Range extraction
You are encouraged to solve this task according to the task description, using any language you may know.
A format for expressing an ordered list of integers is to use a comma separated list of either
- individual integers
- Or a range of integers denoted by the starting integer separated from the end integer in the range by a dash, '-'. (The range includes all integers in the interval including both endpoints)
- The range syntax is to be used only for, and for every range that expands to more than two values.
Example
The list of integers:
- -6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20
Is accurately expressed by the range expression:
- -6,-3-1,3-5,7-11,14,15,17-20
(And vice-versa).
The task
- Create a function that takes a list of integers in increasing order and returns a correctly formatted string in the range format.
- Use the function to compute and print the range formatted version of the following ordered list of integers:
0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39
- Show the output of your program.
C.f. Range expansion
Ada
The provided solutions return an empty string, if the Sequence of integers is empty. Ranges with negative bounds are represented as -9--4, as the task requires. For real-life applications it is better to use the notation -9..-4.
Iterative Solution
Since we don't know in advance how long the output will be, the iterative solution uses Unbounded_Strings.
<lang Ada>with Ada.Text_IO; use Ada.Text_IO; with Ada.Strings.Unbounded; use Ada.Strings.Unbounded; with Ada.Strings.Fixed; use Ada.Strings.Fixed;
procedure Range_Extraction is
type Sequence is array (Positive range <>) of Integer;
function Image (S : Sequence) return String is
Result : Unbounded_String;
From : Integer;
procedure Flush (To : Integer) is
begin
if Length (Result) > 0 then
Append (Result, ',');
end if;
Append (Result, Trim (Integer'Image (From), Ada.Strings.Left));
if From < To then
if From+1 = To then
Append (Result, ',');
else
Append (Result, '-');
end if;
Append (Result, Trim (Integer'Image (To), Ada.Strings.Left));
end if;
end Flush;
begin
if S'Length > 0 then
From := S (S'First);
for I in S'First + 1..S'Last loop
if S (I - 1) + 1 /= S (I) then
Flush (S (I - 1));
From := S (I);
end if;
end loop;
Flush (S (S'Last));
end if;
return To_String (Result);
end Image;
begin
Put_Line
( Image
( ( 0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39
) ) );
end Range_Extraction;</lang>
Recursive Solution
The recursive solution avoids the usage of unbounded strings.
<lang Ada>with Ada.Text_IO, Ada.Strings.Fixed;
procedure Range_Extract is
type Sequence is array (Positive range <>) of Integer;
function Img(I: Integer) return String is -- the image of an Integer
begin
return
Ada.Strings.Fixed.Trim(Integer'Image(I), Ada.Strings.Left);
end Img;
function Img(S: Sequence) return String is -- the image of a Sequence
function X(S : Sequence) return String is -- recursive eXtract
Idx: Positive := S'First;
begin
if S'Length = 0 then return
""; -- return nothing if Sequence is empty
else
while Idx < S'Last and then S(Idx+1) = S(Idx) + 1 loop
Idx := Idx + 1;
end loop;
if Idx = S'First then return
"," & Img(S(Idx)) & X(S(Idx+1 .. S'Last));
elsif Idx = S'First+1 then return
"," & Img(S(S'First)) & ',' & Img(S(Idx)) & X(S(Idx+1 .. S'Last));
else return
"," & Img(S(S'First)) & '-' & Img(S(Idx)) & X(S(Idx+1 .. S'Last));
end if;
end if;
end X;
begin -- function Img(S: Sequence) return String
if S'Length = 0 then return
"";
else return
Img(S(S'First)) & X(S(S'First+1 .. S'Last));
end if;
end Img;
begin -- main
Ada.Text_IO.Put_Line(Img( ( 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16,
17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29,
30, 31, 32, 33, 35, 36, 37, 38, 39) ));
end Range_Extract;</lang>
Sample output
The sample output is exactly the same, for both solutions:
0-2,4,6-8,11,12,14-25,27-33,35-39
Aime
<lang aime>void fs(integer &s, data b) {
if (s) {
b_append(b, ',');
} s = 1;
}
text rp(...) {
integer f, i, j; data b;
f = 0;
i = 0;
j = 0;
while (i < count()) {
while (j < count() - 1) { if (__integer(lead(j + 1)) == __integer(lead(j)) + 1) { j += 1; } else { break; } } if (i + 1 < j) { fs(f, b); b_suffix(b, itoa(lead(i))); b_append(b, '-'); b_suffix(b, itoa(lead(j))); } else { while (i < j + 1) { fs(f, b); b_suffix(b, itoa(lead(i))); i += 1; } } j += 1; i = j;
}
return b_string(b);
}
integer main(void) {
o_text(rp(0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39));
o_byte('\n');
return 0;
}</lang>
Output
0-2,4,6-8,11,12,14-25,27-33,35-39
ALGOL 68
Note: The following Iterative code specimen is the "unrolled" version of the Generative code specimen below. Together they provided as a comparison of the two different methods.
Iterative
- The closest concept that Algol 68 has to duck typing is the tagged union. This is used to define mode urange = union(int, struct(int lwb, upb)). If duck typing was available it could reduced the size of the code specimen, but would have lost some of Algol 68's strong type data security.
File: Template_Range_extraction_Base.a68 <lang algol68>###
REQUIRES(MODE SCALAR, OP(SCALAR,SCALAR)BOOL =, OP(SCALAR,SCALAR)SCALAR +);
MODE SCALARLIST = FLEX[0]SCALAR; MODE YIELDINT = PROC(SCALAR)VOID;
- Declarations for manipulating lists of range pairs [lwb:upb] #
MODE RANGE = STRUCT(SCALAR lwb, upb); MODE RANGELIST = FLEX[0]RANGE; MODE YIELDRANGE = PROC(RANGE)VOID;
PROC range repr = (RANGE range)STRING: (
STRING lwb := whole(lwb OF range,0); IF lwb OF range = upb OF range THEN lwb ELSE # "["+lwb+":"+whole(upb OF range,0)+"]" # lwb+"-"+whole(upb OF range,0) FI
);
- OP REPR = (RANGE range)STRING: range repr(range); # # firmly related to UNIRANGE #
- Declarations for manipulating lists containing pairs AND lone INTs #
MODE UNIRANGE = UNION(SCALAR, RANGE); MODE UNIRANGELIST = FLEX[0]UNIRANGE; MODE YIELDUNIRANGE = PROC(UNIRANGE)VOID;
PROC unirange repr = (UNIRANGE unirange)STRING:
CASE unirange IN (RANGE range): range repr(range), (SCALAR scalar): whole(scalar,0) ESAC;
OP (UNIRANGE)STRING REPR = unirange repr; # alias #
- The closest thing Algol68 has to inheritance is the UNION #
MODE UNIRANGELISTS = UNION(UNIRANGELIST, RANGELIST, SCALARLIST);
PROC unirange list repr = (UNIRANGELIST unirange list)STRING: (
- Produce a STRING representation of a UNIRANGELIST ###
STRING out # := "("#, sep := "";
FOR key FROM LWB unirange list TO UPB unirange list DO
out +:= sep + REPR unirange list[key];
sep := "," # +" " #
OD;
out # +")" #
);
OP (UNIRANGELIST)STRING REPR = unirange list repr; # alias #</lang>File: Template_Range_extraction_Iterative.a68 <lang algol68>###
REQUIRES(MODE SCALAR, OP(SCALAR,SCALAR)BOOL =, OP(SCALAR,SCALAR)SCALAR +);
PR READ "Template_Range_extraction_Base.a68" PR
OP (UNIRANGELISTS)UNIRANGELIST INITUNIRANGE = init unirange list; # alias #
PROC init unirange list = (UNIRANGELISTS unirange list)UNIRANGELIST: (
- Take a []SCALAR, []RANGE or []UNIRANGE, and return a normalised []UNIRANGE ###
INT len = UPB unirange list-LWB unirange list+1; [LWB unirange list: LWB unirange list+len*2]UNIRANGE out unirange list; SCALAR upb out unirange list := LWB out unirange list - 1; UNION(VOID, RANGE) prev range := EMPTY;
PROC out unirange list append = (RANGE value)VOID:(
IF lwb OF value = upb OF value THEN
out unirange list[upb out unirange list+:=1] := lwb OF value
ELIF lwb OF value + 1 = upb OF value THEN
out unirange list[upb out unirange list+:=1] := lwb OF value;
out unirange list[upb out unirange list+:=1] := upb OF value
ELSE
out unirange list[upb out unirange list+:=1] := value
FI
);
FOR key FROM LWB unirange list TO UPB unirange list DO
UNIRANGE value = CASE unirange list IN
(SCALARLIST list):list[key],
(RANGELIST list):list[key],
(UNIRANGELIST list):list[key]
ESAC;
RANGE next range := CASE value IN
(RANGE range): range,
(SCALAR value): RANGE(value, value)
ESAC;
prev range :=
CASE prev range IN
(VOID): next range,
(RANGE prev range):
IF upb OF prev range + 1 = lwb OF next range THEN
RANGE(lwb OF prev range, upb OF next range) # merge the range #
ELSE
out unirange list append(prev range);
next range
FI
OUT SKIP
ESAC
OD;
CASE prev range IN (RANGE last range): out unirange list append(last range) ESAC;
out unirange list[:upb out unirange list]
);</lang>File: test_Range_extraction_Integer.a68<lang algol68>#!/usr/local/bin/a68g --script #
- some simple test cases: #
MODE SCALAR = INT; PR READ "Template_Range_extraction_Iterative.a68" PR
- PR READ "Template_Range_extraction_Generative.a68" PR#
MODE RANGEINT = UNIRANGE;
test: BEGIN
[]INT int list = ( # unnormalised # 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39);
[]RANGE range list = ( # unnormalised # (0,0), (1,1), (2,2), (4,4), (6,6), (7,7), (8,8), (11,11), (12,12), (14,14), (15,15), (16,16), (17,17), (18,18), (19,19), (20,20), (21,21), (22,22), (23,23), (24,24), (25,25), (27,27), (28,28), (29,29), (30,30), (31,31), (32,32), (33,33), (35,35), (36,36), (37,37), (38,38), (39,39));
[]RANGEINT list a = ( # unnormalised # RANGE(0,2), 4, RANGE(6,8), RANGE(11,12), RANGE(14,25), RANGE(27,33), RANGE(35,39));
[]RANGEINT list b = ( # unnormalised # 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39);
[]RANGEINT list c = INITUNIRANGE(list b); # normalised #
- compare manipulation of various types of argument lists #
printf(($gl$, REPR INITUNIRANGE int list, REPR INITUNIRANGE range list, REPR INITUNIRANGE list a, REPR INITUNIRANGE list b, REPR list c ))
END</lang> Output:
0-2,4,6-8,11,12,14-25,27-33,35-39 0-2,4,6-8,11,12,14-25,27-33,35-39 0-2,4,6-8,11,12,14-25,27-33,35-39 0-2,4,6-8,11,12,14-25,27-33,35-39 0-2,4,6-8,11,12,14-25,27-33,35-39
Generative
- The following code a set of helper functions/generators that can be used to manipulate a lists of ranges. They can manipulate either arrays or iterator. And they can handle data of type int or range and both these types unioned.
These chained iterators do the following steps:
- Iterate through three different types of initial arrays - []int, []range and []unirange with gen range, yielding range(lwb,upb)
- Iterate with gen range merge yielding merged range(lwb,upb)
- Iterate with gen unirange merge, merging and yielding a union of int and range
- Finally iterate with unirange list init exiting with an array of union of int and range.
File: Template_Range_extraction_Generative.a68 <lang algol68>###
REQUIRES(MODE SCALAR, OP(SCALAR,SCALAR)BOOL =, OP(SCALAR,SCALAR)SCALAR +);
PR READ "Template_Range_extraction_Base.a68" PR
PROC gen range = (UNIRANGELISTS unirange list, YIELDRANGE yield range)VOID:
- Take a []SCALAR, []RANGE or []URANGE, and generatively yield an unnormalised RANGE ###
FOR key FROM LWB unirange list TO UPB unirange list DO
- Note: Algol 68RS cannot handle LWB and UPB of a UNION in the following: #
UNIRANGE value = CASE unirange list IN
(SCALARLIST list):list[key],
(RANGELIST list):list[key],
(UNIRANGELIST list):list[key]
ESAC;
yield range(
CASE value IN
(RANGE range): range,
(SCALAR value): (value, value)
ESAC
)
OD;
PROC gen range merge = (UNIRANGELISTS unirange list, YIELDRANGE yield)VOID: (
- Take a []SCALAR, []RANGE or []URANGE , and generatively yield a normalised RANGE ###
UNION(VOID, RANGE) prev range := EMPTY;
- FOR RANGE next range IN # gen range(unirange list, # ) DO #
- (RANGE next range)VOID:
- if the ranges cannot be merge, then yield 1st, and return 2nd #
prev range :=
CASE prev range IN
(VOID): next range,
(RANGE prev range):
IF upb OF prev range + 1 = lwb OF next range THEN
RANGE(lwb OF prev range, upb OF next range) # merge the range #
ELSE
#IF lwb OF prev range <= upb OF prev range THEN#
yield(prev range);
#FI;#
next range
FI
OUT SKIP
ESAC
- OD # );
CASE prev range IN (RANGE last range): yield(last range) ESAC
);
PROC gen unirange merge = (UNIRANGELISTS unirange list, YIELDUNIRANGE yield)VOID: (
- Take a []SCALAR, []RANGE or []UNIRANGE and generatively yield a normalised UNIRANGE ###
PROC unpack = (RANGE value)VOID:(
IF lwb OF value = upb OF value THEN
yield(lwb OF value)
ELIF lwb OF value + 1 = upb OF value THEN
yield(lwb OF value);
yield(upb OF value)
ELSE
yield(value)
FI
);
gen range merge(unirange list, unpack)
);
PROC unirange list init = (UNIRANGELISTS unirange list)UNIRANGELIST: (
- Take a []SCALAR, []RANGE or []UNIRANGE and return a static []UNIRANGE ###
INT len = UPB unirange list - LWB unirange list + 1; [LWB unirange list: LWB unirange list + len * 2]UNIRANGE out unirange list; # estimate # SCALAR upb out unirange list := LWB out unirange list - 1;
- FOR UNIRANGE unirange IN # gen unirange merge(unirange list, # ) DO #
- (UNIRANGE unirange)VOID:
out unirange list[upb out unirange list+:=1] := unirange
- OD # );
out unirange list[:upb out unirange list]
);
OP (UNIRANGELISTS)UNIRANGELIST INITUNIRANGE = unirange list init; # alias #</lang> Output:
0-2,4,6-8,11,12,14-25,27-33,35-39 0-2,4,6-8,11,12,14-25,27-33,35-39 0-2,4,6-8,11,12,14-25,27-33,35-39 0-2,4,6-8,11,12,14-25,27-33,35-39 0-2,4,6-8,11,12,14-25,27-33,35-39
AutoHotkey
<lang AutoHotkey>msgbox % extract("0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39")
extract( list ) {
loop, parse, list, `,, %A_Tab%%A_Space%`r`n
{
if (A_LoopField+0 != p+1)
ret .= (f!=p ? (p>f+1 ? "-" : ",") p : "") "," f := A_LoopField
p := A_LoopField
}
return SubStr(ret (f!=p ? (p>f+1 ? "-" : ",") p : ""), 2)
}</lang>
Output:
--------------------------- Range extraction.ahk --------------------------- 0-2,4,6-8,11,12,14-25,27-33,35-39 --------------------------- OK ---------------------------
Bracmat
<lang bracmat> ( rangeExtract
= accumulator firstInRange nextInRange
, accumulate fasten rangePattern
. ( accumulate
= !accumulator
(!accumulator:|?&",")
!firstInRange
( !firstInRange+1:<>!nextInRange
& ( !firstInRange+2:!nextInRange&","
| "-"
)
-1+!nextInRange
|
)
: ?accumulator
)
& ( fasten
= [%( !accumulate
& (!sjt:?firstInRange)+1:?nextInRange
)
)
& ( rangePattern
= (
| ?
( !nextInRange
& 1+!nextInRange:?nextInRange
)
)
( &!accumulate
| (#<>!nextInRange:!fasten) !rangePattern
)
)
& :?accumulator:?firstInRange
& !arg:(|#!fasten !rangePattern)
& str$!accumulator
)
& ( test
= L A
. put$(!arg " ==>\n",LIN)
& ( !arg:(?,?)
& whl'(!arg:(?A,?arg)&(!A,!L):?L)
& whl'(!L:(?A,?L)&!A !arg:?arg)
|
)
& out$(rangeExtract$!arg)
)
& test
$ (0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39)</lang>
Output:
(0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39) ==> 0-2,4,6-8,11,12,14-25,27-33,35-39
C
Using the fine tradition of snprintf, rprint is not responsible for allocating output buffer. It prints the range only if supplied a non-null pointer, but always returns the output length sans the terminating null, so caller can allocate buffer.
<lang c>#include <stdio.h>
- include <stdlib.h>
size_t rprint(char *s, int *x, int len) {
- define sep (a > s ? "," : "") /* use comma except before first output */
- define ol (s ? 100 : 0) /* print only if not testing for length */
int i, j; char *a = s; for (i = j = 0; i < len; i = ++j) { for (; j < len - 1 && x[j + 1] == x[j] + 1; j++);
if (i + 1 < j) a += snprintf(s?a:s, ol, "%s%d-%d", sep, x[i], x[j]); else while (i <= j) a += snprintf(s?a:s, ol, "%s%d", sep, x[i++]); } return a - s;
- undef sep
- undef ol
}
int main() { int x[] = { 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39 };
char *s = malloc(rprint(0, x, sizeof(x) / sizeof(int)) + 1); rprint(s, x, sizeof(x) / sizeof(int)); printf("%s\n", s);
return 0; }</lang>output<lang>0-2,4,6-8,11,12,14-25,27-33,35-39</lang>
C++
<lang cpp>
- include <iostream>
- include <iterator>
- include <cstddef>
template<typename InIter>
void extract_ranges(InIter begin, InIter end, std::ostream& os)
{
if (begin == end) return;
int current = *begin++; os << current; int count = 1;
while (begin != end)
{
int next = *begin++;
if (next == current+1)
++count;
else
{
if (count > 2)
os << '-';
else
os << ',';
if (count > 1)
os << current << ',';
os << next;
count = 1;
}
current = next;
}
if (count > 1) os << (count > 2? '-' : ',') << current;
}
template<typename T, std::size_t n>
T* end(T (&array)[n])
{
return array+n;
}
int main() {
int data[] = { 0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39 };
extract_ranges(data, end(data), std::cout); std::cout << std::endl;
} </lang> Output:
0-2,4,6-8,11,12,14-25,27-33,35-39
C#
Made a fix to this very idiosyncratic code. <lang csharp>using System; using System.Collections.Generic; using System.Linq;
class RangeExtraction {
static void Main()
{
const string testString = "0, 1, 2, 4, 6, 7, 8, 11, 12, 14,15, 16, 17, 18, 19, 20, 21, 22, 23, 24,25, 27, 28, 29, 30, 31, 32, 33, 35, 36,37, 38, 39";
var result = String.Join(",", RangesToStrings(GetRanges(testString)));
Console.Out.WriteLine(result);
}
public static IEnumerable<IEnumerable<int>> GetRanges(string testString)
{
var numbers = testString.Split(new[] { ',' }).Select(x => Convert.ToInt32(x));
var current = new List<int>();
foreach (var n in numbers)
{
if (current.Count == 0)
{
current.Add(n);
}
else
{
if (current.Max() + 1 == n)
{
current.Add(n);
}
else
{
yield return current;
current = new List<int> { n };
}
}
}
yield return current;
}
public static IEnumerable<string> RangesToStrings(IEnumerable<IEnumerable<int>> ranges)
{
foreach (var range in ranges)
{
if (range.Count() == 1)
{
yield return range.Single().ToString();
}
else if (range.Count() == 2)
{
yield return range.Min() + "," + range.Max();
}
else
{
yield return range.Min() + "-" + range.Max();
}
}
}
} </lang>
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39
Common Lisp
<lang lisp>(defun format-with-ranges (list)
(unless list (return ""))
(with-output-to-string (s)
(let ((current (first list))
(list (rest list))
(count 1))
(princ current s)
(dolist (next list)
(if (= next (1+ current))
(incf count)
(progn (princ (if (> count 2) "-" ",") s)
(when (> count 1)
(princ current s)
(princ "," s))
(princ next s)
(setf count 1)))
(setf current next))
(when (> count 1)
(princ (if (> count 2) "-" ",") s)
(princ current s)))))
CL-USER> (format-with-ranges (list 0 1 2 4 6 7 8 11 12 14
15 16 17 18 19 20 21 22 23 24
25 27 28 29 30 31 32 33 35 36
37 38 39))
"0-2,4,6-8,11,12,14-25,27-33,35-39" </lang>
D
<lang d>import std.stdio, std.conv, std.string, std.algorithm;
string extractRanges(in int[] items) in {
assert(items.isSorted());
} body {
string[] ranges;
for (size_t i = 0; i < items.length; i++) {
immutable low = items[i];
while (i < (items.length - 1) && (items[i] + 1) == items[i + 1])
i++;
immutable hi = items[i];
if (hi - low >= 2)
ranges ~= text(low, '-', hi);
else if (hi - low == 1)
ranges ~= text(low, ',', hi);
else
ranges ~= text(low);
}
return ranges.join(",");
}
void main() {
foreach (data; [[-8, -7, -6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9,
10, 11, 14, 15, 17, 18, 19, 20],
[0, 0, 0, 1, 1],
[0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18,
19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31,
32, 33, 35, 36, 37, 38, 39]])
writeln(extractRanges(data));
}</lang>
- Output:
-8--6,-3-1,3-5,7-11,14,15,17-20 0,0,0,1,1 0-2,4,6-8,11,12,14-25,27-33,35-39
DWScript
<lang delphi>procedure ExtractRanges(const values : array of Integer); begin
var i:=0;
while i<values.Length do begin
if i>0 then
Print(',');
Print(values[i]);
var j:=i+1;
while (j<values.Length) and (values[j]=values[j-1]+1) do
Inc(j);
Dec(j);
if j>i then begin
if j=i+1 then
Print(',')
else Print('-');
Print(values[j]);
end;
i:=j+1;
end;
end;
ExtractRanges([ 0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39]);</lang>
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39
E
Cheeky solution: relying on the standard library for finding ranges, and just formatting them ourselves.
<lang e>def rex(numbers :List[int]) {
var region := 0..!0
for n in numbers { region |= n..n }
var ranges := []
for interval in region.getSimpleRegions() {
def a := interval.getOptStart()
def b := interval.getOptBound() - 1
ranges with= if (b > a + 1) {
`$a-$b`
} else if (b <=> a + 1) {
`$a,$b`
} else { # b <=> a
`$a`
}
}
return ",".rjoin(ranges)
}</lang>
<lang e>? rex([ > 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, > 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, > 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, > 37, 38, 39])
- value: "0-2,4,6-8,11,12,14-25,27-33,35-39"
</lang>
Euphoria
<lang euphoria>function extract_ranges(sequence s)
integer first
sequence out
out = ""
if length(s) = 0 then
return out
end if
first = 1
for i = 2 to length(s) do
if s[i] != s[i-1]+1 then
if first = i-1 then
out &= sprintf("%d,", s[first])
elsif first = i-2 then
out &= sprintf("%d,%d,", {s[first],s[i-1]})
else
out &= sprintf("%d-%d,", {s[first],s[i-1]})
end if
first = i
end if
end for
if first = length(s) then
out &= sprintf("%d", s[first])
elsif first = length(s)-1 then
out &= sprintf("%d,%d", {s[first],s[$]})
else
out &= sprintf("%d-%d", {s[first],s[$]})
end if
return out
end function
puts(1, extract_ranges({0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19,
20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39}))</lang>
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39
F#
<lang fsharp>let extractRanges = function
| [] -> Seq.empty
| x::xr ->
let rec loop ys first last = seq {
match ys with
| y::yr when y = last + 1 -> yield! loop yr first y // add to current range
| y::yr -> yield (first, last) // finish current range
yield! loop yr y y // and start next
| [] -> yield (first, last) } // finish final range
loop xr x x
let rangeToString (s,e) =
match e-s with | 0 -> sprintf "%d" s | 1 -> sprintf "%d,%d" s e | _ -> sprintf "%d-%d" s e
let extract = extractRanges >> Seq.map rangeToString >> String.concat ","
printfn "%s" (extract [ 0; 1; 2; 4; 6; 7; 8; 11; 12; 14; 15; 16; 17; 18; 19; 20; 21;
22; 23; 24; 25; 27; 28; 29; 30; 31; 32; 33; 35; 36; 37; 38; 39 ])</lang>
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39
Forth
<lang forth>create values here
0 , 1 , 2 , 4 , 6 , 7 , 8 , 11 , 12 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 35 , 36 , 37 , 38 , 39 ,
here swap - 1 cells / constant /values
- clip 1- swap cell+ swap ; \ reduce array
- .range2 0 .r ." -" 0 .r ; \ difference two or more
- .range1 0 .r ." , " 0 .r ; \ difference one
- .range0 drop 0 .r ; \ no difference
\ select printing routine
create .range ' .range0 , ' .range1 , ' .range2 ,
does> >r over over - 2 min cells r> + @ execute ;
- .ranges ( a n --)
over @ dup >r >r \ setup first value begin clip dup \ check length array while over @ dup r@ 1+ = \ check if range breaks if r> drop >r else r> r> .range ." , " dup >r >r then repeat 2drop r> r> .range cr \ print last range
values /values .ranges</lang>
Output:
0-2, 4, 6-8, 11, 12, 14-25, 27-33, 35-39
Go
<lang go>package main
import (
"errors" "fmt" "strconv" "strings"
)
func main() {
rf, err := rangeFormat([]int{
0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39,
})
if err != nil {
fmt.Println(err)
return
}
fmt.Println("range format:", rf)
}
func rangeFormat(a []int) (string, error) {
if len(a) == 0 {
return "", nil
}
var parts []string
for n1 := 0; ; {
n2 := n1 + 1
for n2 < len(a) && a[n2] == a[n2-1]+1 {
n2++
}
s := strconv.Itoa(a[n1])
if n2 == n1+2 {
s += "," + strconv.Itoa(a[n2-1])
} else if n2 > n1+2 {
s += "-" + strconv.Itoa(a[n2-1])
}
parts = append(parts, s)
if n2 == len(a) {
break
}
if a[n2] == a[n2-1] {
return "", errors.New(fmt.Sprintf(
"sequence repeats value %d", a[n2]))
}
if a[n2] < a[n2-1] {
return "", errors.New(fmt.Sprintf(
"sequence not ordered: %d < %d", a[n2], a[n2-1]))
}
n1 = n2
}
return strings.Join(parts, ","), nil
}</lang> Output:
range format: 0-2,4,6-8,11,12,14-25,27-33,35-39
Groovy
Ad Hoc Solution: <lang groovy>def range = { s, e -> s == e ? "${s}," : s == e - 1 ? "${s},${e}," : "${s}-${e}," }
def compressList = { list ->
def sb, start, end
(sb, start, end) = [<<, list[0], list[0]]
for (i in list[1..-1]) {
(sb, start, end) = i == end + 1 ? [sb, start, i] : [sb << range(start, end), i, i]
}
(sb << range(start, end))[0..-2].toString()
}
def compressRanges = { expanded -> compressList(Eval.me('[' + expanded + ']')) }</lang>
Test: <lang groovy>def s =
0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39
println (compressRanges(s))</lang>
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39
Haskell
<lang haskell>import Data.List (intercalate)
extractRange :: [Int] -> String extractRange = intercalate "," . f
where f :: [Int] -> [String]
f (x1 : x2 : x3 : xs) | x1 + 1 == x2 && x2 + 1 == x3
= (show x1 ++ '-' : show xn) : f xs'
where (xn, xs') = g (x3 + 1) xs
g a (n : ns) | a == n = g (a + 1) ns
| otherwise = (a - 1, n : ns)
g a [] = (a - 1, [])
f (x : xs) = show x : f xs
f [] = []</lang>
<lang text>> extractRange $ [0..2] ++ 4 : [6..8] ++ 11 : 12 : [14..25] ++ [27..33] ++ [35..39] "0-2,4,6-8,11,12,14-25,27-33,35-39"</lang>
Icon and Unicon
<lang Icon>procedure main()
R := [ 0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39 ]
write("Input list := ",list2string(R))
write("Extracted sting := ",s := range_extract(R) | "FAILED")
end
procedure range_extract(R) #: return string/range representation of a list of unique integers local s,sep,low,high,x
every if integer(x:= !R) ~= x then fail # ensure all are integers, R := sort(set(R)) # unique, and sorted
s := sep := ""
while s ||:= sep || ( low := high := get(R) ) do { # lower bound of range
sep := ","
while high := ( R[1] = high + 1 ) do get(R) # find the end of range
if high > low+1 then s ||:= "-" || high # - record range of 3+
else if high = low+1 then push(R,high) # - range of 2, high becomes new low
}
return s
end
procedure list2string(L) #: helper to convert list to string local s
every (s := "[ ") ||:= !L || " " return s || "]"
end</lang> Sample output:
Input list := [ 0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39 ] Extracted sting := 0-2,4,6-8,11,12,14-25,27-33,35-39
J
<lang j>require 'strings' fmt=: [: ;@(8!:0) [`]`({. ; (',-' {~ 2 < #) ; {:)@.(2 <. #) group=: <@fmt;.1~ 1 ~: 0 , 2 -~/\ ] extractRange=: ',' joinstring group</lang>
Example use:
<lang j> extractRange 0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39 0-2,4,6-8,11,12,14-25,27-33,35-39</lang>
Java
<lang java>public class Range{ public static void main(String[] args){ System.out.println(compress2Range("-6, -3, -2, -1, 0, 1, 3, 4, 5, 7," + " 8, 9, 10, 11, 14, 15, 17, 18, 19, 20"));
System.out.println(compress2Range(
"0, 1, 2, 4, 6, 7, 8, 11, 12, 14, " +
"15, 16, 17, 18, 19, 20, 21, 22, 23, 24," +
"25, 27, 28, 29, 30, 31, 32, 33, 35, 36," +
"37, 38, 39"));
}
private static String compress2Range(String expanded){
StringBuilder result = new StringBuilder();
String[] nums = expanded.replace(" ", "").split(",");
int firstNum = Integer.parseInt(nums[0]);
int rangeSize = 0;
for(int i = 1; i < nums.length; i++){
int thisNum = Integer.parseInt(nums[i]);
if(thisNum - firstNum - rangeSize == 1){
rangeSize++;
}else{
if(rangeSize != 0){
result.append(firstNum).append((rangeSize == 1) ? ",": "-")
.append(firstNum+rangeSize).append(",");
rangeSize = 0;
}else{
result.append(firstNum).append(",");
}
firstNum = thisNum;
}
}
if(rangeSize != 0){
result.append(firstNum).append((rangeSize == 1) ? "," : "-").
append(firstNum + rangeSize);
rangeSize = 0;
} else {
result.append(firstNum);
}
return result.toString();
}
}</lang> Output:
-6,-3-1,3-5,7-11,14,15,17-20 0-2,4,6-8,11,12,14-25,27-33,35-39
JavaScript
<lang javascript>function rangeExtraction(list) {
var len = list.length; var out = []; var i, j;
for (i = 0; i < len; i = j + 1) {
// beginning of range or single
out.push(list[i]);
// find end of range
for (var j = i + 1; j < len && list[j] == list[j-1] + 1; j++);
j--;
if (i == j) {
// single number
out.push(",");
} else if (i + 1 == j) {
// two numbers
out.push(",", list[j], ",");
} else {
// range
out.push("-", list[j], ",");
}
}
out.pop(); // remove trailing comma
return out.join("");
}
// using print function as supplied by Rhino standalone print(rangeExtraction([
0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39
]));</lang>
K
<lang k>grp : {(&~1=0,-':x)_ x} fmt : {:[1=#s:$x;s;(*s),:[3>#s;",";"-"],*|s]} erng: {{x,",",y}/,//'fmt'grp x}</lang>
Example: <lang k> erng 0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39 "0-2,4,6-8,11,12,14-25,27-33,35-39"</lang>
Liberty BASIC
<lang lb> s$ = "0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24," + _
"25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39"
print ExtractRange$( s$) end
function ExtractRange$( range$)
n = 1
count = ItemCount( range$, ",")
while n <= count
startValue = val( word$( range$, n, ","))
m = n + 1
while m <= count
nextValue = val( word$( range$, m, ","))
if nextValue - startValue <> m - n then exit while
m = m + 1
wend
if m - n > 2 then
ExtractRange$ = ExtractRange$ + str$( startValue) + "-" + str$( startValue + m - n - 1) + ","
else
for i = n to m - 1
ExtractRange$ = ExtractRange$ + str$( startValue + i - n) + ","
next i
end if
n = m
wend
ExtractRange$ = left$( ExtractRange$, len( ExtractRange$) - 1)
end function
function ItemCount( list$, separator$)
while word$( list$, ItemCount + 1, separator$) <> ""
ItemCount = ItemCount + 1
wend
end function </lang> Sample output:- 0-2,4,6-8,11,12,14-25,27-33,35-39
MUMPS
<lang MUMPS>RANGCONT(X) ;Integer range contraction
NEW Y,I,CONT,NOTFIRST,CURR,PREV,NEXT,SEQ SET Y="",SEQ=0,PREV="",CONT=0 FOR I=1:1:$LENGTH(X,",") DO .SET NOTFIRST=$LENGTH(Y),CURR=$PIECE(X,",",I),NEXT=$PIECE(X,",",I+1) .FOR Q:$EXTRACT(CURR)'=" " S CURR=$EXTRACT(CURR,2,$LENGTH(CURR)) ;clean up leading spaces .S SEQ=((CURR-1)=PREV)&((CURR+1)=NEXT) .IF 'NOTFIRST SET Y=CURR .IF NOTFIRST DO ..;Order matters due to flags ..IF CONT&SEQ ;Do nothing ..IF 'CONT&'SEQ SET Y=Y_","_CURR ..IF CONT&'SEQ SET Y=Y_CURR,CONT=0 ..IF 'CONT&SEQ SET Y=Y_"-",CONT=1 .SET PREV=CURR IF CONT SET Y=Y_PREV K I,CONT,NOTFIRST,CURR,PREV,NEXT,SEQ QUIT Y</lang>
Example:
USER>SET S="0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39" USER>W $$RANGCONT^ROSETTA(S) 0-2,4,6-8,11,12,14-25,27-33,35-39
OCaml
<lang ocaml>let range_extract = function
| [] -> []
| x::xs ->
let f (i,j,ret) k =
if k = succ j then (i,k,ret) else (k,k,(i,j)::ret) in
let (m,n,ret) = List.fold_left f (x,x,[]) xs in
List.rev ((m,n)::ret)
let string_of_range rng =
let str (a,b) = if a = b then string_of_int a else Printf.sprintf "%d%c%d" a (if b = succ a then ',' else '-') b in String.concat "," (List.map str rng)
let () =
let li =
[ 0; 1; 2; 4; 6; 7; 8; 11; 12; 14; 15; 16; 17; 18; 19; 20; 21;
22; 23; 24; 25; 27; 28; 29; 30; 31; 32; 33; 35; 36; 37; 38; 39 ]
in
let rng = range_extract li in
print_endline(string_of_range rng)</lang>
Output
0-2,4,6-8,11,12,14-25,27-33,35-39
OxygenBasic
<lang oxygenbasic>
dim sys ints(100) ints=> 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39
function ShowRange(sys*i) as string
'==================================
pr=""
n=0
e=0
j=0
k=-1
do
j++
n=i(j)
e=i(j+1)
if e<j then
exit do
end if
if e=n+1 and i(j+2)=n+2 then 'LOOKAHEAD
if k=-1 then k=n
else
if k>=0 then
pr+=k "-" i(j+1) ", " 'RANGE OF VALUES
j++
k=-1
else
pr+=n ", " 'SINGLE VALUES
end if
end if
end do
return left pr, len(pr)-2
end function
print ShowRange ints
</lang>
Oz
<lang oz>declare
fun {Extract Xs}
{CommaSeparated
{Map {ExtractRanges Xs} RangeToString}}
end
fun {ExtractRanges Xs}
fun {Loop Ys Start End}
case Ys
of Y|Yr andthen Y == End+1 then {Loop Yr Start Y}
[] Y|Yr then Start#End|{Loop Yr Y Y}
[] nil then [Start#End]
end
end
in
case Xs
of X|Xr then {Loop Xr X X}
[] nil then nil
end
end
fun {RangeToString S#E}
if E-S >= 2 then
{VirtualString.toString S#"-"#E}
else
{CommaSeparated
{Map {List.number S E 1} Int.toString}}
end
end
fun {CommaSeparated Xs}
{Flatten {Intersperse "," Xs}}
end
fun {Intersperse Sep Xs}
case Xs of X|Y|Xr then
X|Sep|{Intersperse Sep Y|Xr}
else
Xs
end
end
in
{System.showInfo
{Extract [ 0 1 2 4 6 7 8 11 12 14
15 16 17 18 19 20 21 22 23 24
25 27 28 29 30 31 32 33 35 36
37 38 39 ]}}</lang>
Sample output: <lang oz>0-2,4,6-8,11,12,14-25,27-33,35-39</lang>
Perl
Using regexes. Also handles +/- and negative integer ranges.
<lang Perl>sub rangext {
my $str = join ' ', @_;
1 while $str =~ s{([+-]?\d+) ([+-]?\d+)}
{$1.(abs($2 - $1) == 1 ? '~' : ',').$2}eg; # abs for neg ranges
$str =~ s/(\d+)~(?:[+-]?\d+~)+([+-]?\d+)/$1-$2/g;
$str =~ tr/~/,/;
return $str;
}
- Test and display
my @test = qw(0 1 2 4 6 7 8 11 12 14,
15 16 17 18 19 20 21 22 23 24,
25 27 28 29 30 31 32 33 35 36,
37 38 39);
print rangext(@test), "\n";</lang>
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39
Perl 6
<lang Perl6>sub range-extraction (@integer-list) {
my $prev-term = [@integer-list.shift];
my @range-list;
for @integer-list -> $element {
if $element == $prev-term[*-1] + 1 {
$prev-term.push: $element;
}
else {
@range-list.push: $prev-term;
$prev-term = [$element];
}
}
@range-list.push: $prev-term;
@range-list.map({$^a.elems>2 ?? $a[0]~'-'~$a[*-1] !! $a.flat}).join(',');
}
say range-extraction(
(-6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20)
);
say range-extraction(
(0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39)
);</lang>
Output:
-6,-3-1,3-5,7-11,14,15,17-20 0-2,4,6-8,11,12,14-25,27-33,35-39
PicoLisp
<lang PicoLisp>(de rangeextract (Lst)
(glue ","
(make
(while Lst
(let (N (pop 'Lst) M N)
(while (= (inc M) (car Lst))
(setq M (pop 'Lst)) )
(cond
((= N M) (link N))
((= (inc N) M) (link N M))
(T (link (list N '- M))) ) ) ) ) ) )</lang>
Output:
: (rangeextract
(0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22
23 24 25 27 28 29 30 31 32 33 35 36 37 38 39 ) )
-> "0-2,4,6-8,11,12,14-25,27-33,35-39"
PL/I
<lang PL/I> /* Modified 19 November 2011 to meet requirement that there be at */ /* least 3 items in a run. */ range_extraction: /* 17 August 2010 */
procedure options (main); declare (c, d) character (1); declare (old, new, initial) fixed binary (31); declare in file; declare out file output;
open file (in) title ('/range2.dat,type(text),recsize(80)' );
open file (out) output title ('/range2.out,type(text),recsize(70)');
c = ' '; d = ',';
get file (in) list (old);
do forever;
initial = old;
on endfile (in) begin;
put file (out) edit (c, trim(old)) (a);
stop;
end;
get file (in) list (new);
if new = old+1 then
do; /* we have a run. */
on endfile (in) begin;
if old > initial+1 then d = '-';
put file (out) edit (c, trim(initial), d, trim(old) ) (a);
stop;
end;
do while (new = old+1);
old = new;
get file (in) list (new);
end;
/* At this point, old holds the last in a run; */
/* initial holds the first in a run. */
/* if there are only two members in a run, don't use the */
/* range notation. */
if old > initial+1 then d = '-';
put file (out) edit (c, trim(initial), d, trim(old) ) (a);
old = new;
end;
else /* we have an isolated value. */
do;
put file (out) edit (c, trim(old)) (a);
old = new;
end;
c, d = ',';
end;
end range_extraction; </lang> OUTPUT 17/8/2010: <lang>
0-2,4,6-8,11-12,14-25,27-33,35-39
</lang> OUTPUT 19/11/2011: <lang>
0-2,4,6-8,11,12,14-25,27-33,35-39
</lang>
Prolog
Works with SWI-Prolog and library clpfd.
The code uses three predicates extract_Range/2, study_Range/2 and pack_Range/2.
Every predicate works in both directions arg1 towards arg2 and arg2 towards arg1, so that Range extraction and Range expansion work with the same predicates but in reverse order.
<lang Prolog>range_extract :-
L = [0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39] ,
writeln(L),
pack_Range(L, LP),
maplist(study_Range, R, LP),
extract_Range(LA, R),
atom_chars(A, LA),
writeln(A).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% extract_Range(?In, ?Out)
% In : '-6,-3--1,3-5,7-11,14,15,17-20' =>
% Out : [-6], [-3--1], [3-5],[7-11], [14],[15], [17-20]
%
extract_Range([], []).
extract_Range(X , [Range | Y1]) :-
get_Range(X, U-U, Range, X1),
extract_Range(X1, Y1).
get_Range([], Range-[], Range, []). get_Range([','|B], Range-[], Range, B) :- !.
get_Range([A | B], EC, Range, R) :- append_dl(EC, [A | U]-U, NEC), get_Range(B, NEC, Range, R).
append_dl(X-Y, Y-Z, X-Z).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % study Range(?In, ?Out) % In : [-6] % Out : [-6,-6] % % In : [-3--1] % Out : [-3, -1] % study_Range(Range1, [Deb, Deb]) :-
catch(number_chars(Deb, Range1), Deb, false).
study_Range(Range1, [Deb, Fin]) :-
append(A, ['-'|B], Range1),
A \= [],
number_chars(Deb, A),
number_chars(Fin, B).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %
- - use_module(library(clpfd)).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % Pack Range(?In, ?Out) % In : -6, % Out : [-6] % % In : -3, -2,-1 % Out : [-3,-1] % pack_Range([],[]).
pack_Range([X|Rest],[[X | V]|Packed]):-
run(X,Rest, [X|V], RRest), pack_Range(RRest,Packed).
run(Fin,[Other|RRest], [Deb, Fin],[Other|RRest]):- Fin #\= Deb, Fin #\= Deb + 1, Other #\= Fin+1.
run(Fin,[],[_Var, Fin],[]).
run(Var,[Var1|LRest],[Deb, Fin], RRest):- Fin #\= Deb, Fin #\= Deb + 1, Var1 #= Var + 1, run(Var1,LRest,[Deb, Fin], RRest).
run(Val,[Other|RRest], [Val, Val],[Other|RRest]). </lang>
OutPut :
?- range_extract. [0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39] 0-2,4,6-8,11,12,14-25,27-33,35-39 true
PureBasic
Even though the example integer list only includes ascending ranges this code will also handles descending ranges. <lang PureBasic>DataSection
Data.i 33 ;count of elements to be read Data.i 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 Data.i 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39
EndDataSection
NewList values()
- setup list
Define elementCount, i Read.i elementCount For i = 1 To elementCount
AddElement(values()): Read.i values()
Next
Procedure.s rangeExtract(List values())
Protected listSize = ListSize(values()) - 1
Protected rangeMarker, rangeStart, rangeIncrement, retraceSteps, rangeSize, endOfRange, output.s, sub.s
ForEach values()
rangeStart = values():
sub = Str(rangeStart)
If NextElement(values())
retraceSteps = 1
rangeIncrement = values() - rangeStart
If rangeIncrement = 1 Or rangeIncrement = -1
;found start of possible range
If ListIndex(values()) <> listSize
retraceSteps = 2
rangeSize = 2
endOfRange = #False
rangeMarker = values()
While NextElement(values())
If values() - rangeMarker <> rangeIncrement
endOfRange = #True
Break
EndIf
rangeSize + 1
rangeMarker = values()
Wend
If rangeSize > 2
sub = Str(rangeStart) + "-" + Str(rangeMarker)
If Not endOfRange
retraceSteps = 0 ;at end of list
Else
retraceSteps = 1
EndIf
EndIf
EndIf
EndIf
;return to the value before look-aheads
While retraceSteps > 0
PreviousElement(values()): retraceSteps - 1
Wend
EndIf
output + sub + ","
Next
ProcedureReturn RTrim(output, ",")
EndProcedure
If OpenConsole()
PrintN(rangeExtract(values())) Print(#CRLF$ + #CRLF$ + "Press ENTER to exit") Input() CloseConsole()
EndIf</lang> Sample output:
0-2,4,6-8,11,12,14-25,27-33,35-39
Python
<lang python>def rangeextract(lst):
lenlst = len(lst)
i, ranges = 0, []
while i< lenlst:
low = lst[i]
while i <lenlst-1 and lst[i]+1 == lst[i+1]: i +=1
hi = lst[i]
ranges.append(
'%i-%i' % (low, hi) if hi - low >= 2 else
('%i,%i' % (low, hi) if hi - low == 1 else
'%i' % low) )
i += 1
return ','.join(ranges)
lst = [ 0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39]
print(rangeextract(lst))</lang>
Sample output
0-2,4,6-8,11,12,14-25,27-33,35-39
This idiomatic version uses generator functions to separate the algorithmic task of capturing ranges from the task of formatting the ranges.
<lang python>
def grouper(lst):
src = iter(lst)
acc = [ next(src) ]
for i in src:
if i == acc[-1] + 1: acc.append(i)
else:
yield acc
acc = [i]
yield acc
raise StopIteration()
def rangegrouper(lst):
for g in grouper(lst):
if len(g) == 2:
# satisfy rule that only runs longer than 2 are grouped
a,b = g
yield [a]
yield [b]
else: yield g
raise StopIteration()
input= [0, 1, 2, 4, 6, 7, 8, 11, 12, 14,15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36,37, 38, 39] print list(rangegrouper(input)) # print groups as_strings= ['%s%s%s' % ((g[0],'-',g[-1]) if len(g) > 1 else (g[0],,)) for g in rangegrouper(input)] print as_strings print ', '.join(as_strings) </lang> Output
[[0, 1, 2], [4], [6, 7, 8], [11], [12], [14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25], [27, 28, 29, 30, 31, 32, 33], [35, 36, 37, 38, 39]] ['0-2', '4', '6-8', '11', '12', '14-25', '27-33', '35-39'] 0-2, 4, 6-8, 11, 12, 14-25, 27-33, 35-39
Qi
<lang qi> (define make-range
Start Start -> ["," Start] Start End -> ["," Start "," End] where (= End (+ Start 1)) Start End -> ["," Start "-" End])
(define range-extract-0
Start End [] -> (make-range Start End) Start End [A|As] -> (range-extract-0 Start A As) where (= (+ 1 End) A) Start End [A|As] -> (append (make-range Start End) (range-extract-0 A A As)))
(define range-extract
[A |As] -> (FORMAT NIL "~{~a~}" (tail (range-extract-0 A A As))))
(range-extract [ 0 1 2 4 6 7 8 11 12 14
15 16 17 18 19 20 21 22 23 24
25 27 28 29 30 31 32 33 35 36
37 38 39])
</lang>
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39
REXX
<lang>/*REXX program to test range extraction. */ aaa='0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22',
'23 24 25 27 28 29 30 31 32 33 35 36 37 38 39'
say 'old='aaa; say /*show the old range of numbers. */ new= /*the new list (maybe with ranges)*/ w=words(aaa) /*number of numbers in the list. */
/*Note: index of DO (J) gets modified within loop !.*/ do j=1 to w /*step through num word in list.*/ _=word(aaa,j) /*get the Jth number in the list. */ new=new',' _ /*append Jth number to new list. */ inc=1 /*start with an increment of one. */
do k=j+1 to w /*now, search for end of range. */ __=word(aaa,k) /*get the Kth number in the list. */ if __\==_+inc then leave /*this number 1 greater than prev?*/ inc=inc+1 /*yes, then increase the range. */ g_=__ /*placeholder for last good number*/ end /*k*/
k=k-1 /*fudge the Kth word (subtract 1).*/ if k==j then iterate /*no range? Then keep truckin'.*/ if g_==_+1 then iterate /*range of 1? Then keep truckin'.*/ new=new'-'g_ /*indicate a range of numbers. */ j=k /*Bad practice!! Change DO index.*/ end /*j*/
new=substr(new,3) /*remove extraneous leading comma.*/ new=space(new,0) /*remove all spaces (blanks). */ say 'new='new /*display the new list of numbers.*/</lang> output (note that 11 and 12 are not considered a range):
old=0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39 new=0-2,4,6-8,11,12,14-25,27-33,35-39
Ruby
<lang ruby>def range_extract(l)
sorted = l.sort
range = []
start = sorted.first
# pad the list with a big value, so that the last loop iteration will
# appended something to the range
sorted.concat([Float::MAX]).each_cons(2) do |prev,n|
if prev.succ < n
if start == prev
range << start.to_s
else
range << "%d%s%d" % [start, (start.succ == prev ? "," : "-"), prev]
end
start = n
end
end
range.join(',')
end
lst = [
0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39
]
p rng = range_extract(lst)</lang>
output:
"0-2,4,6-8,11,12,14-25,27-33,35-39"
Scala
<lang scala>object Range {
def spanRange(ls:List[Int])={
var last=ls.head
ls span {x => val b=x<=last+1; last=x; b}
}
def toRangeList(ls:List[Int]):List[List[Int]]=ls match {
case Nil => List()
case _ => spanRange(ls) match {
case (range, Nil) => List(range)
case (range, rest) => range :: toRangeList(rest)
}
}
def toRangeString(ls:List[List[Int]])=ls map {r=>
if(r.size<3) r mkString ","
else r.head + "-" + r.last
} mkString ","
def main(args: Array[String]): Unit = {
var l=List(0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39)
println(toRangeString(toRangeList(l)))
}
}</lang>
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39
Scheme
<lang scheme> (define (make-range start end)
(cond ((= start end)
`("," ,start))
((= end (+ start 1))
`("," ,start "," ,end))
(else
`("," ,start "-" ,end))))
(define (range-extract-0 start end a)
(cond ((null? a)
(make-range start end))
((= (+ 1 end) (car a))
(range-extract-0 start (car a) (cdr a)))
(else
(append (make-range start end)
(range-extract-0 (car a) (car a) (cdr a))))))
(define (range-extract a)
(apply string-append (map (lambda (x)
(if (number? x)
(number->string x)
x))
(cdr (range-extract-0 (car a) (car a) (cdr a))))))
(range-extract '( 0 1 2 4 6 7 8 11 12 14
15 16 17 18 19 20 21 22 23 24
25 27 28 29 30 31 32 33 35 36
37 38 39))
</lang>
Outputs:
0-2,4,6-8,11,12,14-25,27-33,35-39
Seed7
<lang seed7>$ include "seed7_05.s7i";
const func string: rangeExtraction (in array integer: numbers) is func
result
var string: rangeStri is "";
local
var integer: index is 1;
var integer: index2 is 1;
begin
while index <= length(numbers) do
while index2 <= pred(length(numbers)) and numbers[succ(index2)] = succ(numbers[index2]) do
incr(index2);
end while;
if succ(index) < index2 then
rangeStri &:= "," <& numbers[index] <& "-" <& numbers[index2];
else
while index <= index2 do
rangeStri &:= "," <& numbers[index];
incr(index);
end while;
end if;
incr(index2);
index := index2;
end while;
rangeStri := rangeStri[2 ..];
end func;
const proc: main is func
begin
writeln(rangeExtraction([] (0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19,
20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39)));
end func;</lang>
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39
SNOBOL4
Handles +/- and negative ranges.
<lang SNOBOL4>* # Absolute value
define('abs(n)') :(abs_end)
abs abs = ~(abs = lt(n,0) -n) n :(return) abs_end
define('rangext(str)d1,d2') :(rangext_end)
rangext num = ('+' | '-' | ) span('0123456789') rxt1 str ',' span(' ') = ' ' :s(rxt1) rxt2 str num . d1 ' ' num . d2 = + d1 ('~,' ? *eq(abs(d2 - d1),1) '~' | ',') d2 :s(rxt2) rxt3 str ('~' | '-') num '~' = '-' :s(rxt3) rxt4 str '~' = ',' :s(rxt4)
rangext = str :(return)
rangext_end
- # Test and display
test = '0, 1, 2, 4, 6, 7, 8, 11, 12, 14, '
+ '15, 16, 17, 18, 19, 20, 21, 22, 23, 24, ' + '25, 27, 28, 29, 30, 31, 32, 33, 35, 36, ' + '37, 38, 39'
output = rangext(test)
end</lang>
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39
Tcl
<lang tcl>proc rangeExtract list {
set result [lindex $list 0]
set first [set last [lindex $list 0]]
foreach term [lrange $list 1 end] {
if {$term == $last+1} { set last $term continue } if {$last > $first} { append result [expr {$last == $first+1 ? "," : "-"}] $last } append result "," $term set first [set last $term]
}
if {$last == $first+1} {
append result "," $last
} elseif {$last > $first} {
append result "-" $last
} return $result
}
- Commas already removed so it is a natural Tcl list
puts [rangeExtract {
0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39
}]</lang> Output:
0-2,4,6-8,11,12,14-25,27-33,35-39
TUSCRIPT
TUSCRIPT has a built-in routine "COMBINE" that combines a range of integers by a dash '-'. It is possible to differ between every range that expands more than two values (6-8), and every range that expands less than two values (11,12 are not combined). <lang tuscript> $$ MODE TUSCRIPT MODE DATA $$ numbers=* 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39 $$ MODE TUSCRIPT numbers=EXCHANGE (numbers,":,><<> :':") unrangednrs=JOIN (numbers,"") rangednrs=COMBINE (unrangednrs,"") rangednrs=EXCHANGE (rangednrs,":':,:") PRINT rangednrs </lang> Output:
0-2,4,6-8,11,12,14-25,27-33,35-39
Solution without COMBINE <lang tuscript> $$ MODE TUSCRIPT MODE DATA $$ numbers=* 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39 $$ MODE TUSCRIPT numbers=EXCHANGE (numbers,":,><<> :':") unrangednrs=JOIN (numbers,"")
help = APPEND (unrangednrs, "999999999") rest = REMOVE (help, 1, n_1) n_2 = n_1, n_3= n_2 + 1,rangednrs= "" LOOP n= rest
IF (n!=n_3) THEN
rangednrs = APPEND (rangednrs, n_1)
IF (n_1!=n_2) THEN
range=n_1+1
IF (range==n_2) THEN
rangednrs = APPEND (rangednrs,n_2)
ELSE
rangednrs = CONCAT (rangednrs, "-", n_2)
ENDIF
ENDIF
n_1 = n
ENDIF
n_2 = n, n_3 = n_2 + 1
ENDLOOP rangednrs=EXCHANGE (rangednrs,":':,:") PRINT rangednrs
</lang> Output:
0-2,4,6-8,11,12,14-25,27-33,35-39
Ursala
<lang Ursala>#import std
- import int
x = <0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39>
f = mat`,+ ==?(~&l,^|T/~& :/`-)*bhPS+ %zP~~hzX*titZBPiNCSiNCQSL+ rlc ^|E/~& predecessor
- show+
t = <f x></lang>
output:
0-2,4,6-8,11,12,14-25,27-33,35-39
VBA
<lang vb> Public Function RangeExtraction(AList) As String 'AList is a variant that is an array, assumed filled with numbers in ascending order Const RangeDelim = "-" 'range delimiter Dim result As String Dim InRange As Boolean Dim Posn, ub, lb, rangestart, rangelen As Integer
result = "" 'find dimensions of AList ub = UBound(AList) lb = LBound(AList) Posn = lb While Posn < ub
rangestart = Posn
rangelen = 0
InRange = True
'try to extend the range
While InRange
rangelen = rangelen + 1
If Posn = ub Then
InRange = False
Else
InRange = (AList(Posn + 1) = AList(Posn) + 1)
Posn = Posn + 1
End If
Wend
If rangelen > 2 Then 'output the range if it has more than 2 elements
result = result & "," & Format$(AList(rangestart)) & RangeDelim & Format$(AList(rangestart + rangelen - 1))
Else 'output the separate elements
For i = rangestart To rangestart + rangelen - 1
result = result & "," & Format$(AList(i))
Next
End If
Posn = rangestart + rangelen
Wend RangeExtraction = Mid$(result, 2) 'get rid of first comma! End Function
Public Sub RangeTest()
'test function RangeExtraction
'first test with a Variant array
Dim MyList As Variant
MyList = Array(0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39)
Debug.Print "a) "; RangeExtraction(MyList)
'next test with an array of integers Dim MyOtherList(1 To 20) As Integer MyOtherList(1) = -6 MyOtherList(2) = -3 MyOtherList(3) = -2 MyOtherList(4) = -1 MyOtherList(5) = 0 MyOtherList(6) = 1 MyOtherList(7) = 3 MyOtherList(8) = 4 MyOtherList(9) = 5 MyOtherList(10) = 7 MyOtherList(11) = 8 MyOtherList(12) = 9 MyOtherList(13) = 10 MyOtherList(14) = 11 MyOtherList(15) = 14 MyOtherList(16) = 15 MyOtherList(17) = 17 MyOtherList(18) = 18 MyOtherList(19) = 19 MyOtherList(20) = 20 Debug.Print "b) "; RangeExtraction(MyOtherList) End Sub </lang>
Output:
RangeTest a) 0-2,4,6-8,11,12,14-25,27-33,35-39 b) -6,-3-1,3-5,7-11,14,15,17-20
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