Search a list

From Rosetta Code
Task
Search a list
You are encouraged to solve this task according to the task description, using any language you may know.
Task[edit]

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.

Extra credit

Return the largest index to a needle that has multiple occurrences in the haystack.

See also

ACL2[edit]

(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))

ActionScript[edit]

Using the built-in Error class[edit]

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;
}

Using a custom error[edit]

In StringNotFoundError.as:

package {
public class StringNotFoundError extends Error {
public function StringNotFoundError(message:String) {
super(message);
}
}
}

In a separate file:

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;
}
 

Ada[edit]

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;
Output:
Washington is not in
Bushat 5

Aime[edit]

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;
}
Output:
Bush is at 4
Washington is not in the haystack
Zag is at 1

ALGOL 68[edit]

Using a FORMAT "value error" exception[edit]

Works with: ALGOL 68 version Revision 1 - no extensions to language used
Works with: ALGOL 68G version Any - tested with release 1.18.0-9h.tiny
 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
)
Output:
Washington is not in haystack
5 Bush

Using a manual FOR loop with no exception[edit]

Works with: ALGOL 68 version Revision 1 - no extensions to language used
Works with: ALGOL 68G version Any - tested with release 1.18.0-9h.tiny
 []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
)
Output:
Washington is not in haystack
5 Bush

AutoHotkey[edit]

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"
}

AWK[edit]

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!)

#! /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";
}
}

BASIC[edit]

Works with: 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
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[edit]

The index of this simple implementation is 1-based. The "haystack" data are borrowed from the BASIC implementation.

@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
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[edit]

      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

Bracmat[edit]

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.

(     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."
)
);
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[edit]

blsq ) {"Zig" "Zag" "Wally" "Bush" "Ronald" "Bush"}"Bush"Fi
3

If you want all indices:

blsq ) {"Zig" "Zag" "Wally" "Bush" "Ronald" "Bush"}{"Bush"==}fI
{3 5}

C[edit]

#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;
}
Output:
Bush is at 4
Washington is not in the haystack
First index for Zag: 1
Last index for Zag: 9

C++[edit]

Works with: g++ version 4.1.2 20061115 (prerelease) (Debian 4.1.1-21)

The following code shows three different ways to solve the task.

#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");
}
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[edit]

/* 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 */
Output:
l contains: Bush at 7 10 11 
Obama not found
l contains: Homer at 3 
Sherlock not found

C#[edit]

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);
}
}
}

Ceylon[edit]

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);
}

Clojure[edit]

(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)))

Extra credit: Since Clojure vectors implement java.util.List, you can switch .indexOf for .lastIndexOf to find the highest index of your value.

COBOL[edit]

*> 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
.
Output:
Found Bush    at +000000005.
Goofy   not found.
Found last of Bush    at +000000008.

Common Lisp[edit]

(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"))))))
Output:
WASHINGTON is not in haystack
4 BUSH

The position function solves this task elegantly.

 
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

D[edit]

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);
}

Delphi[edit]

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.
Output:
3
needle

DWScript[edit]

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

E[edit]

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

Elena[edit]

#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. ].
].
].

Elixir[edit]

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)
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[edit]

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.

-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]).
Output:
Washington is not in haystack.
Bush at position 5.

Euphoria[edit]

Works with: Euphoria version 4.0.3, 4.0.0 RC1 and later

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.

 
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()
 
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#[edit]

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.

Factor[edit]

: 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
( scratchpad ) { "a" "b" "c" "d" "c" } "c" find-index .
2
( scratchpad ) { "a" "b" "c" "d" "c" } "c" find-last-index .
4

Forth[edit]

Works with: 4tH version 3.61.5
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


Works with any ANS Forth

Needs the FMS-SI (single inheritance) library code located here: http://soton.mpeforth.com/flag/fms/index.html

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
 

Fortran[edit]

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

FreeBASIC[edit]

FreeBASIC doesn't have exceptions so we use a different approach to check if the needle is present or not in the haystack:

' FB 1.05.0 Win64
' Works FB 1.05.0 Linux Mint 64
 
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
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

Gambas[edit]

Public Sub Form_Open()
Dim sHaystack As String[] = ["Zig", "Zag", "Wally", "Ronald", "Bush", "Krusty", "Charlie", "Bush", "Boz", "Zag"]
Dim sNeedle As String = "Charlie"
Dim sOutput As String = "No needle found!"
Dim siCount As Short
 
For siCount = 0 To sHaystack.Max
If sNeedle = sHaystack[siCount] Then
sOutPut = sNeedle & " found at index " & Str(siCount)
Break
End If
Next
 
Print sOutput
 
End

Output:

Charlie found at index 6


GAP[edit]

# 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

See also Eratosthenes and Shuffle functions in RosettaCode.

Go[edit]

Data used by both examples below. (You can give multiple files to go run, like $ go run data.go example.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"}

Linear search[edit]

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
}
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[edit]

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.

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])
}
}
Output:
soap [15]
gold [77 81]
fire []

Groovy[edit]

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
}
}
Output:
Washington is not in haystack
First index: 4 Bush
Last index:  7 Bush
First index: 2 Wally
Last index:  2 Wally

Haskell[edit]

Libraries and data:

import Data.List
 
haystack=["Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo"]
needles = ["Washington","Bush"]

I use 'lambda' notation for readability.

Find 'just' an index:
*Main> map (\x -> (x,elemIndex x haystack)) needles
[("Washington",Nothing),("Bush",Just 4)]

Want to know if there are there more Bushes hiding in the haystack?

*Main> map (\x -> (x,elemIndices x haystack)) needles
[("Washington",[]),("Bush",[4,7])]

To be complete. Here is the 'point free' version of the task:

import Control.Monad
import Control.Arrow
 
*Main> map (ap (,) (flip elemIndex haystack)) needles
[("Washington",Nothing),("Bush",Just 4)]

HicEst[edit]

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

Icon and Unicon[edit]

 
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

Taken from the public domain Icon Programming Library's lindex in lists which generates list indices for x of any type

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
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[edit]

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.

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
)
Output:
firstIndex("Washington"): Washington is not in haystack
lastIndex("Washington"): Washington is not in haystack
firstIndex("Bush"): 4
lastIndex("Bush"): 7

J[edit]

J has a general and optimized lookup function, i.

For example:

   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

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:

    Haystack ;:^:_1@(] ,. [ ((<'is not in haystack')"_)`(#@[ I.@:= ])`(8!:0@])} i.) Needles
Washington is not in haystack
Bush 4

Or broken up into components and defined as a verb/function for finding the last positions:

   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

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[edit]

for Lists, they have an indexOf() method:

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);
}

for arrays, you have to do it manually:

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);
}
Output:
Washington is not in haystack
4 Bush

JavaScript[edit]

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"
}
The following
Works with: JavaScript version 1.6
:
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
}
}


Or, generalising enough (in ES5) to allow for varying definitions of the type of match we are looking for:

(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
];
})
}
})();

Output:

{
"first": [
[
"bush",
4
],
[
"washington",
"Error: not found"
]
],
"last": [
[
"bush",
7
],
[
"washington",
"Error: not found"
]
]
}

jq[edit]

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 "# =>":

 
["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

Julia[edit]

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

K[edit]

  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
Output:
(("Washington"
"Not Found")
("Bush"
4))

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).

  Haystack2: Haystack,,"Bush"
Needles2:Needles,,"Zag"
{+(x;{:[#&x;,/?(*&x;*|&x);"Not found"]}'+x _sm/:y)}[Needles2;Haystack2]
Output:
(("Washington"
"Not found")
("Bush"
4 9)
("Zag"
1))

Kotlin[edit]

// 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")
}
 
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[edit]

: 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 .
Output:
[ hello is not in haystack
  [    1     6  ]
]

Lasso[edit]

Lasso arrays have a findindex method which returns all matching indexes. [1]

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.')
^}
Output:
5
8
Washington is not in haystack.

Liberty BASIC[edit]

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

Lingo[edit]

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"

Lisaac[edit]

+ 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;
};
};

[edit]

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


Lua[edit]

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

Mathematica[edit]

This examples shows you the first appearance, the last appearance, and all appearances (as a list):

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]]

gives back:

2
7
{2,7}

MATLAB[edit]

Collections of strings are stored in cell arrays in MATLAB. The solution bellow will only work for a cell array of this construction:
stringCollection = {'string1','string2',...,'stringN'}
It will not work for any other construction, for example:
stringCollection = {{'string1'},{'string2'},{...},{'stringN'}}

searchCollection.m:

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
Output:
>> 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.

MAXScript[edit]

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
)
)
Output:
Washington is not in haystack
5 Bush

Maxima[edit]

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));
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[edit]

/* 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
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[edit]

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")

Objective-C[edit]

Works with: Objective-C version 2.0+
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);
}

Objeck[edit]

use Collection;
 
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();
};
}
}

OCaml[edit]

# 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 = ()

Oforth[edit]

indexOf returns null if an object is not into a collection, not an exception.

: 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
Output:
5
8
[1:interpreter] ExRuntime : Not found <Washington>

ooRexx[edit]

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.

-- 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)

Oz[edit]

No such function exists for the built-in list type (the operation is quite inefficient, after all). A possible implementation:

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

PARI/GP[edit]

Works with: PARI/GP version 2.4.3 and above
find(v,n)={
my(i=setsearch(v,n));
if(i,
while(i>1, if(v[i-1]==n,i--))
,
error("Could not find")
);
i
};

Pascal[edit]

See Delphi

Perl[edit]

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";
}
}
Output:
Washington is not in haystack
4 Bush

You could install a non-standard module List::MoreUtils:

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";
}
}

Alternatively, if you need to do this a lot, you could create a hash table mapping values to indices in the haystack:

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";
}
}
Output:
Washington is not in haystack
7 Bush

Perl 6[edit]

Works with: Rakudo Star version 2016.07
my @haystack = <Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo>;
 
for <Washington Bush> -> $needle {
say "$needle -- { @haystack.first($needle, :k) // 'not in haystack' }";
}
Output:
Washington -- not in haystack
Bush -- 4


Or, including the "extra credit" task:

Works with: Rakudo Star version 2016.07
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";
}
}
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:

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' }";
}

Phix[edit]

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)

PHP[edit]

$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";
}
Output:
Washington is not in haystack
4 Bush

PicoLisp[edit]

Note that in PicoLisp all indexes are one-based (the first element has the position '1')

(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) )
Output:
Washington not found
Bush 5
Bush 8

PL/I[edit]

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;

PowerBASIC[edit]

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

PowerShell[edit]

Works with: PowerShell version 4.0
 
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"
 

Output:

4
WARNING: paragraph is absent

PowerShell Extra credit[edit]

The -Verbose switch is available to any advanced function.

 
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")
 
 
Find-Needle "house" $haystack
 
Output:
4
 
Find-Needle "house" $haystack -Verbose
 
Output:
VERBOSE: Needle found in Haystack at index 4
4
 
Find-Needle "house" $haystack -LastIndex -Verbose
 
Output:
VERBOSE: Last needle found in Haystack at index 9
9
 
Find-Needle "title" $haystack -LastIndex -Verbose
 
Output:
VERBOSE: Needle found in Haystack at index 3  (No duplicates were found)
3
 
Find-Needle "something" $haystack -Verbose
 
Output:
VERBOSE: Needle not found in Haystack
-1

Prolog[edit]

Works with SWI-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]).
 
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[edit]

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

Python[edit]

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"
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:

>>> 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
>>>

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.

>>> 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"
 
>>>

R[edit]

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)
}

Example usage:

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


Racket[edit]

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.

(define (index xs y)
(for/first ([(x i) (in-indexed xs)]
#:when (equal? x y))
i))

If the last index of an element is needed, for/last is used:

(define (index-last xs y)
(for/last ([(x i) (in-indexed xs)]
#:when (equal? x y))
i))

Both index and index-last can handle any sequence such as lists, vectors, sets etc. Let us test with a linked list:

(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))
Output:
'(#f 4)
'(#f 7)

REBOL[edit]

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]
]
]
Output:
Search for first occurance:
Washington is not in haystack.
Bush => 5

Search for last occurance:
Washington is not in haystack.
Bush => 8

REXX[edit]

version 1[edit]

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.

/*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. */

version 2[edit]

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!).

/*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. */

version 3[edit]

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   (_).

/*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. */

version 4[edit]

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>).

/*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. */

Ring[edit]

 
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
 

Output:

first found at index : 14
 last found at index : 22

Ruby[edit]

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
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

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

or

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]

Run BASIC[edit]

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
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[edit]

Rust encourages to encode possible errors in function's return type. For example, position returns Option<usize>, which can be None or Some(x).

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"));
}
 
Output:
First occurence of 'Bush' at Some(4)
Last occurence of 'Bush' at Some(7)
First occurence of 'Rob' at None

Version that panics[edit]

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());
}
 
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[edit]

Translation of: C_sharp
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;

Scala[edit]

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:

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

It does raise an exception if there's no needle.

Scheme[edit]

(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)))))
Output:
(index-of "Bush" haystack)
4
(last-index-of "Bush" haystack)
7

Sidef[edit]

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";
}
}
Output:
4 Bush
Washington is not in haystack at find.sf line 9.

Extra credit:

var haystack = %w(Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo);
say haystack.last_index{|item| item == "Bush"};
Output:
7

Slate[edit]

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]]].

Smalltalk[edit]

Works with: GNU Smalltalk

Smalltalk indexes start at 1.

| 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 ]
]
].

Standard ML[edit]

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"];

Swift[edit]

Works with: Swift version 2.x+
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")
}
}
Works with: Swift version 1.x
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")
}
}

The second task:

Works with: Swift version 2.x+
 
// 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")
}
}
 
 
 

Tcl[edit]

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"
}
}

Extra credit:

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]"
}
}

TorqueScript[edit]

--Elm 03:38, 18 June 2012 (UTC)

Find multiple needles in a haystack:

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;
}

How to use it:

echo(findIn("Hello world, you are quite sunny today.","quite hello somethingelse"));

returns:

=> "quite_4 hello_0 somethingelse_-1"

TUSCRIPT[edit]

$$ 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
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[edit]

Works with: Almquist Shell
Works with: bash
Works with: ksh93
Works with: pdksh
Works with: Z Shell
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
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[edit]

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.

#import std
 
indices = ||<'missing'>!% ~&nSihzXB+ ~&lrmPE~|^|/~& num

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 g where h is a function taking a pair, is equivalent to h(f,g).
  • The ~& operator represents the identity function.
  • The expression ^|/~& num applied to an argument therefore evaluates to num
  • The num function 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 ~&lrmPE has a root operator E, which tests for equality, a left operand l, which extracts the left side of its argument, and a right operand of rmP, which is the reverse composition (P) of the right side extraction (r) operator, followed by a further right side extraction expressed more idiomatically as m when 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 subexpressions nS and ihzXB that operate sequentially.
  • The nS subexpression 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 subexpression ihzXB.
  • The subexpression ihzXB has a left subexpression i, a right subexpression hzX and a root B.
  • 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 i represents the identity function, and tests whether the argument list is non-empty.
  • If the list is non-empty, the expression hzX constructs 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 v with functions u and v constructs a function that applies v to the argument, returns that result if non-empty, but otherwise returns the the result of applying v to 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:

#cast %nW
 
test = indices/'bar' <'foo','bar','baz','bar'>
Output:
(1,3)

VBScript[edit]

Shamelessly derived from the BASIC version.

 
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
 
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[edit]

Wart uses the function pos to search a list for an element. Here's how it's implemented:

def (pos x (seq | (head ... tail)) n)
default n :to 0
if seq
if (head = x)
n
(pos x tail n+1)
Usage
:
pos 3 '(1 2 3 4 5)
=> 2
pos 24 '(1 2 3 4 5)
=> nil

XPL0[edit]

\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);
]
Output:
Bush is at 4
Washington is not in the haystack
First index for Zag: 1
Last index for Zag: 9

Yorick[edit]

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);
}

zkl[edit]

L("Krusty","Charlie","Bozo","Bozo").index("Charlie") //--> 1
L("Krusty","Charlie","Bozo","Bozo").index("fred") //--> throws index error

Find last needle:

haystack:=L("Krusty","Charlie","Bozo","Bozo");
haystack.filterNs('==("Bozo"))[-1]; // -->3, indexError if not found
haystack.len() - 1 - haystack.reverse().index("Bozo"); // or this

Use a bit bucket of ASCIIZ strings

haystack:=Data(0,String,"Krusty","Charlie","Bozo","Bozo");
if((n:=haystack.findString("Charlie")) != Void) n else throw(Exception.IndexError);
//-->7