.GET(I) & "}");
BREAK := TRUE;
RESULT :- NEW TUPLE(OUT2, S.SUB(2,S.LENGTH-1));
END;
END ELSE
IF S1 = ',' THEN BEGIN
COMMA := TRUE;
S :- S.SUB(2,S.LENGTH-1);
END;
END;
END;
GETGROUP :- RESULT;
END GETGROUP;
TEXT INP;
FOR INP :- "~/{Downloads,Pictures}/*.{jpg,gif,png}",
"It{{em,alic}iz,erat}e{d,}, please.",
"{,{,gotta have{ ,\, again\, }}more }cowbell!",
"{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}" DO
BEGIN
REF(TUPLE) RES;
INTEGER I;
RES :- GETITEM(INP,0);
OUTTEXT(INP);
OUTIMAGE;
FOR I := 1 STEP 1 UNTIL RES.TLIST.SIZE DO BEGIN
OUTTEXT(" ");
OUTTEXT(RES.TLIST.GET(I));
OUTIMAGE;
END;
OUTIMAGE;
END;
END- Output:
~/{Downloads,Pictures}/*.{jpg,gif,png}
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
It{{em,alic}iz,erat}e{d,}, please.
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
Tailspin
templates braceExpansion
composer braceParse
[ <part|'[{}\\,]'>* ] // This is not simply <production> because there may be unbalanced special chars
rule production: [ <part>* ]
rule part: <alternation|balancedBraces|escapedCharacter|'[^{}\\,]+'>+
rule alternation: (<='{'>) [ <production> <alternate>+ ] (<='}'>)
rule alternate: (<=','>) <production>
rule balancedBraces: <='{'> <part>* <='}'>
rule escapedCharacter: <'\\.'>
end braceParse
templates collateSequence
data part <[]|''> local
@: [''];
$... -> #
$@!
when <´part´ '.*'> do
def part: $;
@: [$@... -> '$;$part;'];
otherwise
def alternates: [ $... -> collateSequence ... ];
@: [$@... -> \(def prefix: $; $alternates... -> '$prefix;$;' ! \)];
end collateSequence
$ -> braceParse -> collateSequence !
end braceExpansion
'~/{Downloads,Pictures}/*.{jpg,gif,png}' -> '"$;" expands to:$ -> braceExpansion ... -> '$#10;$;';$#10;$#10;' -> !OUT::write
'It{{em,alic}iz,erat}e{d,}, please.' -> '"$;" expands to $ -> braceExpansion ... -> '$#10;$;';$#10;$#10;' -> !OUT::write
'{,{,gotta have{ ,\, again\, }}more }cowbell!' -> '"$;" expands to $ -> braceExpansion ... -> '$#10;$;';$#10;$#10;' -> !OUT::write
'{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}' -> '"$;" expands to $ -> braceExpansion ... -> '$#10;$;';$#10;$#10;' -> !OUT::write- Output:
"~/{Downloads,Pictures}/*.{jpg,gif,png}" expands to:
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
"It{{em,alic}iz,erat}e{d,}, please." expands to
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
"{,{,gotta have{ ,\, again\, }}more }cowbell!" expands to
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
"{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}" expands to
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
Tcl
package require Tcl 8.6
proc combine {cases1 cases2 {insert ""}} {
set result {}
foreach c1 $cases1 {
foreach c2 $cases2 {
lappend result $c1$insert$c2
}
}
return $result
}
proc expand {string *expvar} {
upvar 1 ${*expvar} expanded
set a {}
set result {}
set depth 0
foreach token [regexp -all -inline {(?:[^\\{},]|\\.)+|[\\{},]} $string] {
switch $token {
"," {
if {$depth == 0} {
lappend result {*}[commatize $a]
set a {}
set expanded 1
continue
}
}
"\{" {incr depth 1}
"\}" {incr depth -1}
}
append a $token
}
lappend result {*}[commatize $a]
return $result
}
proc commatize {string} {
set current {{}}
set depth 0
foreach token [regexp -all -inline {(?:[^\\{},]|\\.)+|[\\{},]} $string] {
switch $token {
"\{" {
if {[incr depth] == 1} {
set collect {}
continue
}
}
"\}" {
if {[incr depth -1] == 0} {
set foundComma 0
set exp [expand $collect foundComma]
if {!$foundComma} {
set exp [lmap c [commatize $collect] {set c \{$c\}}]
}
set current [combine $current $exp]
continue
} elseif {$depth < 0} {
set depth 0
}
}
}
if {$depth} {
append collect $token
} else {
set current [lmap s $current {set s $s$token}]
}
}
if {$depth} {
set current [combine $current [commatize $collect] "\{"]
}
return $current
}
Demonstrating:
foreach testcase {
"~/{Downloads,Pictures}/*.{jpg,gif,png}"
"It{{em,alic}iz,erat}e{d,}, please."
"{,{,gotta have{ ,\\, again\\, }}more }cowbell!"
"\{\}\} some \}\{,\{\\\\\{ edge, edge\} \\,\}\{ cases, \{here\} \\\\\\\\\\\}"
} {
puts $testcase\n\t[join [commatize $testcase] \n\t]
}
- Output:
~/{Downloads,Pictures}/*.{jpg,gif,png}
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
It{{em,alic}iz,erat}e{d,}, please.
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
TXR
The approach here is to parse the notation into a nested tree of strings. In the following diagram the -> arrow indicates that the tree on the left denotes the list of output strings on the right.
A list with no operator symbol denotes catenation:
("foo" "bar") -> ("foobar")
The / symbol (slash, usually denoting arithmetic division) denotes alternation:
(/ "foo" "bar") -> ("foo" "bar")
("inter" (/ "pol" "pret") "ation") -> ("interpolation" "interpretation")
This notation is processed by the bexp-expand function to produce the list of strings which it denotes. The bexp-parse function parses a string containing brace expansion into the above notation.
The backslashes and edge cases are handled between the tokenizing and parsing. Backslashed characters are represented as tokens which include the backslash. Thus the \{ token compares unequal to { and isn't mistaken for it. These backslashed tokens just look like any other text that has no special meaning.
The empty {} is handled as a token, but other cases of braces containing no commas are handled in the parser.
When the parser has scanned a complete, valid brace that contains no comma, instead of generating a (/ ...) tree node from the content, it generates ("{" ... "}"), rendering the braces as literal strings. The ... content may contain / operators, as required.
When the parser has scanned an incomplete brace, it puts out ("{" ...): the dangling brace is represented literally, followed by the items that have been parsed out. The comma elements are preserved in this case; the lack of a closing brace turns off their meaning.
In the main case of a balanced brace with commas, the parsed out elements are split on the commas, which are removed, and that forms the arguments of / node.
;; API
(defun brace-expand (str)
(bexp-expand (bexp-parse str)))
;; parser
(defstruct bexp-parse-ctx ()
str
toks)
(defun bexp-parse (str)
(let ((ctx (new bexp-parse-ctx
str str
;; tokenizer
toks (remqual "" (tok #/([{},]|{}|\\\\|\\.)/ t str)))))
(build
(whilet ((next (pop ctx.toks)))
(add
(if (equal next "{")
(bexp-parse-brace ctx)
next))))))
(defun bexp-parse-brace (ctx)
(buildn
(let ((orig-toks ctx.toks))
(caseq (whilet ((next (pop ctx.toks)))
(casequal next
("{" (add (bexp-parse-brace ctx)))
("}" (return :ok))
(t (add next))))
(:ok
(cond
((memqual "," (get))
(flow (get)
(split* @1 (op where (op equal ",")))
(cons '/)))
(t
(add* "{")
(add "}")
(get))))
(nil
(add* "{")
(get))))))
;; expander
(defun bexp-expand (tree : (path (new list-builder)))
(build
(match-case tree
(() (add (cat-str path.(get))))
(((/ . @alt) . @rest)
(let ((saved-path path.(get)))
(each ((elem alt))
path.(oust saved-path)
(pend (bexp-expand (cons elem rest) path)))))
((@(consp @succ) . @rest)
(pend (bexp-expand (append succ rest) path)))
((@head . @rest)
path.(add head)
(pend (bexp-expand rest path))))))
;; Tests
(tprint (brace-expand "~/{Downloads,Pictures}/*.{jpg,gif,png}"))
(tprint (brace-expand "It{{em,alic}iz,erat}e{d,}, please."))
(tprint (brace-expand "{,{,gotta have{ ,\\, again\\, }}more }cowbell!"))
(tprint (brace-expand "{}} some }{,{\\\\{ edge, edge} \\,}{ cases, {here} \\\\\\\\\\}"))- Output:
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
Visual Basic .NET
Module Module1
Function GetGroup(s As String, depth As Integer) As Tuple(Of List(Of String), String)
Dim out As New List(Of String)
Dim comma = False
While Not String.IsNullOrEmpty(s)
Dim gs = GetItem(s, depth)
Dim g = gs.Item1
s = gs.Item2
If String.IsNullOrEmpty(s) Then
Exit While
End If
out.AddRange(g)
If s(0) = "}" Then
If comma Then
Return Tuple.Create(out, s.Substring(1))
End If
Return Tuple.Create(out.Select(Function(a) "{" + a + "}").ToList(), s.Substring(1))
End If
If s(0) = "," Then
comma = True
s = s.Substring(1)
End If
End While
Return Nothing
End Function
Function GetItem(s As String, Optional depth As Integer = 0) As Tuple(Of List(Of String), String)
Dim out As New List(Of String) From {""}
While Not String.IsNullOrEmpty(s)
Dim c = s(0)
If depth > 0 AndAlso (c = "," OrElse c = "}") Then
Return Tuple.Create(out, s)
End If
If c = "{" Then
Dim x = GetGroup(s.Substring(1), depth + 1)
If Not IsNothing(x) Then
Dim tout As New List(Of String)
For Each a In out
For Each b In x.Item1
tout.Add(a + b)
Next
Next
out = tout
s = x.Item2
Continue While
End If
End If
If c = "\" AndAlso s.Length > 1 Then
c += s(1)
s = s.Substring(1)
End If
out = out.Select(Function(a) a + c).ToList()
s = s.Substring(1)
End While
Return Tuple.Create(out, s)
End Function
Sub Main()
For Each s In {
"It{{em,alic}iz,erat}e{d,}, please.",
"~/{Downloads,Pictures}/*.{jpg,gif,png}",
"{,{,gotta have{ ,\, again\, }}more }cowbell!",
"{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}"
}
Dim fmt = "{0}" + vbNewLine + vbTab + "{1}"
Dim parts = GetItem(s)
Dim res = String.Join(vbNewLine + vbTab, parts.Item1)
Console.WriteLine(fmt, s, res)
Next
End Sub
End Module
- Output:
It{{em,alic}iz,erat}e{d,}, please.
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
~/{Downloads,Pictures}/*.{jpg,gif,png}
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
{,{,gotta have{ ,\, again\, }}more }cowbell!
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\ again\ more cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
{}} some }{,{\ edge \}{ cases, {here} \\\
{}} some }{,{\ edge \}{ cases, {here} \\\
Wren
var getGroup // forward declaration
var getItem = Fn.new { |s, depth|
var out = [""]
while (s != "") {
var c = s[0]
if (depth > 0 && (c == "," || c == "}")) return [out, s]
var cont = false
if (c == "{") {
var x = getGroup.call(s[1..-1], depth+1)
if (!x[0].isEmpty) {
var t = []
for (a in out) {
for (b in x[0]) {
t.add(a + b)
}
}
out = t
s = x[1]
cont = true
}
}
if (!cont) {
if (c == "\\" && s.count > 1) {
c = c + s[1]
s = s[1..-1]
}
out = out.map { |a| a + c }.toList
s = s[1..-1]
}
}
return [out, s]
}
getGroup = Fn.new { |s, depth|
var out = []
var comma = false
while (s != "") {
var t = getItem.call(s, depth)
var g = t[0]
s = t[1]
if (s == "") break
out.addAll(g)
if (s[0] == "}") {
if (comma) return [out, s[1..-1]]
return [out.map { |a| "{" + a + "}" }.toList, s[1..-1]]
}
if (s[0] == ",") {
comma = true
s = s[1..-1]
}
}
return [[], ""]
}
var inputs = [
"~/{Downloads,Pictures}/*.{jpg,gif,png}",
"It{{em,alic}iz,erat}e{d,}, please.",
"{,{,gotta have{ ,\\, again\\, }}more }cowbell!",
"{}} some }{,{\\\\{ edge, edge} \\,}{ cases, {here} \\\\\\\\\\}"
]
for (input in inputs) {
System.print(input)
for (s in getItem.call(input, 0)[0]) System.print(" " + s)
System.print()
}
- Output:
~/{Downloads,Pictures}/*.{jpg,gif,png}
~/Downloads/*.jpg
~/Downloads/*.gif
~/Downloads/*.png
~/Pictures/*.jpg
~/Pictures/*.gif
~/Pictures/*.png
It{{em,alic}iz,erat}e{d,}, please.
Itemized, please.
Itemize, please.
Italicized, please.
Italicize, please.
Iterated, please.
Iterate, please.
{,{,gotta have{ ,\, again\, }}more }cowbell!
cowbell!
more cowbell!
gotta have more cowbell!
gotta have\, again\, more cowbell!
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}
zkl
This is a two pass algorithm (2*length(string)), one pass to find valid {} pairs, the next pass to expand them.
fcn eyeball(code,ps=L(),brace=False){ //-->indexes of valid braces & commas
cs:=L();
foreach c in (code){ // start fresh or continue (if recursing)
switch(c){
case("\\"){ __cWalker.next(); }
case(",") { if(brace) cs.append(__cWalker.n); } // maybe valid
case("{") { // this is real only if there is matching } and a comma
n:=__cWalker.n;
_,cz:=self.fcn(__cWalker,ps,True);
if(cz){ ps.append(n,__cWalker.n); ps.extend(cz) } // valid {} pair
}
case("}"){ if(brace) return(ps,cs); }
}
}
return(ps,False)
}
fcn expando(code,strings=T("")){
reg [const] stack=List(); reg roots,cs; bs,_:=eyeball(code);
foreach c in (code){
if(bs.holds(__cWalker.n)){
if (c=="{") { stack.append(cs); cs=0; roots=strings; }
else if(c==",") { stack.append(strings); strings=roots; cs+=1; }
else if(c=="}") { do(cs){ strings=stack.pop().extend(strings); } cs=stack.pop(); }
}else if(c=="\\"){
c="\\"+__cWalker.next();
strings=strings.apply('+(c));
}
else strings=strings.apply('+(c));
}
strings
}foreach bs in (T("It{{em,alic}iz,erat}e{d,}", "~/{Downloads,Pictures}/*.{jpg,gif,png}",
"It{{em,alic}iz,erat}e{d,}, please.", "a{2,1}b{X,Y,X}c", 0'|a\\{\\\{b,c\,d}|,
"{a,b{c{,{d}}e}f", 0'|{,{,gotta have{ ,\, again\, }}more }cowbell!|,
0'|{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\}|))
{
"%s expands to\n %s".fmt(bs,expando(bs)).println();
}- Output:
It{{em,alic}iz,erat}e{d,} expands to
L("Itemized","Italicized","Iterated","Itemize","Italicize","Iterate")
~/{Downloads,Pictures}/*.{jpg,gif,png} expands to
L("~/Downloads/*.jpg","~/Pictures/*.jpg","~/Downloads/*.gif","~/Pictures/*.gif","~/Downloads/*.png","~/Pictures/*.png")
It{{em,alic}iz,erat}e{d,}, please. expands to
L("Itemized, please.","Italicized, please.","Iterated, please.","Itemize, please.","Italicize, please.","Iterate, please.")
a{2,1}b{X,Y,X}c expands to
L("a2bXc","a1bXc","a2bYc","a1bYc","a2bXc","a1bXc")
a\\{\\\{b,c\,d} expands to
L("a\\\\\{b","a\\c\,d")
{a,b{c{,{d}}e}f expands to
L("{a,b{ce}f","{a,b{c{d}e}f")
{,{,gotta have{ ,\, again\, }}more }cowbell! expands to
L("cowbell!","more cowbell!","gotta have more cowbell!","gotta have\, again\, more cowbell!")
{}} some }{,{\\{ edge, edge} \,}{ cases, {here} \\\\\} expands to
L("{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}","{}} some }{,{\\ edge \,}{ cases, {here} \\\\\}")
Categories:
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