Search a list
You are encouraged to solve this task according to the task description, using any language you may know.
Find the index of a string (needle) in an indexable, ordered collection of strings (haystack).
Raise an exception if the needle is missing.
If there is more than one occurrence then return the smallest index to the needle.
Return the largest index to a needle that has multiple occurrences in the haystack.
ACL2
<lang lisp>(defun index-of-r (e xs i)
(cond ((endp xs) nil)
((equal e (first xs)) i)
(t (index-of-r e (rest xs) (1+ i)))))
(defun index-of (e xs)
(index-of-r e xs 0))</lang>
ActionScript
Using the built-in Error class
<lang ActionScript>var list:Vector.<String> = Vector.<String>(["Zig", "Zag", "Wally", "Ronald", "Bush", "Krusty", "Charlie", "Bush", "Boz", "Zag"]); function lowIndex(listToSearch:Vector.<String>, searchString:String):int { var index:int = listToSearch.indexOf(searchString); if(index == -1) throw new Error("String not found: " + searchString); return index; }
function highIndex(listToSearch:Vector.<String>, searchString:String):int { var index:int = listToSearch.lastIndexOf(searchString); if(index == -1) throw new Error("String not found: " + searchString); return index; }</lang>
Using a custom error
In StringNotFoundError.as: <lang ActionScript>package { public class StringNotFoundError extends Error { public function StringNotFoundError(message:String) { super(message); } } }</lang> In a separate file: <lang ActionScript>import StringNotFoundError; var list:Vector.<String> = Vector.<String>(["Zig", "Zag", "Wally", "Ronald", "Bush", "Krusty", "Charlie", "Bush", "Boz", "Zag"]); function lowIndex(listToSearch:Vector.<String>, searchString:String):int { var index:int = listToSearch.indexOf(searchString); if(index == -1) throw new StringNotFoundError("String not found: " + searchString); return index; }
function highIndex(listToSearch:Vector.<String>, searchString:String):int { var index:int = listToSearch.lastIndexOf(searchString); if(index == -1) throw new StringNotFoundError("String not found: " + searchString); return index; } </lang>
Ada
<lang ada>with Ada.Strings.Unbounded; use Ada.Strings.Unbounded; with Ada.Text_IO; use Ada.Text_IO;
procedure Test_List_Index is
Not_In : exception;
type List is array (Positive range <>) of Unbounded_String;
function Index (Haystack : List; Needle : String) return Positive is
begin
for Index in Haystack'Range loop
if Haystack (Index) = Needle then
return Index;
end if;
end loop;
raise Not_In;
end Index;
-- Functions to create lists
function "+" (X, Y : String) return List is
begin
return (1 => To_Unbounded_String (X), 2 => To_Unbounded_String (Y));
end "+";
function "+" (X : List; Y : String) return List is
begin
return X & (1 => To_Unbounded_String (Y));
end "+";
Haystack : List := "Zig"+"Zag"+"Wally"+"Ronald"+"Bush"+"Krusty"+"Charlie"+"Bush"+"Bozo";
procedure Check (Needle : String) is
begin
Put (Needle);
Put_Line ("at" & Positive'Image (Index (Haystack, Needle)));
exception
when Not_In => Put_Line (" is not in");
end Check;
begin
Check ("Washington");
Check ("Bush");
end Test_List_Index;</lang>
- Output:
Washington is not in Bushat 5
Aime
<lang aime>integer search(list l, text s) {
integer i;
i = 0;
while (i < l_length(l)) {
if (!compare(l_q_text(l, i), s)) {
break;
}
i += 1;
}
if (i == l_length(l)) {
i = -1;
}
return i;
}
void search_for(list l, ...) {
integer i;
i = 1;
while (i < count()) {
integer index;
index = search(l, $i);
o_text($i);
if (index == -1) {
o_text(" is not in the haystack\n");
} else {
o_plan(" is at ", index, "\n");
}
i += 1; }
}
integer main(void) {
list l;
l = l_effect("Zig", "Zag", "Wally", "Ronald", "Bush", "Krusty",
"Charlie", "Bush", "Boz", "Zag");
search_for(l, "Bush", "Washington", "Zag");
return 0;
}</lang>
- Output:
Bush is at 4 Washington is not in the haystack Zag is at 1
ALGOL 68
Using a FORMAT "value error" exception
<lang algol68> FORMAT hay stack := $c("Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo")$;
FILE needle exception; STRING ref needle;
associate(needle exception, ref needle);
PROC index = (FORMAT haystack, REF STRING needle)INT:(
INT out;
ref needle := needle;
getf(needle exception,(haystack, out));
out
);
test:(
[]STRING needles = ("Washington","Bush");
FOR i TO UPB needles DO
STRING needle := needles[i];
on value error(needle exception, (REF FILE f)BOOL: value error);
printf(($d" "gl$,index(hay stack, needle), needle));
end on value error;
value error:
printf(($g" "gl$,needle, "is not in haystack"));
end on value error: reset(needle exception)
OD
)</lang>
- Output:
Washington is not in haystack 5 Bush
Using a manual FOR loop with no exception
<lang algol68> []STRING hay stack = ("Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo");
PROC index = ([]STRING hay stack, STRING needle)INT:(
INT index;
FOR i FROM LWB hay stack TO UPB hay stack DO
index := i;
IF hay stack[index] = needle THEN
found
FI
OD;
else:
LWB hay stack - 1
EXIT
found:
index
);
test:(
[]STRING needles = ("Washington","Bush");
FOR i TO UPB needles DO
STRING needle := needles[i];
INT result = index(hay stack, needle);
IF result >= LWB hay stack THEN
printf(($d" "gl$, result, needle))
ELSE
printf(($g" "gl$,needle, "is not in haystack"))
FI
OD
)</lang>
- Output:
Washington is not in haystack 5 Bush
AutoHotkey
<lang AutoHotkey>haystack = Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo needle = bush, washington Loop, Parse, needle, `, {
If InStr(haystack, A_LoopField) MsgBox, % A_LoopField Else MsgBox % A_LoopField . " not in haystack"
}</lang>
AWK
If we use an awk array indexed with "the order" of the string, to check if the needle is in the haystack we must walk the whole array; if we use the string itself as index (in awk index for an array is indeed an hash), and put its "index" (order number in the list) as associated value, we can fastly check if the needle is in the haystack. But we can't fastly use its order number to get the string value at that position.
In the following implementation we can reach the strings by numeric index with the array haystack_byorder (so, e.g. haystack_byorder[4] gives Bush), and know the "position" of the needle (if it exists) using it as string index for the array haystack, as example does. (Beware: this method does not work when there are duplicates!)
<lang awk>#! /usr/bin/awk -f BEGIN {
# create the array, using the word as index...
words="Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo";
split(words, haystack_byorder, " ");
j=0;
for(idx in haystack_byorder) {
haystack[haystack_byorder[idx]] = j; j++;
}
# now check for needle (we know it is there, so no "else")...
if ( "Bush" in haystack ) {
print "Bush is at " haystack["Bush"];
}
# check for unexisting needle
if ( "Washington" in haystack ) {
print "impossible";
} else {
print "Washington is not here";
}
}</lang>
BASIC
<lang qbasic>DATA foo, bar, baz, quux, quuux, quuuux, bazola, ztesch, foo, bar, thud, grunt DATA foo, bar, bletch, foo, bar, fum, fred, jim, sheila, barney, flarp, zxc DATA spqr, wombat, shme, foo, bar, baz, bongo, spam, eggs, snork, foo, bar DATA zot, blarg, wibble, toto, titi, tata, tutu, pippo, pluto, paperino, aap DATA noot, mies, oogle, foogle, boogle, zork, gork, bork
DIM haystack(54) AS STRING DIM needle AS STRING, found AS INTEGER, L0 AS INTEGER
FOR L0 = 0 TO 54
READ haystack(L0)
NEXT
DO
INPUT "Word to search for? (Leave blank to exit) ", needle
IF needle <> "" THEN
FOR L0 = 0 TO UBOUND(haystack)
IF UCASE$(haystack(L0)) = UCASE$(needle) THEN
found = 1
PRINT "Found "; CHR$(34); needle; CHR$(34); " at index "; LTRIM$(STR$(L0))
END IF
NEXT
IF found < 1 THEN
PRINT CHR$(34); needle; CHR$(34); " not found"
END IF
ELSE
EXIT DO
END IF
LOOP</lang>
- Output:
Word to search for? (Leave blank to exit) foo Found "foo" at index 0 Found "foo" at index 8 Found "foo" at index 12 Found "foo" at index 15 Found "foo" at index 27 Found "foo" at index 34 Word to search for? (Leave blank to exit) bar Found "bar" at index 1 Found "bar" at index 9 Found "bar" at index 13 Found "bar" at index 16 Found "bar" at index 28 Found "bar" at index 35 Word to search for? (Leave blank to exit) baz Found "baz" at index 2 Found "baz" at index 29 Word to search for? (Leave blank to exit)
Batch File
The index of this simple implementation is 1-based. The "haystack" data are borrowed from the BASIC implementation. <lang dos>@echo off setlocal enabledelayedexpansion
%==Sample list==% set "data=foo, bar, baz, quux, quuux, quuuux, bazola, ztesch, foo, bar, thud, grunt" set "data=%data% foo, bar, bletch, foo, bar, fum, fred, jim, sheila, barney, flarp, zxc" set "data=%data% spqr, wombat, shme, foo, bar, baz, bongo, spam, eggs, snork, foo, bar" set "data=%data% zot, blarg, wibble, toto, titi, tata, tutu, pippo, pluto, paperino, aap" set "data=%data% noot, mies, oogle, foogle, boogle, zork, gork, bork"
%==Sample "needles" [whitespace is the delimiter]==% set "needles=foo bar baz jim bong"
%==Counting and Seperating each Data==% set datalen=0 for %%. in (!data!) do ( set /a datalen+=1 set data!datalen!=%%. ) %==Do the search==% for %%A in (!needles!) do ( set "first=" set "last=" set "found=0" for /l %%B in (1,1,%datalen%) do ( if "!data%%B!" == "%%A" ( set /a found+=1 if !found! equ 1 set first=%%B set last=%%B ) )
if !found! equ 0 echo."%%A": Not found. if !found! equ 1 echo."%%A": Found once in index [!first!]. if !found! gtr 1 echo."%%A": Found !found! times. First instance:[!first!] Last instance:[!last!].
) %==We are done==% echo. pause</lang>
- Output:
"foo": Found 6 times. First instance:[1] Last instance:[35]. "bar": Found 6 times. First instance:[2] Last instance:[36]. "baz": Found 2 times. First instance:[3] Last instance:[30]. "jim": Found once in index [20]. "bong": Not found. Press any key to continue . . .
BBC BASIC
<lang bbcbasic> DIM haystack$(27)
haystack$() = "alpha","bravo","charlie","delta","echo","foxtrot","golf", \
\ "hotel","india","juliet","kilo","lima","mike","needle", \
\ "november","oscar","papa","quebec","romeo","sierra","tango", \
\ "needle","uniform","victor","whisky","x-ray","yankee","zulu"
needle$ = "needle"
maxindex% = DIM(haystack$(), 1)
FOR index% = 0 TO maxindex%
IF needle$ = haystack$(index%) EXIT FOR
NEXT
IF index% <= maxindex% THEN
PRINT "First found at index "; index%
FOR last% = maxindex% TO 0 STEP -1
IF needle$ = haystack$(last%) EXIT FOR
NEXT
IF last%<>index% PRINT "Last found at index "; last%
ELSE
ERROR 100, "Not found"
ENDIF</lang>
Bracmat
For both subtasks, pattern matching is used. The second subtasks proceeds in two steps. First, the first word that occurs twice is found (if it exists). Then, the last occurrence of this word is found using forced backtracking (see the ~ node) until failure.
<lang Bracmat>( return the largest index to a needle that has multiple
occurrences in the haystack and print the needle : ?list
& ( !list:? haystack [?index ?
& out$("The word 'haystack' occurs at 1-based index" !index)
| out$"The word 'haystack' does not occur"
)
& ( !list
: ? %@?needle ? !needle ?
: ( ? !needle [?index (?&~)
| ?
& out
$ ( str
$ ( "The word '"
!needle
"' occurs more than once. The last 1-based index is "
!index
)
)
)
| out$"No word occurs more than once."
)
);</lang>
- Output:
The word 'haystack' occurs at 1-based index 14 The word 'the' occurs more than once. The last 1-based index is 17
Burlesque
<lang burlesque>blsq ) {"Zig" "Zag" "Wally" "Bush" "Ronald" "Bush"}"Bush"Fi 3</lang>
If you want all indices:
<lang burlesque>blsq ) {"Zig" "Zag" "Wally" "Bush" "Ronald" "Bush"}{"Bush"==}fI {3 5}</lang>
C
<lang c>#include <stdio.h>
- include <string.h>
const char *haystack[] = {
"Zig", "Zag", "Wally", "Ronald", "Bush", "Krusty", "Charlie", "Bush", "Boz", "Zag", NULL
};
int search_needle(const char *needle, const char **hs) {
int i = 0;
while( hs[i] != NULL ) {
if ( strcmp(hs[i], needle) == 0 ) return i;
i++;
}
return -1;
}
int search_last_needle(const char *needle, const char **hs) {
int i, last=0;
i = last = search_needle(needle, hs);
if ( last < 0 ) return -1;
while( hs[++i] != NULL ) {
if ( strcmp(needle, hs[i]) == 0 ) {
last = i;
}
}
return last;
}
int main() {
printf("Bush is at %d\n", search_needle("Bush", haystack));
if ( search_needle("Washington", haystack) == -1 )
printf("Washington is not in the haystack\n");
printf("First index for Zag: %d\n", search_needle("Zag", haystack));
printf("Last index for Zag: %d\n", search_last_needle("Zag", haystack));
return 0;
}</lang>
- Output:
Bush is at 4 Washington is not in the haystack First index for Zag: 1 Last index for Zag: 9
C++
The following code shows three different ways to solve the task.
<lang cpp>#include <string>
- include <algorithm>
- include <iterator>
- include <cstddef>
- include <exception>
- include <iostream>
// an exception to throw (actually, throwing an exception in this case is generally considered bad style, but it's part of the task) class not_found: public std::exception { public:
not_found(std::string const& s): text(s + " not found") {}
char const* what() const throw() { return text.c_str(); }
~not_found() throw() {}
private:
std::string text;
};
// needle search function, C-style interface version using standard library std::size_t get_index(std::string* haystack, int haystack_size, std::string needle) {
std::size_t index = std::find(haystack, haystack+haystack_size, needle) - haystack; if (index == haystack_size) throw not_found(needle); else return index;
}
// needle search function, completely generic style, needs forward iterators // (works with any container, but inefficient if not random-access-iterator) template<typename FwdIter>
typename std::iterator_traits<FwdIter>::difference_type fwd_get_index(FwdIter first, FwdIter last, std::string needle)
{
FwdIter elem = std::find(first, last, needle); if (elem == last) throw not_found(needle); else return std::distance(first, elem);
}
// needle search function, implemented directly, needs only input iterator, works efficiently with all sequences template<typename InIter>
typename std::iterator_traits<InIter>::difference_type generic_get_index(InIter first, InIter last, std::string needle)
{
typename std::iterator_traits<InIter>::difference_type index = 0;
while (first != last && *first != needle)
{
++index;
++first;
}
if (first == last)
throw not_found(needle);
else
return index;
}
// ----------------------------------------------------------------------------------------------------------------------------------
// a sample haystack (content copied from Haskell example) std::string haystack[] = { "Zig", "Zag", "Wally", "Ronald", "Bush", "Krusty", "Charlie", "Bush", "Bozo" };
// some useful helper functions template<typename T, std::size_t sz> T* begin(T (&array)[sz]) { return array; } template<typename T, std::size_t sz> T* end(T (&array)[sz]) { return array + sz; } template<typename T, std::size_t sz> std::size_t size(T (&array)[sz]) { return sz; }
// test function searching a given needle with each of the methods void test(std::string const& needle) {
std::cout << "-- C style interface --\n";
try
{
std::size_t index = get_index(haystack, size(haystack), needle);
std::cout << needle << " found at index " << index << "\n";
}
catch(std::exception& exc) // better catch standard exceptions as well; me might e.g. run out of memory
{
std::cout << exc.what() << "\n";
}
std::cout << "-- generic interface, first version --\n";
try
{
std::size_t index = fwd_get_index(begin(haystack), end(haystack), needle);
std::cout << needle << " found at index " << index << "\n";
}
catch(std::exception& exc) // better catch standard exceptions as well; me might e.g. run out of memory
{
std::cout << exc.what() << "\n";
}
std::cout << "-- generic interface, second version --\n";
try
{
std::size_t index = generic_get_index(begin(haystack), end(haystack), needle);
std::cout << needle << " found at index " << index << "\n";
}
catch(std::exception& exc) // better catch standard exceptions as well; me might e.g. run out of memory
{
std::cout << exc.what() << "\n";
}
}
int main() {
std::cout << "\n=== Word which only occurs once ===\n";
test("Wally");
std::cout << "\n=== Word occuring multiple times ===\n";
test("Bush");
std::cout << "\n=== Word not occuring at all ===\n";
test("Goofy");
}</lang>
- Output:
(note that in C++, indices start at 0)
=== Word which only occurs once === -- C style interface -- Wally found at index 2 -- generic interface, first version -- Wally found at index 2 -- generic interface, second version -- Wally found at index 2 === Word occuring multiple times === -- C style interface -- Bush found at index 4 -- generic interface, first version -- Bush found at index 4 -- generic interface, second version -- Bush found at index 4 === Word not occuring at all === -- C style interface -- Goofy not found -- generic interface, first version -- Goofy not found -- generic interface, second version -- Goofy not found
C++11
<lang cpp>/* new c++-11 features
* list class * initialization strings * auto typing * lambda functions * noexcept * find * for/in loop */
- include <iostream> // std::cout, std::endl
- include <algorithm> // std::find
- include <list> // std::list
- include <vector> // std::vector
- include <string> // string::basic_string
using namespace std; // saves typing of "std::" before everything
int main() {
// initialization lists // create objects and fully initialize them with given values
list<string> l { "Zig", "Zag", "Wally", "Homer", "Madge",
"Watson", "Ronald", "Bush", "Krusty", "Charlie",
"Bush", "Bush", "Boz", "Zag" };
list<string> n { "Bush" , "Obama", "Homer", "Sherlock" };
// lambda function with auto typing // auto is easier to write than looking up the compicated // specialized iterator type that is actually returned. // Just know that it returns an iterator for the list at the position found, // or throws an exception if s in not in the list. // runtime_error is used because it can be initialized with a message string.
auto contains = [](list<string> l, string s) throw(runtime_error)
{
auto r = find(begin(l), end(l), s );
if ( r == end(l) ) throw runtime_error( s + " not found" );
return r; };
// returns an int vector with the indexes of the search string
// The & is a "default capture" meaning that it "allows in"
// the variables that are in scope where it is called by their
// name to simplify things.
auto index = [&](list<string> l, string s) noexcept
{
vector<int> index_v;
int idx = 0;
for(auto& r : l)
{ if ( s.compare(r) == 0 ) index_v.push_back(idx); // match -- add to vector idx++; }
// even though index_v is local to the lambda function,
// c++11 move semantics does what you want and returns it
// live and intact instead of destroying it or returning a copy.
// (very efficient for large objects!)
return index_v;
};
// for/in loop
for (const string& s : n) // new iteration syntax is simple and intuitive
{
try
{
auto cont = contains( l , s); // checks if there is any match
vector<int> vf = index( l, s );
cout << "l contains: " << s << " at " ;
for (auto x : vf) { cout << x << " "; } // if vector is empty this doesn't run
cout << endl ;
}
catch (const runtime_error& r) // string not found
{ cout << r.what() << endl; continue; // try next string }
} //for
return 0;
} // main
/* end */</lang>
- Output:
l contains: Bush at 7 10 11 Obama not found l contains: Homer at 3 Sherlock not found
C#
<lang csharp>using System; using System.Collections.Generic;
class Program {
static void Main(string[] args) {
List<string> haystack = new List<string>() { "Zig", "Zag", "Wally", "Ronald", "Bush", "Krusty", "Charlie", "Bush", "Bozo" };
foreach (string needle in new string[] { "Washington", "Bush" }) {
int index = haystack.IndexOf(needle);
if (index < 0) Console.WriteLine("{0} is not in haystack",needle);
else Console.WriteLine("{0} {1}",index,needle);
}
}
}</lang>
Ceylon
<lang ceylon>shared test void searchAListTask() {
value haystack = [
"Zig", "Zag", "Wally", "Ronald", "Bush",
"Krusty", "Charlie", "Bush", "Bozo"];
assert(exists firstIdx = haystack.firstOccurrence("Bush"));
assert(exists lastIdx = haystack.lastOccurrence("Bush"));
assertEquals(firstIdx, 4); assertEquals(lastIdx, 7);
}</lang>
Clojure
<lang clojure>(let [haystack ["Zig" "Zag" "Wally" "Ronald" "Bush" "Krusty" "Charlie" "Bush" "Bozo"]]
(let [idx (.indexOf haystack "Zig")]
(if (neg? idx)
(throw (Error. "item not found."))
idx)))</lang>
Extra credit: Since Clojure vectors implement java.util.List, you can switch .indexOf for .lastIndexOf to find the highest index of your value.
COBOL
<lang cobol>*> This is written to COBOL85, which does not include exceptions.
IDENTIFICATION DIVISION.
PROGRAM-ID. Search-List.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 haystack-area.
78 Haystack-Size VALUE 10.
03 haystack-data.
05 FILLER PIC X(7) VALUE "Zig".
05 FILLER PIC X(7) VALUE "Zag".
05 FILLER PIC X(7) VALUE "Wally".
05 FILLER PIC X(7) VALUE "Ronald".
05 FILLER PIC X(7) VALUE "Bush".
05 FILLER PIC X(7) VALUE "Krusty".
05 FILLER PIC X(7) VALUE "Charlie".
05 FILLER PIC X(7) VALUE "Bush".
05 FILLER PIC X(7) VALUE "Boz".
05 FILLER PIC X(7) VALUE "Zag".
03 haystack-table REDEFINES haystack-data.
05 haystack PIC X(7) OCCURS Haystack-Size TIMES
INDEXED BY haystack-index.
01 needle PIC X(7).
PROCEDURE DIVISION.
main.
MOVE "Bush" TO needle
PERFORM find-needle
MOVE "Goofy" TO needle
PERFORM find-needle
- *> Extra task
MOVE "Bush" TO needle
PERFORM find-last-of-needle
GOBACK
.
find-needle.
SEARCH haystack
AT END
DISPLAY needle " not found."
WHEN haystack (haystack-index) = needle
DISPLAY "Found " needle " at " haystack-index "."
END-SEARCH
.
find-last-of-needle.
PERFORM VARYING haystack-index FROM Haystack-Size BY -1
UNTIL haystack-index = 0
OR haystack (haystack-index) = needle
END-PERFORM
IF haystack-index = 0
DISPLAY needle " not found."
ELSE
DISPLAY "Found last of " needle " at " haystack-index "."
END-IF
.</lang>
- Output:
Found Bush at +000000005. Goofy not found. Found last of Bush at +000000008.
Common Lisp
<lang lisp>(let ((haystack '(Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo)))
(dolist (needle '(Washington Bush))
(let ((index (position needle haystack)))
(if index
(progn (print index) (princ needle))
(progn (print needle) (princ "is not in haystack"))))))</lang>
- Output:
WASHINGTON is not in haystack 4 BUSH
The position function solves this task elegantly. <lang lisp> CL-USER> (defparameter *list* '(Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo))
- LIST*
CL-USER> (position 'Bush *list*) 4 CL-USER> (position 'Bush *list* :from-end t) 7 CL-USER> (position 'Washington *list*) NIL</lang>
D
<lang d>import std.algorithm, std.range, std.string;
auto firstIndex(R, T)(R hay, T needle) {
auto i = countUntil(hay, needle);
if (i == -1)
throw new Exception("No needle found in haystack");
return i;
}
auto lastIndex(R, T)(R hay, T needle) {
return walkLength(hay) - firstIndex(retro(hay), needle) - 1;
}
void main() {
auto h = split("Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo");
assert(firstIndex(h, "Bush") == 4);
assert(lastIndex(h, "Bush") == 7);
}</lang>
Delphi
<lang Delphi>program Needle;
{$APPTYPE CONSOLE}
uses
SysUtils, Classes;
var
list: TStringList; needle: string; ind: Integer;
begin
list := TStringList.Create;
try
list.Append('triangle');
list.Append('fork');
list.Append('limit');
list.Append('baby');
list.Append('needle');
list.Sort;
needle := 'needle';
ind := list.IndexOf(needle);
if ind < 0 then
raise Exception.Create('Needle not found')
else begin
Writeln(ind);
Writeln(list[ind]);
end;
Readln; finally list.Free; end;
end.</lang>
- Output:
3 needle
DWScript
<lang Delphi>var haystack : array of String = ["Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo"];
function Find(what : String) : Integer; begin
Result := haystack.IndexOf(what);
if Result < 0 then
raise Exception.Create('not found');
end;
PrintLn(Find("Ronald")); // 3 PrintLn(Find('McDonald')); // exception</lang>
E
<lang e>def haystack := ["Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo"]
/** meet the 'raise an exception' requirement */ def find(needle) {
switch (haystack.indexOf1(needle)) {
match ==(-1) { throw("an exception") }
match index { return index }
}
}
println(find("Ronald")) # prints 3 println(find("McDonald")) # will throw</lang>
Elena
<lang elena>#import system'routines.
- import extensions.
program = [
var haystack := ("Zig", "Zag", "Wally", "Ronald", "Bush", "Krusty", "Charlie", "Bush", "Bozo").
("Washington", "Bush") run &each: needle
[
var index := haystack indexOfElement:needle.
if (index == -1)
[ console writeLine:needle:" is not in haystack". ];
[ console writeLine:index:" ":needle. ].
].
].</lang>
Elixir
<lang elixir>haystack = ~w(Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo)
Enum.each(~w(Bush Washington), fn needle ->
index = Enum.find_index(haystack, fn x -> x==needle end)
if index, do: (IO.puts "#{index} #{needle}"),
else: raise "#{needle} is not in haystack\n"
end)</lang>
- Output:
4 Bush
** (RuntimeError) Washington is not in haystack
search.exs:5: anonymous fn/1 in :elixir_compiler_0.__FILE__/1
(elixir) lib/enum.ex:537: Enum."-each/2-lists^foreach/1-0-"/2
(elixir) lib/enum.ex:537: Enum.each/2
(elixir) lib/code.ex:316: Code.require_file/2
Erlang
Erlang lists can be accessed with the function lists:nth/2, which starts at 1 (first element). As such Erlang can be considered 1-indexed for this problem. Note that you could set the indexing to 0 by modifying the function call in pos/2. <lang erlang>-module(index). -export([main/0]).
main() ->
Haystack = ["Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo"],
Needles = ["Washington","Bush"],
lists:foreach(fun ?MODULE:print/1, [{N,pos(N, Haystack)} || N <- Needles]).
pos(Needle, Haystack) -> pos(Needle, Haystack, 1). pos(_, [], _) -> undefined; pos(Needle, [Needle|_], Pos) -> Pos; pos(Needle, [_|Haystack], Pos) -> pos(Needle, Haystack, Pos+1).
print({Needle, undefined}) -> io:format("~s is not in haystack.~n",[Needle]); print({Needle, Pos}) -> io:format("~s at position ~p.~n",[Needle,Pos]).</lang>
- Output:
Washington is not in haystack. Bush at position 5.
Euphoria
The find_all function from the standard library's search.e does nearly all the needed work here.There may be other ways to do this using Euphoria's various sequence searching functions as part of the standard library (std/search.e) and/or built into the language. The procedure can be made into a function to search with other strings, take user input and give output of the searched haystack.
<lang euphoria> include std/search.e include std/console.e
--the string "needle" and example haystacks to test the procedure sequence searchStr1 = "needle" sequence haystack1 = { "needle", "needle", "noodle", "node", "need", "needle ", "needle" } sequence haystack2 = {"spoon", "fork", "hay", "knife", "needle", "barn", "etcetera", "more hay", "needle", "a cow", "farmer", "needle", "dirt"} sequence haystack3 = {"needle"} sequence haystack4 = {"no", "need le s", "in", "this", "haystack"} sequence haystack5 = {"knee", "needle", "dull", "needle"} sequence haystack6 = {}
--search procedure with console output procedure haystackSearch(sequence hStack)
sequence foundNeedles = find_all(searchStr1, hStack)
puts(1,"---------------------------------\r\n")
if object(foundNeedles) and length(foundNeedles) > 0 then
printf(1, "First needle found at index %d \r\n", foundNeedles[1])
if length(foundNeedles) > 1 then
printf(1, "Last needle found at index %d \r\n", foundNeedles[length(foundNeedles)] )
for i = 1 to length(foundNeedles) do
printf(1, "Needle #%d ", i)
printf(1, "was at index %d .\r\n", foundNeedles[i])
end for
else
puts(1, "There was only one needle found in this haystack. \r\n")
end if
else
puts(1, "Simulated exception - No needles found in this haystack.\r\n")
end if
end procedure
--runs the procedure on all haystacks haystackSearch(haystack1) haystackSearch(haystack2) haystackSearch(haystack3) haystackSearch(haystack4) haystackSearch(haystack5) haystackSearch(haystack6) --wait for user to press a key to exit any_key() </lang>
- Output:
--------------------------------- First needle found at index 1 Last needle found at index 7 Needle #1 was at index 1 . Needle #2 was at index 2 . Needle #3 was at index 7 . --------------------------------- First needle found at index 5 Last needle found at index 12 Needle #1 was at index 5 . Needle #2 was at index 9 . Needle #3 was at index 12 . --------------------------------- First needle found at index 1 There was only one needle found in this haystack. --------------------------------- Simulated exception - No needles found in this haystack. --------------------------------- First needle found at index 2 Last needle found at index 4 Needle #1 was at index 2 . Needle #2 was at index 4 . --------------------------------- Simulated exception - No needles found in this haystack. Press Any Key to continue...
F#
<lang fsharp>List.findIndex (fun x -> x = "bar") ["foo"; "bar"; "baz"; "bar"] // -> 1
// A System.Collections.Generic.KeyNotFoundException
// is raised, if the predicate does not evaluate to
// true for any list element.</lang>
Factor
<lang factor>: find-index ( seq elt -- i )
'[ _ = ] find drop [ "Not found" throw ] unless* ; inline
- find-last-index ( seq elt -- i )
'[ _ = ] find-last drop [ "Not found" throw ] unless* ; inline</lang>
( scratchpad ) { "a" "b" "c" "d" "c" } "c" find-index .
2
( scratchpad ) { "a" "b" "c" "d" "c" } "c" find-last-index .
4
Forth
<lang forth>include lib/row.4th
create haystack
," Zig" ," Zag" ," Wally" ," Ronald" ," Bush" ," Krusty" ," Charlie" ," Bush" ," Boz" ," Zag" NULL ,
does>
dup >r 1 string-key row 2>r type 2r> ." is " if r> - ." at " . else r> drop drop ." not found" then cr
s" Washington" haystack s" Bush" haystack</lang>
Works with any ANS Forth
Needs the FMS-SI (single inheritance) library code located here: http://soton.mpeforth.com/flag/fms/index.html <lang forth>include FMS-SI.f include FMS-SILib.f
${ Dishonest Fake Left Karl Hillary Monica Bubba Hillary Multi-Millionaire } constant haystack
- needleIndex { addr len $list | cnt -- idx }
0 to cnt $list uneach: begin $list each: while @: addr len compare 0= if cnt exit then cnt 1+ to cnt repeat true abort" Not found" ;
- LastIndexOf { addr len $list | cnt last-found -- idx }
0 to cnt 0 to last-found $list uneach: begin $list each: while @: addr len compare 0= if cnt to last-found then cnt 1+ to cnt repeat last-found if last-found else true abort" Not found" then ;
s" Hillary" haystack needleIndex . \ => 4 s" Hillary" haystack LastIndexOf . \ => 7 s" Washington" haystack needleIndex . \ => aborted: Not found </lang>
Fortran
<lang fortran>program main
implicit none
character(len=7),dimension(10) :: haystack = [ & 'Zig ',& 'Zag ',& 'Wally ',& 'Ronald ',& 'Bush ',& 'Krusty ',& 'Charlie',& 'Bush ',& 'Boz ',& 'Zag ']
call find_needle('Charlie')
call find_needle('Bush')
contains
subroutine find_needle(needle) implicit none character(len=*),intent(in) :: needle integer :: i do i=1,size(haystack) if (needle==haystack(i)) then write(*,'(A,I4)') trim(needle)//' found at index:',i return end if end do write(*,'(A)') 'Error: '//trim(needle)//' not found.' end subroutine find_needle
end program main</lang>
FreeBASIC
FreeBASIC doesn't have exceptions so we use a different approach to check if the needle is present or not in the haystack: <lang freebasic>' FB 1.05.0 Win64
Function tryFindString(s() As String, search As String, ByRef index As Integer) As Boolean
Dim length As Integer = UBound(s) - LBound(s) + 1
If length = 0 Then
index = LBound(s) - 1 outside array
Return False
End If
For i As Integer = LBound(s) To UBound(s)
If s(i) = search Then
index = i first occurrence
Return True
End If
Next
index = LBound(s) - 1 outside array
Return False
End Function
Function tryFindLastString(s() As String, search As String, ByRef index As Integer) As Boolean
Dim length As Integer = UBound(s) - LBound(s) + 1
If length = 0 Then
index = LBound(s) - 1 outside array
Return False
End If
Dim maxIndex As Integer = LBound(s) - 1 outside array
For i As Integer = LBound(s) To UBound(s)
If s(i) = search Then
maxIndex = i
End If
Next
If maxIndex > LBound(s) - 1 Then
index = maxIndex last occurrence
Return True
Else
Return False
End If
End Function
Dim haystack(1 To 9) As String = {"Zig", "Zag", "Wally", "Ronald", "Bush", "Krusty", "Charlie", "Bush", "Bozo"} Dim needle(1 To 4) As String = {"Zag", "Krusty", "Washington", "Bush"}
Dim As Integer index Dim As Boolean found For i As Integer = 1 To 4
found = tryFindString(haystack(), needle(i), index) If found Then Print needle(i); " found first at index"; index Else Print needle(i); " is not present" End If
Next found = tryFindLastString(haystack(), needle(4), index) If found Then
Print needle(4); " found last at index"; index
Else
Print needle(4); " is not present"
End If Print Print "Press any key to quit" Sleep</lang>
- Output:
Zag found first at index 2 Krusty found first at index 6 Washington is not present Bush found first at index 5 Bush found last at index 8
GAP
<lang gap># First position is built-in haystack := Eratosthenes(10000);; needle := 8999;; Position(haystack, needle);
- 1117
LastPosition := function(L, x)
local old, new;
old := 0;
new := 0;
while new <> fail do
new := Position(L, x, old);
if new <> fail then
old := new;
fi;
od;
return old;
end;
a := Shuffle(List([1 .. 100], x -> x mod 10));
- [ 0, 2, 4, 5, 3, 1, 0, 4, 8, 8, 2, 7, 6, 3, 3, 6, 4, 4, 3, 0, 7, 1, 8, 7, 2, 4, 7, 9, 4, 9, 4, 5, 9, 9, 6, 7, 8, 2, 3,
- 5, 1, 5, 4, 2, 0, 9, 6, 1, 1, 2, 2, 0, 5, 7, 6, 8, 8, 3, 1, 9, 5, 1, 9, 6, 8, 9, 2, 0, 6, 2, 1, 6, 1, 1, 2, 5, 3, 3,
- 0, 3, 5, 7, 5, 4, 6, 8, 0, 9, 8, 3, 7, 8, 0, 4, 9, 7, 0, 6, 5, 7 ]
Position(a, 0);
- 1
LastPosition(a, 0);
- 97</lang>
See also Eratosthenes and Shuffle functions in RosettaCode.
Go
Data used by both examples below. (You can give multiple files to go run, like $ go run data.go example.go) <lang go>package main
var haystack = []string{"Zig", "Zag", "Wally", "Ronald", "Bush", "Krusty",
"Charlie", "Bush", "Bozo", "Zag", "mouse", "hat", "cup", "deodorant", "television", "soap", "methamphetamine", "severed cat heads", "foo", "bar", "baz", "quux", "quuux", "quuuux", "bazola", "ztesch", "foo", "bar", "thud", "grunt", "foo", "bar", "bletch", "foo", "bar", "fum", "fred", "jim", "sheila", "barney", "flarp", "zxc", "spqr", ";wombat", "shme", "foo", "bar", "baz", "bongo", "spam", "eggs", "snork", "foo", "bar", "zot", "blarg", "wibble", "toto", "titi", "tata", "tutu", "pippo", "pluto", "paperino", "aap", "noot", "mies", "oogle", "foogle", "boogle", "zork", "gork", "bork", "sodium", "phosphorous", "californium", "copernicium", "gold", "thallium", "carbon", "silver", "gold", "copper", "helium", "sulfur"}</lang>
Linear search
<lang go>package main
import "fmt"
func main() {
// first task
printSearchForward("soap")
printSearchForward("gold")
printSearchForward("fire")
// extra task
printSearchReverseMult("soap")
printSearchReverseMult("gold")
printSearchReverseMult("fire")
}
// First task solution uses panic as an exception-like mechanism, as requested // by the task. Note however, this is not idiomatic in Go and in fact // is considered bad practice. func printSearchForward(s string) {
fmt.Printf("Forward search: %s: ", s)
defer func() {
if x := recover(); x != nil {
if err, ok := x.(string); ok && err == "no match" {
fmt.Println(err)
return
}
panic(x)
}
}()
fmt.Println("smallest index =", searchForwardPanic(s))
}
func searchForwardPanic(s string) int {
for i, h := range haystack {
if h == s {
return i
}
}
panic("no match")
return -1
}
// Extra task, a quirky search for multiple occurrences. This is written // without panic, and shows more acceptable Go programming practice. func printSearchReverseMult(s string) {
fmt.Printf("Reverse search for multiples: %s: ", s)
if i := searchReverseMult(s); i > -1 {
fmt.Println("largest index =", i)
} else {
fmt.Println("no multiple occurrence")
}
}
func searchReverseMult(s string) int {
largest := -1
for i := len(haystack) - 1; i >= 0; i-- {
switch {
case haystack[i] != s:
case largest == -1:
largest = i
default:
return largest
}
}
return -1
}</lang>
- Output:
Forward search: soap: smallest index = 15 Forward search: gold: smallest index = 77 Forward search: fire: no match Reverse search for multiples: soap: no multiple occurrence Reverse search for multiples: gold: largest index = 81 Reverse search for multiples: fire: no multiple occurrence
Map lookup
More efficient, if you're doing lots of lookups, is to build a map. This example doesn't completely conform to the task but gives the idea that you could store indexes as map values. <lang go>package main
import "fmt"
func main() {
m := map[string][]int{}
for i, needle := range haystack {
m[needle] = append(m[needle], i)
}
for _, n := range []string{"soap", "gold", "fire"} {
fmt.Println(n, m[n])
}
}</lang>
- Output:
soap [15] gold [77 81] fire []
Groovy
<lang groovy>def haystack = ["Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo"] def needles = ["Washington","Bush","Wally"] needles.each { needle ->
def index = haystack.indexOf(needle)
def lastindex = haystack.lastIndexOf(needle)
if (index < 0) {
assert lastindex < 0
println needle + " is not in haystack"
} else {
println "First index: " + index + " " + needle
println "Last index: " + lastindex + " " + needle
}
}</lang>
- Output:
Washington is not in haystack First index: 4 Bush Last index: 7 Bush First index: 2 Wally Last index: 2 Wally
Haskell
Libraries and data: <lang haskell>import Data.List
haystack=["Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo"] needles = ["Washington","Bush"]</lang> I use 'lambda' notation for readability.
- Find 'just' an index:
<lang haskell>*Main> map (\x -> (x,elemIndex x haystack)) needles [("Washington",Nothing),("Bush",Just 4)]</lang> Want to know if there are there more Bushes hiding in the haystack? <lang haskell>*Main> map (\x -> (x,elemIndices x haystack)) needles [("Washington",[]),("Bush",[4,7])]</lang> To be complete. Here is the 'point free' version of the task: <lang haskell>import Control.Monad import Control.Arrow
- Main> map (ap (,) (flip elemIndex haystack)) needles
[("Washington",Nothing),("Bush",Just 4)]</lang>
HicEst
<lang HicEst>CHARACTER haystack='Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo.' CHARACTER needle*10
DLG(TItle="Enter search string", Edit=needle)
n = EDIT(Text=haystack, Option=2, End, Count=needle) ! Option = word
IF( n == 0 ) THEN
WRITE(Messagebox="!") needle, "not found" ! bus not found
ELSE
first = EDIT(Text=needle, LeXicon=haystack) WRITE(ClipBoard) "First ", needle, "found in position ", first ! First bush found in position 5
last = EDIT(Text=haystack, End, Left=needle, Count=" ") + 1 WRITE(ClipBoard) "Last ", needle, "found in position ", last ! Last bush found in position 8
ENDIF</lang>
Icon and Unicon
<lang Icon> link lists
procedure main() haystack := ["Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo"] # the haystack every needle := !["Bush","Washington"] do { # the needles
if i := lindex(haystack,needle) then { # first occurrence
write("needle=",needle, " is at position ",i," in haystack.")
if i <:= last(lindex,[haystack,needle]) then # last occurrence
write("needle=",needle, " is at last position ",i," in haystack.")
}
else {
write("needle=",needle, " is not in haystack.")
runerr(500,needle) # throw an error
}
}
end
procedure last(p,arglist) #: return the last generation of p(arglist) or fail local i every i := p!arglist return \i end</lang>
Taken from the public domain Icon Programming Library's lindex in lists which generates list indices for x of any type <lang Icon>procedure lindex(lst, x) #: generate indices for items matching x
local i
every i := 1 to *lst do
if lst[i] === x then suspend i
end</lang>
- Output:
needle=Bush is at position 5 in haystack. needle=Bush is at last position 8 in haystack. needle=Washington is not in haystack. Run-time error 500 File haystack.icn; Line 7 program malfunction offending value: "Washington" Traceback: main(list_1 = []) runerr(500,"Washington") from line 7 in haystack.icn
Io
List has a indexOf method which does not raise an exception on lookup failure but returns nil therefore I extend List with a firstIndex method that does raise an exception. I also create a lastIndex extension that finds the last index of a matching object by iterating in reverse over the list. Note that all these methods find any object not just strings.
<lang Io>NotFound := Exception clone List firstIndex := method(obj,
indexOf(obj) ifNil(NotFound raise)
) List lastIndex := method(obj,
reverseForeach(i,v,
if(v == obj, return i)
)
NotFound raise
)
haystack := list("Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo") list("Washington","Bush") foreach(needle,
try(
write("firstIndex(\"",needle,"\"): ")
writeln(haystack firstIndex(needle))
)catch(NotFound,
writeln(needle," is not in haystack")
)pass
try(
write("lastIndex(\"",needle,"\"): ")
writeln(haystack lastIndex(needle))
)catch(NotFound,
writeln(needle," is not in haystack")
)pass
)</lang>
- Output:
firstIndex("Washington"): Washington is not in haystack
lastIndex("Washington"): Washington is not in haystack
firstIndex("Bush"): 4
lastIndex("Bush"): 7
J
J has a general and optimized lookup function, i.
For example:
<lang j> Haystack =: ;:'Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo'
Needles =: ;:'Washington Bush' Haystack i. Needles NB. first positions
9 4
Haystack i: Needles NB. last positions
9 7</lang>
Note that the arguments to i. can be anything (ie either or both may be scalars, lists, multidimensional arrays, etc).
To format output similar to the other examples, one might write:
<lang j> Haystack ;:^:_1@(] ,. [ ((<'is not in haystack')"_)`(#@[ I.@:= ])`(8!:0@])} i.) Needles Washington is not in haystack Bush 4</lang>
Or broken up into components and defined as a verb/function for finding the last positions: <lang j> msg=: (<'is not in haystack')"_ NB. not found message
idxmissing=: #@[ I.@:= ] NB. indices of items not found fmtdata=: 8!:0@] NB. format atoms as boxed strings findLastIndex=: ;:inv@(] ,. [ msg`idxmissing`fmtdata} i:)
Haystack findLastIndex Needles NB. usage
Washington is not in haystack Bush 7</lang>
To elaborate a bit: Array-oriented languages (like J) consume the input and produce the output in toto.
That is, all the results are produced simultaneously; consequently, throwing an exception for any part of the input would prohibit producing any output at all.
And while it is both possible and simple to treat the input item by item, this is significantly slower and loses the great advantage of array processing.
Therefore these languages generally produce a special, but conforming, output for "bad" inputs (in this case, an index past the end of the list). Then the functions which consume these outputs may be left untouched (as the special outputs are already in their domain) or may be extended simply.
In this case, there is only one function which formats and prints the results, and its treatment of "good" and "bad" outputs is identical (it cannot distinguish the two). It is simply that the outputs of previous functions have been arranged such that the results are conformable.
Java
for Lists, they have an indexOf() method: <lang java>import java.util.List; import java.util.Arrays;
List<String> haystack = Arrays.asList("Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo");
for (String needle : new String[]{"Washington","Bush"}) {
int index = haystack.indexOf(needle);
if (index < 0)
System.out.println(needle + " is not in haystack");
else
System.out.println(index + " " + needle);
}</lang>
for arrays, you have to do it manually: <lang java>import java.util.Arrays;
String[] haystack = { "Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo"};
for (String needle : new String[]{"Washington","Bush"}) {
int index = Arrays.binarySearch(haystack, needle);
if (index < 0)
System.out.println(needle + " is not in haystack");
else
System.out.println(index + " " + needle);
}</lang>
- Output:
Washington is not in haystack 4 Bush
JavaScript
<lang javascript>var haystack = ['Zig', 'Zag', 'Wally', 'Ronald', 'Bush', 'Krusty', 'Charlie', 'Bush', 'Bozo'] var needles = ['Bush', 'Washington']
for (var i in needles) {
var found = false;
for (var j in haystack) {
if (haystack[j] == needles[i]) {
found = true;
break;
}
}
if (found)
print(needles[i] + " appears at index " + j + " in the haystack");
else
throw needles[i] + " does not appear in the haystack"
}</lang>
The following
:
<lang javascript>for each (var needle in needles) {
var idx = haystack.indexOf(needle);
if (idx == -1)
throw needle + " does not appear in the haystack"
else
print(needle + " appears at index " + idx + " in the haystack");
}
// extra credit
for each (var elem in haystack) {
var first_idx = haystack.indexOf(elem);
var last_idx = haystack.lastIndexOf(elem);
if (last_idx > first_idx) {
print(elem + " last appears at index " + last_idx + " in the haystack");
break
}
}</lang>
Or, generalising enough (in ES5) to allow for varying definitions of the type of match we are looking for:
<lang JavaScript>(function () {
function findIndex(fnPredicate, list) {
for (var i = 0, lng = list.length; i < lng; i++) {
if (fnPredicate(list[i])) {
return i;
}
}
return Error("not found");
};
// DEFINING A PARTICULAR TYPE OF SEARCH MATCH
function matchCaseInsensitive(s, t) {
return s.toLowerCase() === t.toLowerCase();
}
var lstHaystack = [ 'Zig', 'Zag', 'Wally', 'Ronald', 'Bush', 'Krusty', 'Charlie', 'Bush', 'Bozo' ], lstReversed = lstHaystack.slice(0).reverse(), iLast = lstHaystack.length - 1, lstNeedles = ['bush', 'washington'];
return {
'first': lstNeedles.map(function (s) {
return [s, findIndex(function (t) {
return matchCaseInsensitive(s, t);
},
lstHaystack)];
}),
'last': lstNeedles.map(function (s) {
var varIndex = findIndex(function (t) {
return matchCaseInsensitive(s, t);
},
lstReversed);
return [
s,
typeof varIndex === 'number' ?
iLast - varIndex : varIndex
];
})
}
})();</lang>
Output:
<lang JavaScript>{
"first": [
[
"bush",
4
],
[
"washington",
"Error: not found"
]
],
"last": [
[
"bush",
7
],
[
"washington",
"Error: not found"
]
]
}</lang>
jq
The jq index origin is 0. The relevant methods for the tasks at hand are index/1 and indices/1.
In the following, the output is shown after the "# =>": <lang jq> ["a","b","c"] | index("b")
- => 1
["a","b","c","b"] | index("b")
- => 1
["a","b","c","b"]
| index("x") as $ix
| if $ix then $ix else error("element not found") end
- => jq: error: element not found
- Extra task - the last element of an array can be retrieved
- using -1 as an index:
["a","b","c","b","d"] | indices("b")[-1]
- => 3</lang>
Julia
<lang julia>julia> findfirst(x -> x=="yes", {"no","?","yes","maybe","yes"}) 3 julia> indexin({"yes"},{"no","?","yes","maybe","yes"}) 1-element Array{Int64,1}:
5
julia> findin({"no","?","yes","maybe","yes"},{"yes"}) 2-element Array{Int64,1}:
3 5
julia> find(x -> x=="yes", {"no","?","yes","maybe","yes"}) 2-element Array{Int64,1}:
3 5</lang>
K
<lang K> Haystack:("Zig";"Zag";"Wally";"Ronald";"Bush";"Krusty";"Charlie";"Bush";"Bozo")
Needles:("Washington";"Bush")
{:[y _in x;(y;x _bin y);(y;"Not Found")]}[Haystack]'Needles </lang>
- Output:
<lang K>(("Washington"
"Not Found")
("Bush"
4))</lang>
Additional: If more than one occurrence ("Bush"), also show position of the last occurrence. Here we use the dyadic verb _sm (string match) instead of _bin (binary search).
<lang K> Haystack2: Haystack,,"Bush"
Needles2:Needles,,"Zag"
{+(x;{:[#&x;,/?(*&x;*|&x);"Not found"]}'+x _sm/:y)}[Needles2;Haystack2]</lang>
- Output:
<lang K>(("Washington"
"Not found")
("Bush"
4 9)
("Zag"
1))</lang>
Kotlin
<lang scala>// version 1.0.6 (search_list.kt)
fun main(args: Array<String>) {
val haystack = listOf("Zig", "Zag", "Wally", "Ronald", "Bush", "Krusty", "Charlie", "Bush", "Boz", "Zag")
println(haystack)
var needle = "Zag"
var index = haystack.indexOf(needle)
val index2 = haystack.lastIndexOf(needle)
println("\n'$needle' first occurs at index $index of the list")
println("'$needle' last occurs at index $index2 of the list\n")
needle = "Donald"
index = haystack.indexOf(needle)
if (index == -1) throw Exception("$needle does not occur in the list")
} </lang>
- Output:
[Zig, Zag, Wally, Ronald, Bush, Krusty, Charlie, Bush, Boz, Zag]
'Zag' first occurs at index 1 of the list
'Zag' last occurs at index 9 of the list
Exception in thread "main" java.lang.Exception: Donald does not occur in the list
at Search_listKt.main(search_list.kt:13)
Lang5
<lang lang5>: haystack(*) ['rosetta 'code 'search 'a 'list 'lang5 'code] find-index ;
- find-index
2dup eq length iota swap select swap drop length if swap drop else drop " is not in haystack" 2 compress "" join then ;
- ==>search apply ;
['hello 'code] 'haystack ==>search .</lang>
- Output:
[ hello is not in haystack [ 1 6 ] ]
Lasso
Lasso arrays have a findindex method which returns all matching indexes. [1]
<lang Lasso>local(haystack) = array('Zig', 'Zag', 'Wally', 'Ronald', 'Bush', 'Krusty', 'Charlie', 'Bush', 'Bozo')
- haystack->findindex('Bush')->first // 5
- haystack->findindex('Bush')->last // 8
protect => {^
handle_error => {^ error_msg ^}
fail_if(not #haystack->findindex('Washington')->first,'Washington is not in haystack.')
^}</lang>
- Output:
5 8 Washington is not in haystack.
Liberty BASIC
<lang lb>haystack$="apple orange pear cherry melon peach banana needle blueberry mango strawberry needle " haystack$=haystack$+"pineapple grape kiwi blackberry plum raspberry needle cranberry apricot"
idx=1 do until word$(haystack$,idx)="" idx=idx+1 loop total=idx-1
needle$="needle" 'index of first occurrence for i = 1 to total
if word$(haystack$,i)=needle$ then exit for
next print needle$;" first found at index ";i
'index of last occurrence for j = total to 1
if word$(haystack$,j)=needle$ then exit for
next print needle$;" last found at index ";j if i<>j then
print "Multiple instances of ";needle$ else print "Only one instance of ";needle$;" in list."
end if
'raise exception needle$="cauliflower" for k=1 to total
if word$(haystack$,k)=needle$ then exit for
next if k>total then
print needle$;" not found in list."
else
print needle$;" found at index ";k
end if</lang>
Lingo
<lang lingo>haystack = ["apples", "oranges", "bananas", "oranges"] needle = "oranges"
pos = haystack.getPos(needle) if pos then
put "needle found at index "&pos
else
put "needle not found in haystack"
end if
-- "needle found at index 2"</lang>
Lisaac
<lang Lisaac>+ haystack : ARRAY[STRING]; haystack := "Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo".split; "Washington Bush".split.foreach { needle : STRING;
haystack.has(needle).if {
haystack.first_index_of(needle).print;
' '.print;
needle.print;
'\n'.print;
} else {
needle.print;
" is not in haystack\n".print;
};
};</lang>
Logo
<lang logo>to indexof :item :list
if empty? :list [(throw "NOTFOUND 0)] if equal? :item first :list [output 1] output 1 + indexof :item butfirst :list
end
to showindex :item :list
make "i catch "NOTFOUND [indexof :item :list] ifelse :i = 0 [(print :item [ not found in ] :list)] [(print :item [ found at position ] :i [ in ] :list)]
end
showindex "dog [My dog has fleas] ; dog found at position 2 in My dog has fleas showindex "cat [My dog has fleas] ; cat not found in My dog has fleas</lang>
Lua
<lang lua>list = {"mouse", "hat", "cup", "deodorant", "television", "soap", "methamphetamine", "severed cat heads"} --contents of my desk
item = io.read()
for i,v in ipairs(list)
if v == item then print(i) end
end</lang>
Mathematica
This examples shows you the first appearance, the last appearance, and all appearances (as a list): <lang Mathematica>haystack = {"Zig","Zag","Wally","Ronald","Bush","Zig","Zag","Krusty","Charlie","Bush","Bozo"}; needle = "Zag"; first = Position[haystack,needle,1]1,1 last = Position[haystack,needle,1]-1,1 all = Position[haystack,needle,1]All,1</lang> gives back: <lang Mathematica>2 7 {2,7}</lang>
MATLAB
Collections of strings are stored in cell arrays in MATLAB. The solution bellow will only work for a cell array of this construction:<lang MATLAB>stringCollection = {'string1','string2',...,'stringN'}</lang> It will not work for any other construction, for example:<lang MATLAB>stringCollection = {{'string1'},{'string2'},{...},{'stringN'}}</lang>
searchCollection.m: <lang MATLAB>function index = searchCollection(list,searchItem,firstLast)
%firstLast is a string containing either 'first' or 'last'. The 'first' %flag will cause searchCollection to return the index of the first %instance of the item being searched. 'last' will cause %searchCollection to return the index of the last instance of the item %being searched. indicies = cellfun(@(x)x==searchItem,list); index = find(indicies,1,firstLast); assert(~isempty(index),['The string searchItem does not exist in this collection of strings.']);
end</lang>
- Output:
<lang MATLAB>>> list = {'a','b','c','d','e','c','f','c'}; >> searchCollection(list,'c','first')
ans =
3
>> searchCollection(list,'c','last')
ans =
8
>> searchCollection(list,'g','last') ??? Error using ==> searchCollection at 11 The string 'g' does not exist in this collection of strings.</lang>
MAXScript
<lang maxscript>haystack=#("Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo")
for needle in #("Washington","Bush") do (
index = findItem haystack needle
if index == 0 then
(
format "% is not in haystack\n" needle
)
else
(
format "% %\n" index needle
)
)</lang>
- Output:
<lang maxscript>Washington is not in haystack 5 Bush</lang>
Maxima
<lang maxima>haystack: ["Zig","Zag","Wally","Ronald","Bush","Zig","Zag","Krusty","Charlie","Bush","Bozo"]; needle: "Zag";
findneedle(needle, haystack, [opt]):=block([idx],
idx: sublist_indices(haystack, lambda([w], w=needle)),
if emptyp(idx) then throw('notfound),
if emptyp(opt) then return(idx),
opt: first(opt),
if opt='f then first(idx) else if opt='l then last(idx) else throw('unknownmode));</lang>
- Usage:
(%i32) catch(findneedle("Zag", haystack, 'f));
(%o32) 2
(%i33) catch(findneedle("Zag", haystack, 'l));
(%o33) 7
(%i34) catch(findneedle("Washington", haystack));
(%o34) notfound
(%i35) catch(findneedle("Bush", haystack, 'f));
(%o35) 5
(%i36) catch(findneedle("Zag", haystack));
(%o36) [2, 7]
(%i37) catch(findneedle("Zag", haystack, 'l));
(%o37) 7
NetRexx
<lang NetRexx>/* NetRexx */ options replace format comments java crossref symbols nobinary
driver(arg) -- call the test wrapper return
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ method searchListOfWords(haystack, needle, forwards = (1 == 1), respectCase = (1 == 1)) public static signals Exception
if \respectCase then do
needle = needle.upper()
haystack = haystack.upper()
end
if forwards then wp = haystack.wordpos(needle)
else wp = haystack.words() - haystack.reverse().wordpos(needle.reverse()) + 1
if wp = 0 then signal Exception('*** Error! "'needle'" not found in list ***')
return wp
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ method searchIndexedList(haystack, needle, forwards = (1 == 1), respectCase = (1 == 1)) public static signals Exception
if forwards then do strtIx = 1 endIx = haystack[0] incrIx = 1 end else do strtIx = haystack[0] endIx = 1 incrIx = -1 end
wp = 0
loop ix = strtIx to endIx by incrIx
if respectCase then
if needle == haystack[ix] then wp = ix
else nop
else
if needle.upper() == haystack[ix].upper() then wp = ix
else nop
if wp > 0 then leave ix
end ix
if wp = 0 then signal Exception('*** Error! "'needle'" not found in indexed list ***')
return wp
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -- Test wrapper method driver(arg) public static
-- some manifests
TRUE_ = (1 == 1); FALSE_ = \TRUE_
FORWARDS_ = TRUE_; BACKWARDS_ = FALSE_
CASERESPECT_ = TRUE_; CASEIGNORE_ = \CASERESPECT_
-- test data
needles = ['barley', 'quinoa']
-- a simple list of words. Lists of words are indexable in NetRexx via the word(N) function
hayrick = 'Barley maize barley sorghum millet wheat rice rye barley Barley oats flax'
-- a Rexx indexed string made up from the words in hayrick
cornstook =
loop w_ = 1 to hayrick.words() -- populate the indexed string
cornstook[0] = w_
cornstook[w_] = hayrick.word(w_)
end w_
loop needle over needles
do -- process the list of words
say 'Searching for "'needle'" in the list "'hayrick'"'
idxF = searchListOfWords(hayrick, needle)
idxL = searchListOfWords(hayrick, needle, BACKWARDS_)
say ' The first occurence of "'needle'" is at index' idxF 'in the list'
say ' The last occurence of "'needle'" is at index' idxL 'in the list'
idxF = searchListOfWords(hayrick, needle, FORWARDS_, CASEIGNORE_)
idxL = searchListOfWords(hayrick, needle, BACKWARDS_, CASEIGNORE_)
say ' The first caseless occurence of "'needle'" is at index' idxF 'in the list'
say ' The last caseless occurence of "'needle'" is at index' idxL 'in the list'
say
catch ex = Exception
say ' 'ex.getMessage()
say
end
do -- process the indexed list
corn =
loop ci = 1 to cornstook[0]
corn = corn cornstook[ci]
end ci
say 'Searching for "'needle'" in the indexed list "'corn.space()'"'
idxF = searchIndexedList(cornstook, needle)
idxL = searchIndexedList(cornstook, needle, BACKWARDS_)
say ' The first occurence of "'needle'" is at index' idxF 'in the indexed list'
say ' The last occurence of "'needle'" is at index' idxL 'in the indexed list'
idxF = searchIndexedList(cornstook, needle, FORWARDS_, CASEIGNORE_)
idxL = searchIndexedList(cornstook, needle, BACKWARDS_, CASEIGNORE_)
say ' The first caseless occurence of "'needle'" is at index' idxF 'in the indexed list'
say ' The last caseless occurence of "'needle'" is at index' idxL 'in the indexed list'
say
catch ex = Exception
say ' 'ex.getMessage()
say
end
end needle
return</lang>
- Output:
Searching for "barley" in the list "Barley maize barley sorghum millet wheat rice rye barley Barley oats flax" The first occurence of "barley" is at index 3 in the list The last occurence of "barley" is at index 9 in the list The first caseless occurence of "barley" is at index 1 in the list The last caseless occurence of "barley" is at index 10 in the list Searching for "barley" in the indexed list "Barley maize barley sorghum millet wheat rice rye barley Barley oats flax" The first occurence of "barley" is at index 3 in the indexed list The last occurence of "barley" is at index 9 in the indexed list The first caseless occurence of "barley" is at index 1 in the indexed list The last caseless occurence of "barley" is at index 10 in the indexed list Searching for "quinoa" in the list "Barley maize barley sorghum millet wheat rice rye barley Barley oats flax" *** Error! "quinoa" not found in list *** Searching for "quinoa" in the indexed list "Barley maize barley sorghum millet wheat rice rye barley Barley oats flax" *** Error! "quinoa" not found in indexed list ***
Nim
<lang nim>let haystack = ["Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo"]
for needle in ["Bush", "Washington"]:
let f = haystack.find(needle) if f >= 0: echo f, " ", needle else: raise newException(ValueError, needle & " not in haystack")</lang>
Objective-C
<lang objc>NSArray *haystack = @[@"Zig",@"Zag",@"Wally",@"Ronald",@"Bush",@"Krusty",@"Charlie",@"Bush",@"Bozo"]; for (id needle in @[@"Washington",@"Bush"]) {
int index = [haystack indexOfObject:needle];
if (index == NSNotFound)
NSLog(@"%@ is not in haystack", needle);
else
NSLog(@"%i %@", index, needle);
}</lang>
Objeck
<lang objeck>use Structure;
bundle Default {
class Test {
function : Main(args : String[]) ~ Nil {
haystack := ["Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo"];
values := CompareVector->New();
each(i : haystack) {
values->AddBack(haystack[i]->As(Compare));
};
needles := ["Washington", "Bush"];
each(i : needles) {
values->Has(needles[i]->As(Compare))->PrintLine();
};
}
}
}</lang>
OCaml
<lang ocaml># let find_index pred lst =
let rec loop n = function
[] -> raise Not_found
| x::xs -> if pred x then n
else loop (n+1) xs
in
loop 0 lst;;
val find_index : ('a -> bool) -> 'a list -> int = <fun>
- let haystack =
["Zig";"Zag";"Wally";"Ronald";"Bush";"Krusty";"Charlie";"Bush";"Bozo"];;
val haystack : string list =
["Zig"; "Zag"; "Wally"; "Ronald"; "Bush"; "Krusty"; "Charlie"; "Bush"; "Bozo"]
- List.iter (fun needle ->
try
Printf.printf "%i %s\n" (find_index ((=) needle) haystack) needle
with Not_found ->
Printf.printf "%s is not in haystack\n" needle)
["Washington"; "Bush"];;
Washington is not in haystack 4 Bush - : unit = ()</lang>
Oforth
indexOf returns null if an object is not into a collection, not an exception.
<lang Oforth>: needleIndex(needle, haystack)
haystack indexOf(needle) dup ifNull: [ drop ExRuntime throw("Not found", needle) ] ;
[ "Zig", "Zag", "Wally", "Ronald", "Bush", "Krusty", "Charlie", "Bush", "Boz" ] const: Haystack
needleIndex("Bush", Haystack) println Haystack lastIndexOf("Bush") println needleIndex("Washington", Haystack) println</lang>
- Output:
5 8 [1:interpreter] ExRuntime : Not found <Washington>
ooRexx
All ooRexx collections support an index method that will search for an item. For ordered collections, this will always be the first item. For unordered collections, the index returned is undetermined. <lang ooRexx>-- ordered collections always return the first hit a = .array~of(1,2,3,4,4,5) say a~index(4) a2 = .array~new(5,5) -- multidimensional a2[3,3] = 4 -- the returned index is an array of values say a2~index(4)~makestring('line', ',') -- Note, list indexes are assigned when an item is added and -- are not tied to relative position l = .list~of(1,2,3,4,4,5) say l~index(4) q = .queue~of(1,2,3,4,4,5) say q~index(4) -- directories are unordered, so it is -- undertermined which one is returned d = .directory~new d["foo"] = 4 d["bar"] = 4 say d~index(4)</lang>
Oz
No such function exists for the built-in list type (the operation is quite inefficient, after all). A possible implementation: <lang oz>declare
%% Lazy list of indices of Y in Xs.
fun {Indices Y Xs}
for
X in Xs
I in 1;I+1
yield:Yield
do
if Y == X then {Yield I} end
end
end
fun {Index Y Xs}
case {Indices Y Xs} of X|_ then X
else raise index(elementNotFound Y) end
end
end
Haystack = ["Zig" "Zag" "Wally" "Ronald" "Bush" "Krusty" "Charlie" "Bush" "Bozo"]
in
{Show {Index "Bush" Haystack}}
{Show {List.last {Indices "Bush" Haystack}}}
{Show {Index "Washington" Haystack}} %% throws</lang>
PARI/GP
<lang parigp>find(v,n)={
my(i=setsearch(v,n));
if(i,
while(i>1, if(v[i-1]==n,i--))
,
error("Could not find")
);
i
};</lang>
Pascal
See Delphi
Perl
<lang perl>use List::Util qw(first);
my @haystack = qw(Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo);
foreach my $needle (qw(Washington Bush)) {
my $index = first { $haystack[$_] eq $needle } (0 .. $#haystack); # note that "eq" was used because we are comparing strings
# you would use "==" for numbers
if (defined $index) {
print "$index $needle\n";
} else {
print "$needle is not in haystack\n";
}
}</lang>
- Output:
Washington is not in haystack 4 Bush
You could install a non-standard module List::MoreUtils: <lang perl>use List::MoreUtils qw(first_index);
my @haystack = qw(Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo);
foreach my $needle (qw(Washington Bush)) {
my $index = first_index { $_ eq $needle } @haystack; # note that "eq" was used because we are comparing strings
# you would use "==" for numbers
if (defined $index) {
print "$index $needle\n";
} else {
print "$needle is not in haystack\n";
}
}</lang>
Alternatively, if you need to do this a lot, you could create a hash table mapping values to indices in the haystack: <lang perl>my @haystack = qw(Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo);
my %haystack_indices; @haystack_indices{ @haystack } = (0 .. $#haystack); # Caution: this finds the largest index, not the smallest
foreach my $needle (qw(Washington Bush)) {
my $index = $haystack_indices{$needle};
if (defined $index) {
print "$index $needle\n";
} else {
print "$needle is not in haystack\n";
}
}</lang>
- Output:
Washington is not in haystack 7 Bush
Perl 6
<lang perl6>my @haystack = <Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo>;
for <Washington Bush> -> $needle {
say "$needle -- { @haystack.first($needle, :k) // 'not in haystack' }";
}</lang>
- Output:
Washington -- not in haystack Bush -- 4
Or, including the "extra credit" task:
<lang perl6>my Str @haystack = <Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo>;
for <Washingston Bush> -> $needle {
my $first = @haystack.first($needle, :k);
if defined $first {
my $last = @haystack.first($needle, :k, :end);
say "$needle -- first at $first, last at $last";
}
else {
say "$needle -- not in haystack";
}
}</lang>
- Output:
Washingston -- not in haystack Bush -- first at 4, last at 7
The built-in method .first takes a smart-matcher, and returns the first matching list element.
The :k adverb tells it to return the key (a.k.a. list index) instead of the value of the matching element.
The :end adverb tells it to start searching from the end of the list.
If you plan to do many searches on the same large list, you might want to build a search hash first for efficient look-up:
<lang perl6>my @haystack = <Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo>;
my %index; %index{.value} //= .key for @haystack.pairs;
for <Washington Bush> -> $needle {
say "$needle -- { %index{$needle} // 'not in haystack' }";
}</lang>
Phix
<lang Phix>constant s = {"Zig", "Zag", "Wally", "Ronald", "Bush", "Krusty", "Charlie", "Bush", "Boz", "Zag"}
integer r = find("Zag",s) ?r -- 2 (first) r = find("Zag",s,r+1) ?r -- 10 (next) r = find("Zag",s,r+1) ?r -- 0 (no more) r = rfind("Zag",s) ?r -- 10 (last) r = find("Zog",s) ?r -- 0 (none)</lang>
PHP
<lang php>$haystack = array("Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo");
foreach (array("Washington","Bush") as $needle) {
$i = array_search($needle, $haystack); if ($i === FALSE) // note: 0 is also considered false in PHP, so you need to specifically check for FALSE echo "$needle is not in haystack\n"; else echo "$i $needle\n";
}</lang>
- Output:
Washington is not in haystack 4 Bush
PicoLisp
Note that in PicoLisp all indexes are one-based (the first element has the position '1') <lang PicoLisp>(de lastIndex (Item Lst)
(- (length Lst) (index Item (reverse Lst)) -1) )
(de findNeedle (Fun Sym Lst)
(prinl Sym " " (or (Fun Sym Lst) "not found")) )
(let Lst '(Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo)
(findNeedle index 'Washington Lst) (findNeedle index 'Bush Lst) (findNeedle lastIndex 'Bush Lst) )</lang>
- Output:
Washington not found Bush 5 Bush 8
PL/I
<lang pli>search: procedure () returns (fixed binary);
declare haystack (0:9) character (200) varying static initial
('apple', 'banana', 'celery', 'dumpling', 'egg', 'flour',
'grape', 'pomegranate', 'raisin', 'sugar' );
declare needle character (200) varying;
declare i fixed binary;
declare missing_needle condition;
on condition(missing_needle) begin;
put skip list ('your string || needle ||
does not exist in the haystack.');
end;
put ('Please type a string');
get edit (needle) (L);
do i = lbound(haystack,1) to hbound(haystack,1);
if needle = haystack(i) then return (i);
end;
signal condition(missing_needle);
return (lbound(haystack,1)-1);
end search;</lang>
PowerBASIC
<lang powerbasic>FUNCTION PBMAIN () AS LONG
DIM haystack(54) AS STRING
ARRAY ASSIGN haystack() = "foo", "bar", "baz", "quux", "quuux", "quuuux", _
"bazola", "ztesch", "foo", "bar", "thud", "grunt", "foo", _
"bar", "bletch", "foo", "bar", "fum", "fred", "jim", _
"sheila", "barney", "flarp", "zxc", "spqr", ";wombat", "shme", _
"foo", "bar", "baz", "bongo", "spam", "eggs", "snork", "foo", _
"bar", "zot", "blarg", "wibble", "toto", "titi", "tata", _
"tutu", "pippo", "pluto", "paperino", "aap", "noot", "mies", _
"oogle", "foogle", "boogle", "zork", "gork", "bork"
DIM needle AS STRING, found AS LONG, lastFound AS LONG
DO
needle = INPUTBOX$("Word to search for? (Leave blank to exit)")
IF needle <> "" THEN
' collate ucase -> case insensitive
ARRAY SCAN haystack(), COLLATE UCASE, = needle, TO found
IF found > 0 THEN
lastFound = found
MSGBOX "Found """ & needle & """ at index " & TRIM$(STR$(found - 1))
IF found < UBOUND(haystack) THEN
DO
ARRAY SCAN haystack(lastFound), COLLATE UCASE, = needle, TO found
IF found > 0 THEN
MSGBOX "Another occurence of """ & needle & """ at index " & _
TRIM$(STR$(found + lastFound - 1))
lastFound = found + lastFound
ELSE
MSGBOX "No more occurences of """ & needle & """ found"
EXIT DO 'will exit inner DO, not outer
END IF
LOOP
END IF
ELSE
MSGBOX "No occurences of """ & needle & """ found"
END IF
ELSE
EXIT DO
END IF
LOOP
END FUNCTION</lang>
PowerShell
<lang PowerShell> function index($haystack,$needle) {
$index = $haystack.IndexOf($needle)
if($index -eq -1) {
Write-Warning "$needle is absent"
} else {
$index
}
} $haystack = @("word", "phrase", "preface", "title", "house", "line", "chapter", "page", "book", "house") index $haystack "house" index $haystack "paragraph" </lang> Output:
4 WARNING: paragraph is absent
PowerShell Extra credit
The -Verbose switch is available to any advanced function. <lang PowerShell> function Find-Needle {
[CmdletBinding()]
[OutputType([int])]
Param
(
[Parameter(Mandatory=$true, Position=0)]
[string]
$Needle,
[Parameter(Mandatory=$true, Position=1)]
[string[]]
$Haystack,
[switch]
$LastIndex
)
if ($LastIndex)
{
$index = [Array]::LastIndexOf($Haystack,$Needle)
if ($index -eq -1)
{
Write-Verbose "Needle not found in Haystack"
return $index
}
if ((($Haystack | Group-Object | Where-Object Count -GT 1).Group).IndexOf($Needle) -ne -1)
{
Write-Verbose "Last needle found in Haystack at index $index"
}
else
{
Write-Verbose "Needle found in Haystack at index $index (No duplicates were found)"
}
return $index
}
else
{
$index = [Array]::IndexOf($Haystack,$Needle)
if ($index -eq -1)
{
Write-Verbose "Needle not found in Haystack"
}
else
{
Write-Verbose "Needle found in Haystack at index $index"
}
return $index }
}
$haystack = @("word", "phrase", "preface", "title", "house", "line", "chapter", "page", "book", "house") </lang> <lang PowerShell> Find-Needle "house" $haystack </lang>
- Output:
4
<lang PowerShell> Find-Needle "house" $haystack -Verbose </lang>
- Output:
VERBOSE: Needle found in Haystack at index 4 4
<lang PowerShell> Find-Needle "house" $haystack -LastIndex -Verbose </lang>
- Output:
VERBOSE: Last needle found in Haystack at index 9 9
<lang PowerShell> Find-Needle "title" $haystack -LastIndex -Verbose </lang>
- Output:
VERBOSE: Needle found in Haystack at index 3 (No duplicates were found) 3
<lang PowerShell> Find-Needle "something" $haystack -Verbose </lang>
- Output:
VERBOSE: Needle not found in Haystack -1
Prolog
Works with SWI-Prolog <lang Prolog>search_a_list(N1, N2) :- L = ["Zig", "Zag", "Wally", "Ronald", "Bush", "Krusty", "Charlie", "Bush", "Boz", "Zag"],
write('List is :'), maplist(my_write, L), nl, nl,
( nth1(Ind1, L, N1) -> format('~s is in position ~w~n', [N1, Ind1]) ; format('~s is not present~n', [N1])), ( nth1(Ind2, L, N2) -> format('~s is in position ~w~n', [N2, Ind2]) ; format('~s is not present~n', [N2])), ( reverse_nth1(Ind3, L, N1) -> format('~s last position is ~w~n', [N1, Ind3]) ; format('~s is not present~n', [N1])).
reverse_nth1(Ind, L, N) :- reverse(L, RL), length(L, Len), nth1(Ind1, RL, N), Ind is Len - Ind1 + 1.
my_write(Name) :- writef(' %s', [Name]). </lang>
- Output:
?- search_a_list("Zag", "Simpson").
List is : Zig Zag Wally Ronald Bush Krusty Charlie Bush Boz Zag
Zag is in position 2
Simpson is not present
Zag last position is 10
true.
PureBasic
<lang PureBasic>If OpenConsole() ; Open a simple console to interact with user
NewList Straws.s()
Define Straw$, target$="TBA"
Define found
Restore haystack ; Read in all the straws of the haystack.
Repeat
Read.s Straw$
If Straw$<>""
AddElement(Straws())
Straws()=UCase(Straw$)
Continue
Else
Break
EndIf
ForEver
While target$<>""
Print(#CRLF$+"Enter word to search for (leave blank to quit) :"): target$=Input()
ResetList(Straws()): found=#False
While NextElement(Straws())
If UCase(target$)=Straws()
found=#True
PrintN(target$+" found as index #"+Str(ListIndex(Straws())))
EndIf
Wend
If Not found
PrintN("Not found.")
EndIf
Wend
EndIf
DataSection
haystack: Data.s "Zig","Zag","Zig","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo",""
EndDataSection</lang>
Python
<lang python>haystack=["Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo"]
for needle in ("Washington","Bush"):
try: print haystack.index(needle), needle except ValueError, value_error: print needle,"is not in haystack"</lang>
- Output:
Washington is not in haystack 4 Bush
Note that in Python, the index method of a list already raises an exception. The following shows the default information given when the exception is not captured in the program: <lang python>>>> haystack=["Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo"] >>> haystack.index('Bush') 4 >>> haystack.index('Washington') Traceback (most recent call last):
File "<pyshell#95>", line 1, in <module>
haystack.index('Washington')
ValueError: list.index(x): x not in list >>></lang>
There is no built-in method for returning the highest index of a repeated string in a Python list, tuple or array, (although strings have rindex). Instead we need to look for the index in the reversed list and adjust the result. <lang python>>>> def hi_index(needle, haystack): return len(haystack)-1 - haystack[::-1].index(needle)
>>> # Lets do some checks >>> for n in haystack: hi = hi_index(n, haystack) assert haystack[hi] == n, "Hi index is of needle" assert n not in haystack[hi+1:], "No higher index exists" if haystack.count(n) == 1: assert hi == haystack.index(n), "index == hi_index if needle occurs only once"
>>></lang>
R
<lang R>find.needle <- function(haystack, needle="needle", return.last.index.too=FALSE) {
indices <- which(haystack %in% needle)
if(length(indices)==0) stop("no needles in the haystack")
if(return.last.index.too) range(indices) else min(indices)
}</lang> Example usage: <lang R>haystack1 <- c("where", "is", "the", "needle", "I", "wonder") haystack2 <- c("no", "sewing", "equipment", "in", "here") haystack3 <- c("oodles", "of", "needles", "needles", "needles", "in", "here")
find.needle(haystack1) # 4 find.needle(haystack2) # error find.needle(haystack3) # 3 find.needle(haystack3, needle="needles", ret=TRUE) # 3 5</lang>
Racket
The function index returns the index of the the element x in the sequence xs. If the element is not found, then #f is returned. <lang racket>(define (index xs y)
(for/first ([(x i) (in-indexed xs)]
#:when (equal? x y))
i))</lang>
If the last index of an element is needed, for/last is used: <lang racket>(define (index-last xs y)
(for/last ([(x i) (in-indexed xs)]
#:when (equal? x y))
i))</lang>
Both index and index-last can handle any sequence such as lists, vectors, sets etc. Let us test with a linked list: <lang racket>(define haystack '("Zig" "Zag" "Wally" "Ronald" "Bush" "Krusty" "Charlie" "Bush" "Bozo"))
(for/list ([needle '("Bender" "Bush")])
(index haystack needle))
(for/list ([needle '("Bender" "Bush")])
(index-last haystack needle))</lang>
- Output:
'(#f 4) '(#f 7)
REBOL
<lang REBOL>REBOL [ Title: "List Indexing" Author: oofoe Date: 2009-12-06 URL: http://rosettacode.org/wiki/Index_in_a_list ]
locate: func [ "Find the index of a string (needle) in string collection (haystack)." haystack [series!] "List of values to search." needle [string!] "String to find in value list." /largest "Return the largest index if more than one needle." /local i ][ i: either largest [ find/reverse tail haystack needle][find haystack needle] either i [return index? i][ throw reform [needle "is not in haystack."] ] ]
- Note that REBOL uses 1-base lists instead of 0-based like most
- computer languages. Therefore, the index provided will be one
- higher than other results on this page.
haystack: parse "Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo" none
print "Search for first occurance:" foreach needle ["Washington" "Bush"] [ print catch [ reform [needle "=>" locate haystack needle] ] ]
print [crlf "Search for last occurance:"] foreach needle ["Washington" "Bush"] [ print catch [ reform [needle "=>" locate/largest haystack needle] ] ]</lang>
- Output:
Search for first occurance: Washington is not in haystack. Bush => 5 Search for last occurance: Washington is not in haystack. Bush => 8
REXX
version 1
This REXX program searches a collection of string (haystack)
that are stored in a sequential REXX array.
No counter is kept of the number of items,
but they should be numbered consecutively and can't have any gaps.
The haystack items may have any character, including blanks.
A null value isn't allowed in this method of representing values.
<lang rexx>/*REXX program searches a collection of strings (an array of periodic table elements).*/
hay.= /*initialize the haystack collection. */
hay.1 = 'sodium'
hay.2 = 'phosphorous'
hay.3 = 'californium'
hay.4 = 'copernicium'
hay.5 = 'gold'
hay.6 = 'thallium'
hay.7 = 'carbon'
hay.8 = 'silver'
hay.9 = 'curium'
hay.10 = 'copper'
hay.11 = 'helium'
hay.12 = 'sulfur'
needle = 'gold' /*we'll be looking for the gold. */ upper needle /*in case some people capitalize stuff.*/ found=0 /*assume the needle isn't found yet. */
do j=1 while hay.j\== /*keep looking in the haystack. */
_=hay.j; upper _ /*make it uppercase to be safe. */
if _=needle then do; found=1 /*we've found the needle in haystack. */
leave /* ··· and stop looking, of course. */
end
end /*j*/
if found then return j /*return the haystack index number. */
else say needle "wasn't found in the haystack!"
return 0 /*indicates the needle wasn't found. */</lang>
version 2
This REXX program searches a collection of string (haystack)
that are stored in a REXX array (which may have gaps).
A safe counter is kept of the maximum (highest) index in the array,
this counter may be any sufficiently high number.
The array may be out of order (but not recommended!).
<lang rexx>/*REXX program searches a collection of strings (an array of periodic table elements).*/
hay.0 = 1000 /*safely indicate highest item number. */
hay.200 = 'Binilnilium'
hay.98 = 'californium'
hay.6 = 'carbon'
hay.112 = 'copernicium'
hay.29 = 'copper'
hay.114 = 'flerovium'
hay.79 = 'gold'
hay.2 = 'helium'
hay.1 = 'hydrogen'
hay.82 = 'lead'
hay.116 = 'livermorium'
hay.15 = 'phosphorous'
hay.47 = 'silver'
hay.11 = 'sodium'
hay.16 = 'sulfur'
hay.81 = 'thallium'
hay.92 = 'uranium'
/* [↑] sorted by the element name. */
needle = 'gold' /*we'll be looking for the gold. */ upper needle /*in case some people capitalize. */ found=0 /*assume the needle isn't found (yet).*/
do j=1 for hay.0 /*start looking in haystack, item 1. */
_=hay.j; upper _ /*make it uppercase just to be safe. */
if _=needle then do; found=1 /*we've found the needle in haystack. */
leave /* ··· and stop looking, of course. */
end
end /*j*/
if found then return j /*return the haystack index number. */
else say needle "wasn't found in the haystack!"
return 0 /*indicates the needle wasn't found. */</lang>
version 3
This REXX program searches a collection of string (haystack)
that are stored in a REXX array.
This form uses a type of array called a sparse array (with non-numeric indexes).
One drawback of this approach is that the items can't have leading/trailing/imbedded blanks,
nor can they have special characters.
Only letters, numerals, and a few special characters are allowed: !, @, #, $, ?, and _.
This method (finding a needle in a haystack) is extremely fast as there isn't any
table look-up, the "finding" is done by REXX's own internal method of variable lookup,
and, for the most part, it based on a table hashing algorithm.
This method pre-prends an underscore (underbar) to avoid collision with any REXX
variable names. Therefore, there shouldn't be any REXX variable names (in this
program) that have a leading underscore (_).
<lang rexx>/*REXX program searches a collection of strings (an array of periodic table elements).*/
hay.=0 /*initialize the haystack collection. */
hay._sodium = 1
hay._phosphorous = 1
hay._californium = 1
hay._copernicium = 1
hay._gold = 1
hay._thallium = 1
hay._carbon = 1
hay._silver = 1
hay._copper = 1
hay._helium = 1
hay._sulfur = 1
/*underscores (_) are used to NOT ... */
/* ... conflict with variable names. */
needle = 'gold' /*we'll be looking for the gold. */
Xneedle = '_'needle /*prefix an underscore (_) character. */ upper Xneedle /*uppercase: how REXX stores them. */
/*alternative version of above: */
/* Xneedle=translate('_'needle) */
found=hay.Xneedle /*this is it, it's found (or maybe not)*/
if found then return j /*return the haystack index number. */
else say needle "wasn't found in the haystack!"
return 0 /*indicates the needle wasn't found. */</lang>
version 4
This method uses a simple string (so haystack items can't have imbedded blanks in them as well as tabs).
Code was added to uppercase both the haystack and the needle to make the search case insensitive.
Note that the haystack lines are around 200 bytes (I was hoping for intelligent scrolling for <lang>).
<lang rexx>/*REXX program searches a collection of strings (an array of periodic table elements).*/
haystack=, /*names of the first 200 elements of the periodic table*/
'hydrogen helium lithium beryllium boron carbon nitrogen oxygen fluorine neon sodium magnesium aluminum silicon phosphorous sulfur chlorine argon potassium calcium scandium titanium',
'vanadium chromium manganese iron cobalt nickel copper zinc gallium germanium arsenic selenium bromine krypton rubidium strontium yttrium zirconium niobium molybdenum technetium ruthenium',
'rhodium palladium silver cadmium indium tin antimony tellurium iodine xenon cesium barium lanthanum cerium praseodymium neodymium promethium samarium europium gadolinium terbium dysprosium',
'holmium erbium thulium ytterbium lutetium hafnium tantalum tungsten rhenium osmium iridium platinum gold mercury thallium lead bismuth polonium astatine radon francium radium actinium',
'thorium protactinium uranium neptunium plutonium americium curium berkelium californium einsteinium fermium mendelevium nobelium lawrencium rutherfordium dubnium seaborgium bohrium hassium',
'meitnerium darmstadtium roentgenium copernicium Ununtrium flerovium Ununpentium livermorium Ununseptium Ununoctium Ununennium Unbinilium Unbiunium Unbibium Unbitrium Unbiquadium',
'Unbipentium Unbihexium Unbiseptium Unbioctium Unbiennium Untrinilium Untriunium Untribium Untritrium Untriquadium Untripentium Untrihexium Untriseptium Untrioctium Untriennium Unquadnilium',
'Unquadunium Unquadbium Unquadtrium Unquadquadium Unquadpentium Unquadhexium Unquadseptium Unquadoctium Unquadennium Unpentnilium Unpentunium Unpentbium Unpenttrium Unpentquadium',
'Unpentpentium Unpenthexium Unpentseptium Unpentoctium Unpentennium Unhexnilium Unhexunium Unhexbium Unhextrium Unhexquadium Unhexpentium Unhexhexium Unhexseptium Unhexoctium Unhexennium',
'Unseptnilium Unseptunium Unseptbium Unsepttrium Unseptquadium Unseptpentium Unsepthexium Unseptseptium Unseptoctium Unseptennium Unoctnilium Unoctunium Niobium Unocttrium Unoctquadium',
'Unoctpentium Unocthexium Unoctseptium Unoctoctium Unoctennium Unennilium Unennunium Unennbium Unenntrium Unennquadium Unennpentium Unennhexium Unennseptium Unennoctium Unennennium Binilnilium'
needle = 'gold' /*we'll be looking for the gold. */ upper needle haystack /*in case some people capitalize stuff. */ idx=wordpos(needle,haystack) /*use REXX's BIF: WORDPOS */ if idx\==0 then return idx /*return the haystack index number. */
else say needle "wasn't found in the haystack!"
return 0 /*indicates the needle wasn't found. */</lang>
Ring
<lang ring> haystack = ["alpha","bravo","charlie","delta","echo","foxtrot","golf", "hotel","india","juliet","kilo","lima","mike","needle", "november","oscar","papa","quebec","romeo","sierra","tango", "needle","uniform","victor","whisky","x-ray","yankee","zulu"]
needle = "needle" maxindex = len(haystack)
for index = 1 to maxindex
if needle = haystack[index] exit ok
next if index <= maxindex
see "first found at index " + index + nl ok
for last = maxindex to 0 step -1
if needle = haystack[last] exit ok
next if !=index see " last found at index " + last + nl else see "not found" + nl ok </lang> Output:
first found at index : 14 last found at index : 22
Ruby
<lang ruby>haystack = %w(Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo)
%w(Bush Washington).each do |needle|
if (i = haystack.index(needle))
puts "#{i} #{needle}"
else
raise "#{needle} is not in haystack\n"
end
end</lang>
- Output:
4 Bush search_a_list.rb:8:in `block in <main>': Washington is not in haystack (RuntimeError) from search_a_list.rb:4:in `each' from search_a_list.rb:4:in `<main>'
Extra credit <lang ruby>haystack.each do |item|
last = haystack.rindex(item)
if last > haystack.index(item)
puts "#{item} last appears at index #{last}"
break
end
end
- => Bush last appears at index 7</lang>
or <lang ruby>multi_item = haystack.each_index.group_by{|idx| haystack[idx]}.select{|key, val| val.length > 1}
- multi_item is => {"Bush"=>[4, 7]}
multi_item.each do |key, val|
puts "#{key} appears at index #{val}"
end
- => Bush appears at index [4, 7]</lang>
Run BASIC
<lang runbasic>haystack$ = ("Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo Bush ") needle$ = "Zag Wally Bush Chicken"
while word$(needle$,i+1," ") <> ""
i = i + 1 thisNeedle$ = word$(needle$,i," ") + " " j = instr(haystack$,thisNeedle$) k1 = 0 k = instr(haystack$,thisNeedle$,j+1) while k <> 0 k1 = k k = instr(haystack$,thisNeedle$,k+1) wend if j <> 0 then print thisNeedle$;" located at:";j; if k1 <> 0 then print " Last position located at:";k1; print else print thisNeedle$;" is not in the list" end if
wend</lang>
- Output:
Zag located at:5 Wally located at:9 Bush located at:22 Last position located at:52 Chicken is not in the list
Rust
Rust encourages to encode possible errors in function's return type. For example, position returns Option<usize>, which can be None or Some(x).
<lang rust>fn main() {
let haystack=vec!["Zig", "Zag", "Wally", "Ronald", "Bush", "Krusty", "Charlie",
"Bush", "Boz", "Zag"];
println!("First occurence of 'Bush' at {:?}",haystack.iter().position(|s| *s=="Bush"));
println!("Last occurence of 'Bush' at {:?}",haystack.iter().rposition(|s| *s=="Bush"));
println!("First occurence of 'Rob' at {:?}",haystack.iter().position(|s| *s=="Rob"));
} </lang>
- Output:
First occurence of 'Bush' at Some(4) Last occurence of 'Bush' at Some(7) First occurence of 'Rob' at None
Version that panics
<lang rust>fn main() {
let haystack=vec!["Zig", "Zag", "Wally", "Ronald", "Bush", "Krusty", "Charlie",
"Bush", "Boz", "Zag"];
println!("First occurence of 'Bush' at {:?}",haystack.iter().position(|s| *s=="Bush").unwrap());
println!("Last occurence of 'Bush' at {:?}",haystack.iter().rposition(|s| *s=="Bush").unwrap());
println!("First occurence of 'Rob' at {:?}",haystack.iter().position(|s| *s=="Rob").unwrap());
} </lang>
- Output:
First occurence of 'Bush' at 4 Last occurence of 'Bush' at 7 thread '<main>' panicked at 'called `Option::unwrap()` on a `None` value', /home/rustbuild/src/rust-buildbot/slave/stable-dist-rustc-linux/build/src/libcore/option.rs:362 playpen: application terminated with error code 101
Sather
<lang sather>class MAIN is
main is
haystack :ARRAY{STR} := |"Zig", "Zag", "Wally", "Ronald", "Bush", "Krusty", "Charlie", "Bush", "Bozo"|;
needles :ARRAY{STR} := | "Washington", "Bush" |;
loop needle ::= needles.elt!;
index ::= haystack.index_of(needle); if index < 0 then #OUT + needle + " is not in the haystack\n"; else #OUT + index + " " + needle + "\n"; end;
end; end;
end;</lang>
Scala
The method indexOf, defined for all classes inheriting from, or having an implicit conversion to, Seq returns the index of the first element, or -1 if none exists. The method lastIndexOf does the same for the last element. Neither throws an exception, but that's easily done afterwards.
However, a simple implementation, not using those or similar methods might be written like this:
<lang scala>def findNeedles(needle: String, haystack: Seq[String]) = haystack.zipWithIndex.filter(_._1 == needle).map(_._2) def firstNeedle(needle: String, haystack: Seq[String]) = findNeedles(needle, haystack).head def lastNeedle(needle: String, haystack: Seq[String]) = findNeedles(needle, haystack).last</lang>
It does raise an exception if there's no needle.
Scheme
<lang scheme>(define haystack
'("Zig" "Zag" "Wally" "Ronald" "Bush" "Krusty" "Charlie" "Bush" "Bozo"))
(define index-of
(lambda (needle hackstack)
(let ((tail (member needle haystack)))
(if tail
(- (length haystack) (length tail))
(throw 'needle-missing)))))
(define last-index-of
(lambda (needle hackstack)
(let ((tail (member needle (reverse haystack))))
(if tail
(- (length tail) 1)
(throw 'needle-missing)))))</lang>
- Output:
(index-of "Bush" haystack) 4 (last-index-of "Bush" haystack) 7
Sidef
<lang ruby>var haystack = %w(Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo);
%w(Bush Washington).each { |needle|
var i = haystack.first_index{|item| item == needle};
if (i >= 0) {
say "#{i} #{needle}";
} else {
die "#{needle} is not in haystack";
}
}</lang>
- Output:
4 Bush Washington is not in haystack at find.sf line 9.
Extra credit: <lang ruby>var haystack = %w(Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo); say haystack.last_index{|item| item == "Bush"};</lang>
- Output:
7
Slate
<lang slate>define: #haystack -> ('Zig,Zag,Wally,Ronald,Bush,Krusty,Charlie,Bush,Bozo' splitWith: $,). {'Washington'. 'Bush'} do: [| :needle |
(haystack indexOf: needle)
ifNil: [inform: word ; ' is not in the haystack']
ifNotNilDo: [| :firstIndex lastIndex |
inform: word ; ' is in the haystack at index ' ; firstIndex printString.
lastIndex: (haystack lastIndexOf: word).
lastIndex isNotNil /\ (lastIndex > firstIndex) ifTrue:
[inform: 'last occurrence of ' ; word ; ' is at index ' ; lastIndex]]].</lang>
Smalltalk
Smalltalk indexes start at 1. <lang smalltalk>| haystack | haystack :=
'Zig,Zag,Wally,Ronald,Bush,Krusty,Charlie,Bush,Bozo' subStrings: $,.
{ 'Washington' . 'Bush' } do: [:i|
|t l|
t := (haystack indexOf: i).
(t = 0) ifTrue: [ ('%1 is not in the haystack' % { i }) displayNl ]
ifFalse: [ ('%1 is at index %2' % { i . t }) displayNl.
l := ( (haystack size) - (haystack reverse indexOf: i) + 1 ).
( t = l ) ifFalse: [
('last occurence of %1 is at index %2' %
{ i . l }) displayNl ]
]
].</lang>
Standard ML
<lang sml>fun find_index (pred, lst) = let
fun loop (n, []) = NONE
| loop (n, x::xs) = if pred x then SOME n
else loop (n+1, xs)
in
loop (0, lst)
end;
val haystack = ["Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo"];
app (fn needle =>
case find_index (fn x => x = needle, haystack) of
SOME i => print (Int.toString i ^ " " ^ needle ^ "\n")
| NONE => print (needle ^ " is not in haystack\n"))
["Washington", "Bush"];</lang>
Swift
<lang swift>let haystack = ["Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo"] for needle in ["Washington","Bush"] {
if let index = haystack.indexOf(needle) {
print("\(index) \(needle)")
} else {
print("\(needle) is not in haystack")
}
}</lang>
<lang swift>let haystack = ["Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo"] for needle in ["Washington","Bush"] {
if let index = find(haystack, needle) {
println("\(index) \(needle)")
} else {
println("\(needle) is not in haystack")
}
}</lang>
The second task:
<lang swift> // the second part can be done several ways, but extending any Array of Comparable objects is the most generic approach extension Array where Element : Comparable {
func lastIndexMatching(needle:Element) -> Int? {
for i in stride(from: count-1, through: 0, by: -1) {
if self[i] == needle {
return i
}
}
return nil
}
}
for needle in ["Washington","Bush"] {
if let index = haystack.lastIndexMatching(needle) {
print("\(index) \(needle)")
} else {
print("\(needle) is not in haystack")
}
}
</lang>
Tcl
<lang tcl>set haystack {Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo} foreach needle {Bush Washington} {
if {[set idx [lsearch -exact $haystack $needle]] == -1} {
error "$needle does not appear in the haystack"
} else {
puts "$needle appears at index $idx in the haystack"
}
}</lang> Extra credit: <lang tcl>set haystack {Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo} foreach needle {Bush Washington} {
set indices [lsearch -all -exact $haystack $needle]
if {[llength $indices] == 0} {
error "$needle does not appear in the haystack"
} else {
puts "$needle appears first at index [lindex $indices 0] and last at [lindex $indices end]"
}
}</lang>
TorqueScript
--Elm 03:38, 18 June 2012 (UTC)
Find multiple needles in a haystack:
<lang TorqueScript>function findIn(%haystack,%needles) { %hc = getWordCount(%haystack); %nc = getWordCount(%needles);
for(%i=0;%i<%nc;%i++) { %nword = getWord(%needles,%i); %index[%nword] = -1; }
for(%i=0;%i<%hc;%i++) { %hword = getWord(%haystack,%i);
for(%j=0;%j<%nc;%j++) { %nword = getWord(%needles,%j);
if(%hword $= %nword) { %index[%nword] = %i; } } }
for(%i=0;%i<%nc;%i++) { %nword = getWord(%needles,%i); %string = %string SPC %nword@"_"@%index[%nword]; %string = trim(%string); }
return %string; }</lang>
How to use it:
<lang TorqueScript>echo(findIn("Hello world, you are quite sunny today.","quite hello somethingelse"));</lang>
returns:
<lang TorqueScript>=> "quite_4 hello_0 somethingelse_-1"</lang>
TUSCRIPT
<lang tuscript>$$ MODE TUSCRIPT SET haystack="Zig'Zag'Wally'Ronald'Bush'Krusty'Charlie'Bush'Bozo" PRINT "haystack=",haystack LOOP needle="Washington'Bush'Wally" SET table =QUOTES (needle) BUILD S_TABLE needle = table
IF (haystack.ct.needle) THEN BUILD R_TABLE needle = table SET position=FILTER_INDEX(haystack,needle,-) RELEASE R_TABLE needle PRINT "haystack contains ", needle, " on position(s): ",position ELSE PRINT "haystack not contains ",needle ENDIF
RELEASE S_TABLE needle ENDLOOP</lang>
- Output:
haystack=Zig'Zag'Wally'Ronald'Bush'Krusty'Charlie'Bush'Bozo haystack not contains Washington haystack contains Bush on position(s): 5'8 haystack contains Wally on position(s): 3
UNIX Shell
<lang sh>if [ $1 ];then haystack="Zip Zag Wally Ronald Bush Krusty Charlie Bush Bozo"
index=$(echo $haystack|tr " " "\n"|grep -in "^$1$") if [ $? = 0 ];then quantity_of_hits=$(echo $index|tr " " "\n"|wc -l|tr -d " ") first_index=$(echo $index|cut -f 1 -d ":") if [ $quantity_of_hits = 1 ];then echo The sole index for $1 is: $first_index else echo The smallest index for $1 is: $first_index greatest_index=$(echo $index|tr " " "\n"|tail -1|cut -f 1 -d ":") echo "The greatest index for $1 is: $greatest_index";fi else echo $1 is absent from haystatck.;fi else echo Must provide string to find in haystack.;fi</lang>
- Output:
./needle_haystack clay ---> clay is absent from haystatck.
./needle_haystack charlie ---> The sole index for charlie is: 7
./needle_haystack bush ---> The smallest index for bush is: 5
The greatest index for bush is: 8
Ursala
The indices function takes a pair of any type, treats haystack as a list, and returns the pair of indices giving the first and last positions of needle in it, which are numbered from zero and may be equal.
If it's not present, an exception is thrown with a diagnostic message of 'missing'.
The search is expressed by ~|, the built-in distributing filter operator.
<lang Ursala>#import std
indices = ||<'missing'>!% ~&nSihzXB+ ~&lrmPE~|^|/~& num</lang> The explanation is somewhat longer than the program.
- The
^|operator takes a right operand consisting of a pair of functions , and returns a function that takes a pair to the result . - An expression of the form
h/f gwherehis a function taking a pair, is equivalent toh(f,g). - The
~&operator represents the identity function. - The expression
^|/~& numapplied to an argument therefore evaluates tonum - The
numfunction takes any list and transforms it to a list of pairs . - The left operand to the
^|operator, if any, is composed with the function constructed from the right. In this case, the left operand is~&lrmPE~| - The
~|operator takes a predicate as its left operand and returns a function that operates on a pair , where is expected to be a list. The resulting function is evaluated by pairing with each item of , applying the predicate to each pair, and making a list of the items of for which the predicate holds on the pair. - The predicate in this case is
~&lrmPE, which will be passed an input of the form for the -th item in terms of the notation above. - The expression
~&lrmPEhas a root operatorE, which tests for equality, a left operandl, which extracts the left side of its argument, and a right operand ofrmP, which is the reverse composition (P) of the right side extraction (r) operator, followed by a further right side extraction expressed more idiomatically asmwhen the argument in question represents some type of key-value pair. - The predicate therefore compares the left side of , which is , to the right of the right, which is
- The result from
~&lrmPE~|will be a list of pairs of the form , for indices at which appears in the list. - This result is passed to the function
~&nSihzXB, which consists of subexpressionsnSandihzXBthat operate sequentially. - The
nSsubexpression makes a list of the left sides of all items of a list of key-value pairs, in this case constructing a list of indices from the input, and passing it to the subexpressionihzXB. - The subexpression
ihzXBhas a left subexpressioni, a right subexpressionhzXand a rootB. - The
B(mnemonic for "both") operator causes the left subexpression to be applied to the argument as a test, and if the result is non-empty, returns the result of applying the right. - The left subexpression
irepresents the identity function, and tests whether the argument list is non-empty. - If the list is non-empty, the expression
hzXconstructs the pair (X) of the head (h) and the last item (z) of the list given in the argument. - The disjunction operator
||used in an expression of the form||u vwith functionsuandvconstructs a function that appliesvto the argument, returns that result if non-empty, but otherwise returns the the result of applyingvto the argument. - The expression
<'missing'>is a list of strings representing the diagnostic message to be returned in the event of an empty list (corresponding to the not being present). - The constant operator (
!) is used because the message is not data-dependent. - The exception throwing operator (
%) compels the result of its operand to be returned in a way that bypasses the usual flow of control.
Test program: <lang Ursala>#cast %nW
test = indices/'bar' <'foo','bar','baz','bar'></lang>
- Output:
(1,3)
VBScript
Shamelessly derived from the BASIC version. <lang vb> data = "foo,bar,baz,quux,quuux,quuuux,bazola,ztesch,foo,bar,thud,grunt," &_ "foo,bar,bletch,foo,bar,fum,fred,jim,sheila,barney,flarp,zxc," &_ "spqr,wombat,shme,foo,bar,baz,bongo,spam,eggs,snork,foo,bar," &_ "zot,blarg,wibble,toto,titi,tata,tutu,pippo,pluto,paperino,aap," &_ "noot,mies,oogle,foogle,boogle,zork,gork,bork"
haystack = Split(data,",")
Do WScript.StdOut.Write "Word to search for? (Leave blank to exit) " needle = WScript.StdIn.ReadLine If needle <> "" Then found = 0 For i = 0 To UBound(haystack) If UCase(haystack(i)) = UCase(needle) Then found = 1 WScript.StdOut.Write "Found " & Chr(34) & needle & Chr(34) & " at index " & i WScript.StdOut.WriteLine End If Next If found < 1 Then WScript.StdOut.Write Chr(34) & needle & Chr(34) & " not found." WScript.StdOut.WriteLine End If Else Exit do End If Loop </lang>
- Output:
F:\VBScript>cscript /nologo search_a_list.vbs Word to search for? (Leave blank to exit) foo Found "foo" at index 0 Found "foo" at index 8 Found "foo" at index 12 Found "foo" at index 15 Found "foo" at index 27 Found "foo" at index 34 Word to search for? (Leave blank to exit) bar Found "bar" at index 1 Found "bar" at index 9 Found "bar" at index 13 Found "bar" at index 16 Found "bar" at index 28 Found "bar" at index 35 Word to search for? (Leave blank to exit) fff "fff" not found. Word to search for? (Leave blank to exit) F:\VBScript>
Wart
Wart uses the function pos to search a list for an element.
Here's how it's implemented:
<lang python>def (pos x (seq | (head ... tail)) n)
default n :to 0
if seq
if (head = x)
n
(pos x tail n+1)</lang>
- Usage
- :
pos 3 '(1 2 3 4 5) => 2 pos 24 '(1 2 3 4 5) => nil
XPL0
<lang XPL0>\Based on C example: include c:\cxpl\stdlib; \provides StrCmp routine, etc. int Haystack; \('int' is used instead of 'char' for 2D array)
func Search(Str, First); \Return first (or last) index for string in haystack char Str; int First; int I, SI; [I:= 0; SI:= 0; repeat if StrCmp(Str, Haystack(I)) = 0 then
[if First then return I;
SI:= I; \save index
];
I:= I+1;
until Haystack(I) = 0; return SI; ];
[Haystack:= ["Zig", "Zag", "Wally", "Ronald", "Bush",
"Krusty", "Charlie", "Bush", "Boz", "Zag", 0];
Text(0, "Bush is at "); IntOut(0, Search("Bush", true)); CrLf(0); if Search("Washington", true) = 0 then
Text(0, "Washington is not in the haystack^M^J");
Text(0, "First index for Zag: "); IntOut(0, Search("Zag", true)); CrLf(0); Text(0, "Last index for Zag: "); IntOut(0, Search("Zag", false)); CrLf(0); ]</lang>
- Output:
Bush is at 4 Washington is not in the haystack First index for Zag: 1 Last index for Zag: 9
Yorick
<lang yorick>haystack = ["Zig", "Zag", "Wally", "Ronald", "Bush", "Krusty", "Charlie", "Bush", "Bozo"]; needles = ["Bush", "Washington"]; for(i = 1; i <= numberof(needles); i++) {
w = where(haystack == needles(i));
if(!numberof(w))
error, "Needle "+needles(i)+" not found";
write, format="Needle %s appears first at index %d\n", needles(i), w(1);
if(numberof(w) > 1)
write, format="Needle %s appears last at index %d\n", needles(i), w(0);
}</lang>
zkl
<lang zkl>L("Krusty","Charlie","Bozo","Bozo").index("Charlie") //--> 1 L("Krusty","Charlie","Bozo","Bozo").index("fred") //--> throws index error</lang> Find last needle: <lang zkl>haystack:=L("Krusty","Charlie","Bozo","Bozo"); haystack.filterNs('==("Bozo"))[-1]; // -->3, indexError if not found haystack.len() - 1 - haystack.reverse().index("Bozo"); // or this</lang> Use a bit bucket of ASCIIZ strings <lang zkl>haystack:=Data(0,String,"Krusty","Charlie","Bozo","Bozo"); if((n:=haystack.findString("Charlie")) != Void) n else throw(Exception.IndexError); //-->7</lang>
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