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# Remove duplicate elements

Remove duplicate elements
You are encouraged to solve this task according to the task description, using any language you may know.
Given an Array, derive a sequence of elements in which all duplicates are removed.

There are basically three approaches seen here:

• Put the elements into a hash table which does not allow duplicates. The complexity is O(n) on average, and O(n2) worst case. This approach requires a hash function for your type (which is compatible with equality), either built-in to your language, or provided by the user.
• Sort the elements and remove consecutive duplicate elements. The complexity of the best sorting algorithms is O(n log n). This approach requires that your type be "comparable", i.e., have an ordering. Putting the elements into a self-balancing binary search tree is a special case of sorting.
• Go through the list, and for each element, check the rest of the list to see if it appears again, and discard it if it does. The complexity is O(n2). The up-shot is that this always works on any type (provided that you can test for equality).

## 360 Assembly

Translation of: PL/I
`*        Remove duplicate elements - 18/10/2015REMDUP   CSECT         USING  REMDUP,R15         set base register         SR     R6,R6              i=0         LA     R8,1               k=1LOOPK    C      R8,N               do k=1 to n         BH     ELOOPK         LR     R1,R8              k         SLA    R1,2         L      R9,T-4(R1)         e=t(k)         LR     R7,R8              k         BCTR   R7,0               j=k-1LOOPJ    C      R7,=F'1'           do j=k-1 to 1 by -1         BL     ELOOPJ         LR     R1,R7              j         SLA    R1,2         L      R2,T-4(R1)         t(j)         CR     R9,R2              if e=t(j) then goto iter         BE     ITER         BCTR   R7,0               j=j-1         B      LOOPJELOOPJ   LA     R6,1(R6)           i=i+1         LR     R1,R6              i         SLA    R1,2         ST     R9,T-4(R1)         t(i)=eITER     LA     R8,1(R8)           k=k+1         B      LOOPKELOOPK   LA     R10,PG             [email protected]         LA     R8,1               k=1LOOP     CR     R8,R6              do k=1 to i         BH     ELOOP         LR     R1,R8              k         SLA    R1,2         L      R2,T-4(R1)         t(k)         XDECO  R2,PG+80           edit t(k)         MVC    0(3,R10),PG+89     output t(k) on 3 char         LA     R10,3(R10)         pgi=pgi+3         LA     R8,1(R8)           k=k+1         B      LOOPELOOP    XPRNT  PG,80              print buffer         XR     R15,R15            set return code         BR     R14                return to callerT        DC     F'6',F'6',F'1',F'5',F'6',F'2',F'1',F'7',F'5',F'22'         DC     F'4',F'19',F'1',F'1',F'6',F'8',F'9',F'10',F'11',F'12'N        DC     A((N-T)/4)         number of T itemsPG       DC     CL92' '         YREGS         END    REMDUP`
Output:
`  6  1  5  2  7 22  4 19  8  9 10 11 12`

## 8080 Assembly

This routine works on arrays of bytes, and keeps track of which bytes it has seen in a 256-byte array.

`		org	100h		jmp	test		;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;		;; Given an array of bytes starting at HL with length BC,		;; remove all duplicates in the array. The new end of the array		;; is returned in HL. A page of memory (256 bytes) is required		;; to mark which bytes have been seen.uniqpage:	equ	3	; Page to use - a compile-time constant.				; This would need to be set to a page that				; the rest of the program doesn't need.uniq:		xra	a	; Zero out the page		lxi	d,uniqpage * 256uniqzero:	stax	d	; Zero out a byte		inr	e	; And do the next byte		jnz	uniqzero		mov	d,h	; Keep a second pointer to the array in DE		mov	e,luniqpos:	ldax	d	; Read from high pointer		mov	m,a	; Write to low pointer		inx	d	; Increment the high pointer		push	h	; Keep low pointer around		mvi	h,uniqpage			mov	l,a	; Have we seen this byte yet?		cmp	m			mov	m,a	; No matter what, we've certainly seen it now		pop	h	; Bring back the low pointer		jz	uniqno	; If we already had it, don't increment low ptr		inx	h	; IF we didn't, do increment ituniqno:		dcx	b	; One fewer byte left		mov	a,b	; If there are zero bytes left,		ora	c		rz		; Then return to caller		jmp	uniqpos	; Otherwise, do the next byte		;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;		;; Testing code: read a string from the CP/M console, run		;; uniq, then print the output.test:		lxi	d,bufdef	; Read a string		mvi	c,10		call	5		lxi	d,nl		; Output on new line		mvi	c,9		call	5		;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;		lda	bufdef+1	; Length of input string		mov	c,a		; Extend to 16-bit (since uniq supports		mvi	b,0		; long arrays)		lxi	h,buf		; Location of input string		call	uniq		; Only the unique bytes		;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;		mvi	m,'\$'		; Mark the (string) end with '\$'		lxi 	d,buf		; Print the string, which now has had		mvi	c,9		; all duplicates removed. 		jmp	5 nl:		db	13,10,'\$'bufdef:		db	127,0buf:`

## ACL2

`(remove-duplicates xs)`

Works with: GNAT version GPL 2018
`with Ada.Containers.Ordered_Sets, Ada.Text_IO;use Ada.Text_IO; procedure Duplicate is		package Int_Sets is new Ada.Containers.Ordered_Sets (Integer);	Nums : constant array (Natural range <>) of Integer := (1,2,3,4,5,5,6,7,1);	Unique : Int_Sets.Set;begin	for n of Nums loop		Unique.Include (n);	end loop;	for e of Unique loop		Put (e'img);	end loop;end Duplicate;`

## Aime

Using an index:

`index x; list(1, 2, 3, 1, 2, 3, 4, 1).ucall(i_add, 1, x, 0);x.i_vcall(o_, 1, " ");o_newline();`
Output:
` 1 2 3 4`

Order preserving solution:

`index x; for (, integer a in list(8, 2, 1, 8, 2, 1, 4, 8)) {    if ((x[a] += 1) == 1) {        o_(" ", a);    }}o_newline();`
Output:
` 8 2 1 4`

## ALGOL 68

Using the associative array code from Associative_array/Iteration#ALGOL_68

`# use the associative array in the Associate array/iteration task    ## this example uses strings - for other types, the associative       ## array modes AAELEMENT and AAKEY should be modified as required     #PR read "aArray.a68" PR # returns the unique elements of list                                #PROC remove duplicates = ( []STRING list )[]STRING:     BEGIN        REF AARRAY elements := INIT LOC AARRAY;        INT        count    := 0;        FOR pos FROM LWB list TO UPB list DO            IF NOT ( elements CONTAINSKEY list[ pos ] ) THEN                # first occurance of this element                    #                elements // list[ pos ] := "";                count +:= 1            FI        OD;        # construct an array of the unique elements from the         #        # associative array - the new list will not necessarily be   #        # in the original order                                      #        [ count ]STRING result;        REF AAELEMENT e := FIRST elements;        FOR pos WHILE e ISNT nil element DO            result[ pos ] := key OF e;            e := NEXT elements        OD;        result     END; # remove duplicates # # test the duplicate removal                                         #print( ( remove duplicates( ( "A", "B", "D", "A", "C", "F", "F", "A" ) ), newline ) ) `

## APL

Works with: Dyalog APL

The primitive monad ∪ means "unique", so:

`∪ 1 2 3 1 2 3 4 11 2 3 4`
Works with: APL2
`w←1 2 3 1 2 3 4 1     ((⍳⍨w)=⍳⍴w)/w1 2 3 4`

## AppleScript

`unique({1, 2, 3, "a", "b", "c", 2, 3, 4, "b", "c", "d"}) on unique(x)    set R to {}    repeat with i in x        if i is not in R then set end of R to i's contents    end repeat    return Rend unique`

Or, more generally, we can allow for customised definitions of equality and duplication, by following the Haskell prelude in defining a nub :: [a] -> [a] function which is a special case of nubBy :: (a -> a -> Bool) -> [a] -> [a]

In the following example, equality is defined as case-insensitive for strings. We would obtain a different list of unique strings by adjusting the Eq :: a -> a -> Bool function to make it consider case.

Translation of: JavaScript
`-- CASE-INSENSITIVE UNIQUE ELEMENTS ------------------------------------------ -- nub :: [a] -> [a]on nub(xs)    -- Eq :: a -> a -> Bool    script Eq        on |λ|(x, y)            ignoring case                x = y            end ignoring        end |λ|    end script     nubBy(Eq, xs)end nub  -- TEST ----------------------------------------------------------------------on run    {intercalate(space, ¬        nub(splitOn(space, "4 3 2 8 0 1 9 5 1 7 6 3 9 9 4 2 1 5 3 2"))), ¬        intercalate("", ¬            nub(characters of "abcabc ABCABC"))}     --> {"4 3 2 8 0 1 9 5 7 6", "abc "}end run  -- GENERIC FUNCTIONS --------------------------------------------------------- -- filter :: (a -> Bool) -> [a] -> [a]on filter(f, xs)    tell mReturn(f)        set lst to {}        set lng to length of xs        repeat with i from 1 to lng            set v to item i of xs            if |λ|(v, i, xs) then set end of lst to v        end repeat        return lst    end tellend filter -- intercalate :: Text -> [Text] -> Texton intercalate(strText, lstText)    set {dlm, my text item delimiters} to {my text item delimiters, strText}    set strJoined to lstText as text    set my text item delimiters to dlm    return strJoinedend intercalate -- Lift 2nd class handler function into 1st class script wrapper -- mReturn :: Handler -> Scripton mReturn(f)    if class of f is script then        f    else        script            property |λ| : f        end script    end ifend mReturn -- nubBy :: (a -> a -> Bool) -> [a] -> [a]on nubBy(fnEq, xxs)     set lng to length of xxs    if lng > 1 then        set x to item 1 of xxs        set xs to items 2 thru -1 of xxs        set p to mReturn(fnEq)         -- notEq :: a -> Bool        script notEq            on |λ|(a)                not (p's |λ|(a, x))            end |λ|        end script         {x} & nubBy(fnEq, filter(notEq, xs))    else        xxs    end ifend nubBy -- splitOn :: Text -> Text -> [Text]on splitOn(strDelim, strMain)    set {dlm, my text item delimiters} to {my text item delimiters, strDelim}    set lstParts to text items of strMain    set my text item delimiters to dlm    return lstPartsend splitOn`
Output:
`{"4 3 2 8 0 1 9 5 7 6", "abc "}`

## Applesoft BASIC

`100 DIM L\$(15)110 L\$(0) = "NOW"120 L\$(1) = "IS"130 L\$(2) = "THE"140 L\$(3) = "TIME"150 L\$(4) = "FOR"160 L\$(5) = "ALL"170 L\$(6) = "GOOD"180 L\$(7) = "MEN"190 L\$(8) = "TO"200 L\$(9) = "COME"210 L\$(10) = "TO"220 L\$(11) = "THE"230 L\$(12) = "AID"240 L\$(13) = "OF"250 L\$(14) = "THE"260 L\$(15) = "PARTY." 300 N = 15310 GOSUB 400320 FOR I = 0 TO N330     PRINT L\$(I) " " ;340 NEXT350 PRINT360 END 400 REMREMOVE DUPLICATES410 FOR I = N TO 1 STEP -1420    I\$ = L\$(I)430    FOR J = 0 TO I - 1440        EQ = I\$ = L\$(J)450        IF NOT EQ THEN NEXT J460    IF EQ THEN GOSUB 500470 NEXT I480 RETURN 500 REMREMOVE ELEMENT510 L\$(I) = L\$(N)520 L\$(N) = ""530 N = N - 1540 RETURN`

## Arturo

`arr: #(1 2 3 2 1 2 3 4 5 3 2 1) print [unique arr]`
Output:
`#(1 2 3 4 5)`

## AutoHotkey

Built in Sort has an option to remove duplicates

`a = 1,2,1,4,5,2,15,1,3,4Sort, a, a, NUD`,MsgBox % a  ; 1,2,3,4,5,15`

## AWK

We produce an array a with duplicates from a string; then index a second array b with the contents of a, so that duplicates make only one entry; then produce a string with the keys of b, which is finally output.

`\$ awk 'BEGIN{split("a b c d c b a",a);for(i in a)b[a[i]]=1;r="";for(i in b)r=r" "i;print r}'a b c d`

## BBC BASIC

`      DIM list\$(15)      list\$() = "Now", "is", "the", "time", "for", "all", "good", "men", \      \         "to", "come", "to", "the", "aid", "of", "the", "party."      num% = FNremoveduplicates(list\$())      FOR i% = 0 TO num%-1        PRINT list\$(i%) " " ;      NEXT      PRINT      END       DEF FNremoveduplicates(l\$())      LOCAL i%, j%, n%, i\$      n% = 1      FOR i% = 1 TO DIM(l\$(), 1)        i\$ = l\$(i%)        FOR j% = 0 TO i%-1          IF i\$ = l\$(j%) EXIT FOR        NEXT        IF j%>=i% l\$(n%) = i\$ : n% += 1      NEXT      = n%`
Output:
```Now is the time for all good men to come aid of party.
```

## Bracmat

Here are three solutions. The first one (A) uses a hash table, the second (B) uses a pattern for spotting the elements that have a copy further on in the list and only adds those elements to the answer that don't have copies further on. The third solution (C) utilises an mechanism that is very typical of Bracmat, namely that sums (and also products) always are transformed to a normalised form upon evaluation. Normalisation means that terms are ordered in a unique way and that terms that are equal, apart from a numerical factor, are replaced by a single term with a numerical factor that is the sum of the numerical factors of each term. The answer is obtained by replacing all numerical factors by `1` as the last step.

The list contains atoms and also a few non-atomic expressions. The hash table needs atomic keys, so we apply the `str` function when searching and inserting elements.

`2 3 5 7 11 13 17 19 cats 222 (-100.2) "+11" (1.1) "+7" (7.) 7 5 5 3 2 0 (4.4) 2:?LIST (A=  ( Hashing  =   h elm list    .   new\$hash:?h      &   whl        ' ( !arg:%?elm ?arg          & ( (h..find)\$str\$!elm            | (h..insert)\$(str\$!elm.!elm)            )          )      & :?list      &   (h..forall)        \$ (          = .!arg:(?.?arg)&!arg !list:?list          )      & !list  )& put\$("Solution A:" Hashing\$!LIST \n,LIN)); (B=  ( backtracking  =   answr elm    .     :?answr        &   !arg          :   ?              (   %?`elm                  ?                  ( !elm ?                  | &!answr !elm:?answr                  )              & ~              )      | !answr  )& put\$("Solution B:" backtracking\$!LIST \n,LIN)); (C=  ( summing  =   sum car LIST    .   !arg:?LIST      & 0:?sum      &   whl        ' ( !LIST:%?car ?LIST          & (.!car)+!sum:?sum          )      &   whl        ' ( !sum:#*(.?el)+?sum          & !el !LIST:?LIST          )      & !LIST  )& put\$("Solution C:" summing\$!LIST \n,LIN)); ( !A& !B& !C&)`

Only solution B produces a list with the same order of elements as in the input.

```Solution A: 19 (4.4) 17 11 13 (1.1) (7.) 222 +11 7 5 3 2 0 cats (-100.2) +7
Solution B: 11 13 17 19 cats 222 (-100.2) +11 (1.1) +7 (7.) 7 5 3 0 (4.4) 2
Solution C: (7.) (4.4) (1.1) (-100.2) cats 222 19 17 13 11 7 5 3 2 0 +7 +11```

## Brat

`some_array = [1 1 2 1 'redundant' [1 2 3] [1 2 3] 'redundant'] unique_array = some_array.unique`

## C

### O(n^2) version, using linked lists

Since there's no way to know ahead of time how large the new data structure will need to be, we'll return a linked list instead of an array.

`#include <stdio.h>#include <stdlib.h> struct list_node {int x; struct list_node *next;};typedef struct list_node node; node * uniq(int *a, unsigned alen) {if (alen == 0) return NULL;  node *start = malloc(sizeof(node));  if (start == NULL) exit(EXIT_FAILURE);  start->x = a;  start->next = NULL;   for (int i = 1 ; i < alen ; ++i)     {node *n = start;      for (;; n = n->next)         {if (a[i] == n->x) break;          if (n->next == NULL)             {n->next = malloc(sizeof(node));              n = n->next;              if (n == NULL) exit(EXIT_FAILURE);              n->x = a[i];              n->next = NULL;              break;}}}   return start;} int main(void)   {int a[] = {1, 2, 1, 4, 5, 2, 15, 1, 3, 4};    for (node *n = uniq(a, 10) ; n != NULL ; n = n->next)        printf("%d ", n->x);    puts("");    return 0;}`
Output:
```1 2 4 5 15 3
```

### O(n^2) version, pure arrays

`#include <stdio.h>#include <stdlib.h>#include <stdbool.h>#include <string.h> /* Returns `true' if element `e' is in array `a'. Otherwise, returns `false'. * Checks only the first `n' elements. Pure, O(n). */bool elem(int *a, size_t n, int e){    for (size_t i = 0; i < n; ++i)        if (a[i] == e)            return true;     return false;} /* Removes the duplicates in array `a' of given length `n'. Returns the number * of unique elements. In-place, order preserving, O(n ^ 2). */size_t nub(int *a, size_t n){    size_t m = 0;     for (size_t i = 0; i < n; ++i)        if (!elem(a, m, a[i]))            a[m++] = a[i];     return m;} /* Out-place version of `nub'. Pure, order preserving, alloc < n * sizeof(int) * bytes, O(n ^ 2). */size_t nub_new(int **b, int *a, size_t n){    int *c = malloc(n * sizeof(int));    memcpy(c, a, n * sizeof(int));    int m = nub(c, n);    *b = malloc(m * sizeof(int));    memcpy(*b, c, m * sizeof(int));    free(c);    return m;} int main(void){    int a[] = {1, 2, 1, 4, 5, 2, 15, 1, 3, 4};    int *b;     size_t n = nub_new(&b, a, sizeof(a) / sizeof(a));     for (size_t i = 0; i < n; ++i)        printf("%d ", b[i]);    puts("");     free(b);    return 0;}`
Output:
```1 2 4 5 15 3
```

### Sorting method

Using qsort and return uniques in-place:
`#include <stdio.h>#include <stdlib.h> int icmp(const void *a, const void *b){#define _I(x) *(const int*)x	return _I(a) < _I(b) ? -1 : _I(a) > _I(b);#undef _I} /* filter items in place and return number of uniques.  if a separate   list is desired, duplicate it before calling this function */int uniq(int *a, int len){	int i, j;	qsort(a, len, sizeof(int), icmp);	for (i = j = 0; i < len; i++)		if (a[i] != a[j]) a[++j] = a[i];	return j + 1;} int main(){	int x[] = {1, 2, 1, 4, 5, 2, 15, 1, 3, 4};	int i, len = uniq(x, sizeof(x) / sizeof(x));	for (i = 0; i < len; i++) printf("%d\n", x[i]); 	return 0;}`
Output:
```1
2
3
4
5
15
```

## C#

Works with: C# version 2+
`int[] nums = { 1, 1, 2, 3, 4, 4 };List<int> unique = new List<int>();foreach (int n in nums)    if (!unique.Contains(n))        unique.Add(n);`
Works with: C# version 3+
`int[] nums = {1, 1, 2, 3, 4, 4};int[] unique = nums.Distinct().ToArray();`

## C++

This version uses std::set, which requires its element type be comparable using the < operator.

`#include <set>#include <iostream>using namespace std; int main() {    typedef set<int> TySet;    int data[] = {1, 2, 3, 2, 3, 4};     TySet unique_set(data, data + 6);     cout << "Set items:" << endl;    for (TySet::iterator iter = unique_set.begin(); iter != unique_set.end(); iter++)          cout << *iter << " ";    cout << endl;}`

This version uses hash_set, which is part of the SGI extension to the Standard Template Library. It is not part of the C++ standard library. It requires that its element type have a hash function.

Works with: GCC
`#include <ext/hash_set>#include <iostream>using namespace std; int main() {    typedef __gnu_cxx::hash_set<int> TyHash;    int data[] = {1, 2, 3, 2, 3, 4};     TyHash unique_set(data, data + 6);     cout << "Set items:" << endl;    for (TyHash::iterator iter = unique_set.begin(); iter != unique_set.end(); iter++)          cout << *iter << " ";    cout << endl;}`

This version uses unordered_set, which is part of the TR1, which is likely to be included in the next version of C++. It is not part of the C++ standard library. It requires that its element type have a hash function.

Works with: GCC
`#include <tr1/unordered_set>#include <iostream>using namespace std; int main() {    typedef tr1::unordered_set<int> TyHash;    int data[] = {1, 2, 3, 2, 3, 4};     TyHash unique_set(data, data + 6);     cout << "Set items:" << endl;    for (TyHash::iterator iter = unique_set.begin(); iter != unique_set.end(); iter++)          cout << *iter << " ";    cout << endl;}`

Alternative method working directly on the array:

`#include <iostream>#include <iterator>#include <algorithm> // helper templatetemplate<typename T> T* end(T (&array)[size]) { return array+size; } int main(){  int data[] = { 1, 2, 3, 2, 3, 4 };  std::sort(data, end(data));  int* new_end = std::unique(data, end(data));  std::copy(data, new_end, std::ostream_iterator<int>(std::cout, " ");  std::cout << std::endl;}`

Using sort, unique, and erase on a vector.

Works with: C++11
`#include <algorithm>#include <iostream>#include <vector> int main() {  std::vector<int> data = {1, 2, 3, 2, 3, 4};   std::sort(data.begin(), data.end());  data.erase(std::unique(data.begin(), data.end()), data.end());   for(int& i: data) std::cout << i << " ";  std::cout << std::endl;  return 0;}`

## CafeOBJ

` -- The parametrized module NO-DUP-LIST(ELEMENTS :: TRIV) defines the signature of simple Haskell like list structure.-- The removal of duplicates is handled by the equational properties listed after the signature in brackets {}-- The binary operation _,_ is associative, commutative, and idempotent.-- This list structure does not permit duplicates, they are removed during evaluation (called reduction in CafeOBJ)-- Actual code is contained in module called  NO-DUP-LIST.-- The tests are performed after opening instantiated NO-DUP-LIST with various concrete types.-- For further details see: http://www.ldl.jaist.ac.jp/cafeobj/mod! NO-DUP-LIST(ELEMENTS :: TRIV)  {    [ List < Elem < Elt]  -- Sorts in Ordered Sorted Algebra    op [] : -> List { prec: 0 }  -- Empty List    op _,_ : Elt Elt -> Elt { comm assoc idem prec: 80 l-assoc }     op [_] : Elt -> List  { prec: 0 }} -- Test on lists of INT, CHARACTER, and STRINGopen NO-DUP-LIST(INT)reduce [ 1 , 2 , 1 , 1 ] .     -- Gives [ 1 , 2 ]open NO-DUP-LIST(CHARACTER)reduce [ 'a' , 'b' , 'a' , 'a' ] .  -- Gives [ 'a' , 'b' ]open NO-DUP-LIST(STRING)reduce [ "abc" , "def" , "abc" ] . -- Gives [ "def" , "abc" ] `

## Ceylon

`<String|Integer>[] data = [1, 2, 3, "a", "b", "c", 2, 3, 4, "b", "c", "d"];<String|Integer>[] unique = HashSet { *data }.sequence();`

## Clojure

`user=> (distinct [1 3 2 9 1 2 3 8 8 1 0 2])(1 3 2 9 8 0)user=>`

## CoffeeScript

Translation of: Kotlin
`data = [ 1, 2, 3, "a", "b", "c", 2, 3, 4, "b", "c", "d" ]set = []set.push i for i in data when not (i in set) console.log dataconsole.log set`
Output:
```[ 1, 2, 3, 'a', 'b', 'c', 2, 3, 4, 'b', 'c', 'd' ]
[ 1, 2, 3, 'a', 'b', 'c', 4, 'd' ]```

## Common Lisp

To remove duplicates non-destructively:

`(remove-duplicates '(1 3 2 9 1 2 3 8 8 1 0 2))> (9 3 8 1 0 2)`

Or, to remove duplicates in-place:

`(delete-duplicates '(1 3 2 9 1 2 3 8 8 1 0 2))> (9 3 8 1 0 2)`

## Crystal

Copied and modified from the Ruby version.

`ary = [1, 1, 2, 2, "a", [1, 2, 3], [1, 2, 3], "a"]p ary.uniq`
`[1, 2, "a", [1, 2, 3]]`

## D

`void main() {    import std.stdio, std.algorithm;     [1, 3, 2, 9, 1, 2, 3, 8, 8, 1, 0, 2]    .sort()    .uniq    .writeln;}`
Output:
`[0, 1, 2, 3, 8, 9]`

Using an associative array:

`void main() {    import std.stdio;     immutable data = [1, 3, 2, 9, 1, 2, 3, 8, 8, 1, 0, 2];     bool[int] hash;    foreach (el; data)        hash[el] = true;    hash.byKey.writeln;}`
Output:
`[8, 0, 1, 9, 2, 3]`

Like code D#1, but with an array returned:

`void main(){    import std.stdio, std.algorithm, std.array;     auto a = [5,4,32,7,6,4,2,6,0,8,6,9].sort.uniq.array;    a.writeln;}`
Output:
`[0, 2, 4, 5, 6, 7, 8, 9, 32]`

## Delphi

`program RemoveDuplicateElements; {\$APPTYPE CONSOLE} uses Generics.Collections; var  i: Integer;  lIntegerList: TList<Integer>;const  INT_ARRAY: array[1..7] of Integer = (1, 2, 2, 3, 4, 5, 5);begin  lIntegerList := TList<Integer>.Create;  try  for i in INT_ARRAY do    if not lIntegerList.Contains(i) then      lIntegerList.Add(i);   for i in lIntegerList do    Writeln(i);  finally    lIntegerList.Free;  end;end.`
Output:
```1
2
3
4
5```

## Déjà Vu

`}for item in [ 1 10 1 :hi :hello :hi :hi ]:	@item!. keys set{`
Output:
`[ 1 :hello 10 :hi ]`

## E

`[1,2,3,2,3,4].asSet().getElements()`

## ECL

` inNumbers   := DATASET([{1},{2},{3},{4},{1},{1},{7},{8},{9},{9},{0},{0},{3},{3},{3},{3},{3}], {INTEGER Field1});DEDUP(SORT(inNumbers,Field1)); `
Output:
```0
1
2
3
4
7
8
9
```

## Elena

ELENA 5.0 :

`import extensions;import system'collections;import system'routines; public program(){    var nums := new int[]{1,1,2,3,4,4};    auto unique := new Map<int, int>();     nums.forEach:(n){ unique[n] := n };     console.printLine(unique.MapValues.asEnumerable())}`
Output:
```1,2,3,4
```

## Elixir

Elixir has an `Enum.uniq` built-in function.

Works with: Elixir version 1.2
`defmodule RC do  # Set approach  def uniq1(list), do: MapSet.new(list) |> MapSet.to_list   # Sort approach  def uniq2(list), do: Enum.sort(list) |> Enum.dedup   # Go through the list approach  def uniq3(list), do: uniq3(list, [])   defp uniq3([], res), do: Enum.reverse(res)  defp uniq3([h|t], res) do    if h in res, do: uniq3(t, res), else: uniq3(t, [h | res])  endend num = 10000max = div(num, 10)list = for _ <- 1..num, do: :rand.uniform(max)funs = [&Enum.uniq/1, &RC.uniq1/1, &RC.uniq2/1, &RC.uniq3/1]Enum.each(funs, fn fun ->  result = fun.([1,1,2,1,'redundant',1.0,[1,2,3],[1,2,3],'redundant',1.0])  :timer.tc(fn ->    Enum.each(1..100, fn _ -> fun.(list) end)  end)  |> fn{t,_} -> IO.puts "#{inspect fun}:\t#{t/1000000}\t#{inspect result}" end.()end)`
Output:
```&Enum.uniq/1:   0.296   [1, 2, 'redundant', 1.0, [1, 2, 3]]
&RC.uniq1/1:    0.686   [1, 2, 1.0, [1, 2, 3], 'redundant']
&RC.uniq2/1:    0.921   [1, 1.0, 2, [1, 2, 3], 'redundant']
&RC.uniq3/1:    1.497   [1, 2, 'redundant', 1.0, [1, 2, 3]]
```

## Erlang

`List = [1, 2, 3, 2, 2, 4, 5, 5, 4, 6, 6, 5].UniqueList = gb_sets:to_list(gb_sets:from_list(List)).% Alternatively the builtin:Unique_list = lists:usort( List ). `

## Euphoria

`include sort.e function uniq(sequence s)    sequence out    s = sort(s)    out = s[1..1]    for i = 2 to length(s) do        if not equal(s[i],out[\$]) then            out = append(out, s[i])        end if    end for    return outend function constant s = {1, 2, 1, 4, 5, 2, 15, 1, 3, 4}? s? uniq(s)`
Output:
```{1,2,1,4,5,2,15,1,3,4}
{1,2,3,4,5,15}
```

## F#

The simplest way is to build a set from the given array (this actually works for any enumerable input sequence type, not just arrays):

` set [|1;2;3;2;3;4|] `

gives:

` val it : Set<int> = seq [1; 2; 3; 4] `

## Factor

`USING: sets ;V{ 1 2 1 3 2 4 5 } members . V{ 1 2 3 4 5 }`

## Forth

Forth has no built-in hashtable facility, so the easiest way to achieve this goal is to take the "uniq" program as an example.

The word uniq, if given a sorted array of cells, will remove the duplicate entries and return the new length of the array. For simplicity, uniq has been written to process cells (which are to Forth what "int" is to C), but could easily be modified to handle a variety of data types through deferred procedures, etc.

The input data is assumed to be sorted.

`\ Increments a2 until it no longer points to the same value as a1\ a3 is the address beyond the data a2 is traversing.: skip-dups ( a1 a2 a3 -- a1 a2+n )    dup rot ?do      over @ i @ <> if drop i leave then    cell +loop ; \ Compress an array of cells by removing adjacent duplicates\ Returns the new count: uniq ( a n -- n2 )   over >r             \ Original addr to return stack   cells over + >r     \ "to" addr now on return stack, available as [email protected]   dup begin           ( write read )      dup [email protected] <   while      2dup @ swap !    \ copy one cell      cell+ [email protected] skip-dups      cell 0 d+        \ increment write ptr only   repeat  r> 2drop  r> - cell / ;`

Here is another implementation of "uniq" that uses a popular parameters and local variables extension words. It is structurally the same as the above implementation, but uses less overt stack manipulation.

`: uniqv { a n \ r e -- n }    a n cells+ to e    a dup to r    \ the write address lives on the stack    begin      r e <    while      r @ over !      r cell+ e skip-dups to r      cell+    repeat    a - cell / ;`

To test this code, you can execute:

`create test 1 , 2 , 3 , 2 , 6 , 4 , 5 , 3 , 6 ,here test - cell / constant ntest: .test ( n -- ) 0 ?do test i cells + ? loop ;  test ntest 2dup cell-sort uniq .test`
Output:
`1 2 3 4 5 6 ok`

## Fortran

Fortran has no built-in hash functions or sorting functions but the code below implements the compare all elements algorithm.

`  program remove_dups  implicit none  integer :: example(12)         ! The input  integer :: res(size(example))  ! The output  integer :: k                   ! The number of unique elements  integer :: i, j   example = [1, 2, 3, 2, 2, 4, 5, 5, 4, 6, 6, 5]  k = 1  res(1) = example(1)  outer: do i=2,size(example)     do j=1,k        if (res(j) == example(i)) then           ! Found a match so start looking again           cycle outer        end if     end do     ! No match found so add it to the output     k = k + 1     res(k) = example(i)  end do outer  write(*,advance='no',fmt='(a,i0,a)') 'Unique list has ',k,' elements: '  write(*,*) res(1:k)end program remove_dups  `

Same as above but using 'ANY' to check if the input number already exists in the array of unique elements:

` program remove_dups    implicit none    integer :: example(12)         ! The input    integer :: res(size(example))  ! The output    integer :: k                   ! The number of unique elements    integer :: i     example = [1, 2, 3, 2, 2, 4, 5, 5, 4, 6, 6, 5]    k = 1    res(1) = example(1)    do i=2,size(example)        ! if the number already exist in res check next        if (any( res == example(i) )) cycle        ! No match found so add it to the output        k = k + 1        res(k) = example(i)    end do     write(*,advance='no',fmt='(a,i0,a)') 'Unique list has ',k,' elements: '    write(*,*) res(1:k)end program remove_dups  `
Output:
`Unique list has 6 elements:            1           2           3           4           5           6`

## FreeBASIC

`' FB 1.05.0 Win64 Sub removeDuplicates(a() As Integer, b() As Integer)  Dim lb As Integer = LBound(a)  Dim ub As Integer = UBound(a)  If ub = -1 Then Return '' empty array  Redim b(lb To ub)  b(lb) = a(lb)  Dim count As Integer = 1  Dim unique As Boolean   For i As Integer = lb + 1 To ub    unique = True     For j As Integer = lb to i - 1      If a(i) = a(j) Then        unique = False        Exit For      End If    Next j    If unique Then      b(lb + count) = a(i)      count += 1    End If  Next i   If count > 0 Then Redim Preserve b(lb To lb + count - 1)  End Sub Dim a(1 To 10) As Integer = {1, 2, 1, 4, 5, 2, 15, 1, 3, 4}Dim b() As IntegerremoveDuplicates a(), b() For i As Integer = LBound(b) To UBound(b)  Print b(i); " ";Next PrintPrint "Press any key to quit"Sleep`
Output:
``` 1  2  4  5  15  3
```

## Frink

The following demonstrates two of the simplest ways of removing duplicates.

` b = [1, 5, 2, 6, 6, 2, 2, 1, 9, 8, 6, 5] // One way, using OrderedList.  An OrderedList is a type of array that keeps// its elements in order.  The items must be comparable.a = new OrderedListprintln[a.insertAllUnique[b]] // Another way, using the "set" datatype and back to an array.println[toArray[toSet[b]] `
Output:
Note that sets are not guaranteed to be printed in any specific order.
```[1, 2, 5, 6, 8, 9]
[9, 8, 6, 5, 2, 1]
```

## Gambas

`Public Sub Main()Dim sString As String[] = Split("Now is the time for all the good men to come to the aid of the good party 1 2 1 3 3 3 2 1 1 2 3 4 33 2 5 4 333 5", " ")Dim sFix As New String[]Dim sTemp As String For Each sTemp In sString  sTemp &= " "  If InStr(sFix.Join(" ") & " ", sTemp) Then Continue  sFix.Add(Trim(sTemp))Next Print sFix.Join(" ") End`

Output:

```Now is the time for all good men to come aid of party 1 2 3 4 33 5 333
```

## GAP

`# Built-in, using sets (which are also lists)a := [ 1, 2, 3, 1, [ 4 ], 5, 5, , 6 ];# [ 1, 2, 3, 1, [ 4 ], 5, 5, [ 4 ], 6 ]b := Set(a);# [ 1, 2, 3, 5, 6, [ 4 ] ]IsSet(b);# trueIsList(b);# true`

## Go

### Map solution

`package main import "fmt" func uniq(list []int) []int {	unique_set := make(map[int]bool, len(list))	for _, x := range list {		unique_set[x] = true	}	result := make([]int, 0, len(unique_set))	for x := range unique_set {		result = append(result, x)	}	return result} func main() {	fmt.Println(uniq([]int{1, 2, 3, 2, 3, 4})) // prints: [3 4 1 2] (but in a semi-random order)}`

### Map preserving order

It takes only small changes to the above code to preserver order. Just store the sequence in the map:

`package main import "fmt" func uniq(list []int) []int {	unique_set := make(map[int]int, len(list))	i := 0	for _, x := range list {		if _, there := unique_set[x]; !there {			unique_set[x] = i			i++		}	}	result := make([]int, len(unique_set))	for x, i := range unique_set {		result[i] = x	}	return result} func main() {	fmt.Println(uniq([]int{1, 2, 3, 2, 3, 4})) // prints: [1 2 3 4]}`

### Float64, removing duplicate NaNs

In solutions above, you just replace `int` with another type to use for a list of another type. (See Associative_arrays/Creation#Go for acceptable types.) Except a weird thing happens with NaNs. They (correctly) don't compare equal, so you have to special case them if you want to remove duplicate NaNs:

`package main import (	"fmt"	"math") func uniq(list []float64) []float64 {	unique_set := map[float64]int{}	i := 0	nan := false	for _, x := range list {		if _, exists := unique_set[x]; exists {			continue		}		if math.IsNaN(x) {			if nan {				continue			} else {				nan = true			}		}		unique_set[x] = i		i++	}	result := make([]float64, len(unique_set))	for x, i := range unique_set {		result[i] = x	}	return result} func main() {	fmt.Println(uniq([]float64{1, 2, math.NaN(), 2, math.NaN(), 4})) // Prints [1 2 NaN 4]}`

### Any type using reflection

Go doesn't have templates or generics, but it does have reflection. Using this it's possible to build a version that will work on almost any array or slice type. Using the reflect package for this does make the code less readable.

Normally in Go this type of solution is somewhat rare. Instead, for very short code (such as min, max, abs) it's common to cast or make a type specific function by hand as needed. For longer code, often an interface can be used instead (see the `sort` package for an example).

Note: due to details with how Go handles map keys that contain a NaN somewhere (including within a complex or even within a sub struct field) this version simply omits any NaN containing values it comes across and returns a bool to indicate if that happened. This version is otherwise a translation of the above order preserving map implementation, it does not for example call reflect.DeepEqual so elements with pointers to distinct but equal values will be treated as non-equal.

`package main import (	"fmt"	"math"	"reflect") func uniq(x interface{}) (interface{}, bool) {	v := reflect.ValueOf(x)	if !v.IsValid() {		panic("uniq: invalid argument")	}	if k := v.Kind(); k != reflect.Array && k != reflect.Slice {		panic("uniq: argument must be an array or a slice")	}	elemType := v.Type().Elem()	intType := reflect.TypeOf(int(0))	mapType := reflect.MapOf(elemType, intType)	m := reflect.MakeMap(mapType)	i := 0	for j := 0; j < v.Len(); j++ {		x := v.Index(j)		if m.MapIndex(x).IsValid() {			continue		}		m.SetMapIndex(x, reflect.ValueOf(i))		if m.MapIndex(x).IsValid() {			i++		}	}	sliceType := reflect.SliceOf(elemType)	result := reflect.MakeSlice(sliceType, i, i)	hadNaN := false	for _, key := range m.MapKeys() {		ival := m.MapIndex(key)		if !ival.IsValid() {			hadNaN = true		} else {			result.Index(int(ival.Int())).Set(key)		}	} 	return result.Interface(), hadNaN} type MyType struct {	name  string	value float32} func main() {	intArray := [...]int{5, 1, 2, 3, 2, 3, 4}	intSlice := []int{5, 1, 2, 3, 2, 3, 4}	stringSlice := []string{"five", "one", "two", "three", "two", "three", "four"}	floats := []float64{1, 2, 2, 4,		math.NaN(), 2, math.NaN(),		math.Inf(1), math.Inf(1), math.Inf(-1), math.Inf(-1)}	complexes := []complex128{1, 1i, 1 + 1i, 1 + 1i,		complex(math.NaN(), 1), complex(1, math.NaN()),		complex(math.Inf(+1), 1), complex(1, math.Inf(1)),		complex(math.Inf(-1), 1), complex(1, math.Inf(1)),	}	structs := []MyType{		{"foo", 42},		{"foo", 2},		{"foo", 42},		{"bar", 42},		{"bar", 2},		{"fail", float32(math.NaN())},	} 	fmt.Print("intArray: ", intArray, " → ")	fmt.Println(uniq(intArray))	fmt.Print("intSlice: ", intSlice, " → ")	fmt.Println(uniq(intSlice))	fmt.Print("stringSlice: ", stringSlice, " → ")	fmt.Println(uniq(stringSlice))	fmt.Print("floats: ", floats, " → ")	fmt.Println(uniq(floats))	fmt.Print("complexes: ", complexes, "\n → ")	fmt.Println(uniq(complexes))	fmt.Print("structs: ", structs, " → ")	fmt.Println(uniq(structs))	// Passing a non slice or array will compile put	// then produce a run time panic:	//a := 42	//uniq(a)	//uniq(nil)}`
Output:
```intArray: [5 1 2 3 2 3 4] → [5 1 2 3 4] false
intSlice: [5 1 2 3 2 3 4] → [5 1 2 3 4] false
stringSlice: [five one two three two three four] → [five one two three four] false
floats: [1 2 2 4 NaN 2 NaN +Inf +Inf -Inf -Inf] → [1 2 4 +Inf -Inf] true
complexes: [(1+0i) (0+1i) (1+1i) (1+1i) (NaN+1i) (1+NaNi) (+Inf+1i) (1+Infi) (-Inf+1i) (1+Infi)]
→ [(1+0i) (0+1i) (1+1i) (+Inf+1i) (1+Infi) (-Inf+1i)] true
structs: [{foo 42} {foo 2} {foo 42} {bar 42} {bar 2} {fail NaN}] → [{foo 42} {foo 2} {bar 42} {bar 2}] true
```

## Groovy

`def list = [1, 2, 3, 'a', 'b', 'c', 2, 3, 4, 'b', 'c', 'd']assert list.size() == 12println "             Original List: \${list}" // Filtering the List (non-mutating)def list2 = list.unique(false)assert list2.size() == 8assert list.size() == 12println "             Filtered List: \${list2}" // Filtering the List (in place)list.unique()assert list.size() == 8println "   Original List, filtered: \${list}" def list3 = [1, 2, 3, 'a', 'b', 'c', 2, 3, 4, 'b', 'c', 'd']assert list3.size() == 12 // Converting to Setdef set = list as Setassert set.size() == 8println "                       Set: \${set}"`
Output:
```             Original List: [1, 2, 3, a, b, c, 2, 3, 4, b, c, d]
Filtered List: [1, 2, 3, a, b, c, 4, d]
Original List, filtered: [1, 2, 3, a, b, c, 4, d]
Set: [1, 2, 3, a, b, c, 4, d]```

## GW-BASIC

Translation of: Modula-2
Works with: PC-BASIC version any
`10   ' Remove Duplicates20   OPTION BASE 130   LET MAXI% = 740   DIM D(7), R(7): ' data, result50   ' Set the data.60   FOR I% = 1 TO 770    READ D(I%)80   NEXT I%90   ' Remove duplicates.   100  LET R(1) = D(1)110  LET LRI% = 1: ' last index of result120  LET P% = 1: ' position130  WHILE P% < MAXI%140   LET P% = P% + 1150   LET ISNEW = 1: ' is a new number?160   LET RI% = 1: ' current index of result170   WHILE (RI% <= LRI%) AND ISNEW180    IF D(P%) = R(RI%) THEN LET ISNEW = 0190    LET RI% = RI% + 1200   WEND210   IF ISNEW THEN LET LRI% = LRI% + 1: LET R(LRI%) = D(P%)220  WEND230  FOR RI% = 1 TO LRI%240   PRINT R(RI%)250  NEXT RI%260  END1000 DATA 1, 2, 2, 3, 4, 5, 5 `
Output:
```1
2
3
4
5
```

### Usage

` print \$ unique [4, 5, 4, 2, 3, 3, 4] [4,5,2,3]`

### Sorted result using Set

O(n ln(n)). Requires there is a partial ordering of elements.

`import qualified Data.Set as Set unique :: Ord a => [a] -> [a]unique = Set.toList . Set.fromList`

### Unsorted result using Set

O(n ln(n)). Retains original order. Requires there is a partial ordering of elements.

`import Data.Set unique :: Ord a => [a] -> [a]unique = loop empty  where    loop s []                    = []    loop s (x : xs) | member x s = loop s xs                    | otherwise  = x : loop (insert x s) xs`

### Using filter

O(n^2). Retains original order. Only requires that elements can be compared for equality.

`import Data.List unique :: Eq a => [a] -> [a]unique []       = []unique (x : xs) = x : unique (filter (x /=) xs)`

### Standard Library

`import Data.ListData.List.nub :: Eq a => [a] -> [a]Data.List.Unique.unique :: Ord a => [a] -> [a]`

## HicEst

`REAL ::      nums(12)CHARACTER :: workspace*100 nums = (1, 3, 2, 9, 1, 2, 3, 8, 8, 1, 0, 2)WRITE(Text=workspace) nums                   ! convert to stringEDIT(Text=workspace, SortDelDbls=workspace)  ! do the job for a stringREAD(Text=workspace, ItemS=individuals) nums ! convert to numeric WRITE(ClipBoard) individuals, "individuals: ", nums ! 6 individuals: 0 1 2 3 8 9 0 0 0 0 0 0 `

## Icon and Unicon

This solution preserves the original order of the elements.

`procedure main(args)    every write(!noDups(args))end procedure noDups(L)    every put(newL := [], notDup(set(),!L))    return newLend procedure notDup(cache, a)    if not member(cache, a) then {         insert(cache, a)         return a         }end`

A sample run is:

```->noDups a b c d c a b e
a
b
c
d
e
->
```

## IDL

`non_repeated_values = array[uniq(array, sort( array))]`

## Inform 7

`To decide which list of Ks is (L - list of values of kind K) without duplicates:	let result be a list of Ks;	repeat with X running through L:		add X to result, if absent;	decide on result.`

## IS-BASIC

`100 PROGRAM "RemoveDu.bas"110 RANDOMIZE120 NUMERIC ARR(1 TO 20),TOP130 LET TOP=FILL(ARR)140 CALL WRITE(ARR,TOP)150 LET TOP=REMOVE(ARR)160 CALL WRITE(ARR,TOP)170 DEF WRITE(REF A,N)180   FOR I=1 TO N190     PRINT A(I);200   NEXT210   PRINT220 END DEF230 DEF FILL(REF A)240   LET FILL=UBOUND(A):LET A(LBOUND(A))=1250   FOR I=LBOUND(A)+1 TO UBOUND(A)260     LET A(I)=A(I-1)+RND(3)270   NEXT280 END DEF 290 DEF REMOVE(REF A)300   LET ST=0310   FOR I=LBOUND(A)+1 TO UBOUND(A)320     IF A(I-1)=A(I) THEN LET ST=ST+1330     IF ST>0 THEN LET A(I-ST)=A(I)340   NEXT 350   LET REMOVE=UBOUND(A)-ST360 END DEF`
Output:
```START
1  1  2  4  5  7  9  10  12  14  16  16  16  17  18  20  20  22  23  23
1  2  4  5  7  9  10  12  14  16  17  18  20  22  23
ok
START
1  2  4  5  5  5  7  8  9  9  10  10  10  12  14  15  17  17  18  20
1  2  4  5  7  8  9  10  12  14  15  17  18  20
ok
START
1  3  3  4  5  6  8  10  11  12  14  16  16  16  16  18  18  19  21  21
1  3  4  5  6  8  10  11  12  14  16  18  19  21
ok
START
1  3  3  4  5  5  7  9  11  13  13  14  16  17  17  18  19  19  20  21
1  3  4  5  7  9  11  13  14  16  17  18  19  20  21
ok
START
1  2  3  5  5  6  6  7  8  10  12  14  15  17  17  19  21  23  25  25
1  2  3  5  6  7  8  10  12  14  15  17  19  21  23  25
ok```

## J

The verb` ~. `removes duplicate items from any array (numeric, character, or other; vector, matrix, rank-n array). For example:

`   ~. 4 3 2 8 0 1 9 5 1 7 6 3 9 9 4 2 1 5 3 2  4 3 2 8 0 1 9 5 7 6   ~. 'chthonic eleemosynary paronomasiac'chtoni elmsyarp`

Or (since J defines an item of an n dimensional array as its n-1 dimensional sub arrays):

`   0 1 1 2 0 */0 1 20 0 00 1 20 1 20 2 40 0 0   ~. 0 1 1 2 0 */0 1 20 0 00 1 20 2 4`

## Java

Works with: Java version 1.5
`import java.util.*; class Test {     public static void main(String[] args) {         Object[] data = {1, 1, 2, 2, 3, 3, 3, "a", "a", "b", "b", "c", "d"};        Set<Object> uniqueSet = new HashSet<Object>(Arrays.asList(data));        for (Object o : uniqueSet)            System.out.printf("%s ", o);    }}`
`1 a 2 b 3 c d`
Works with: Java version 8
`import java.util.*; class Test {     public static void main(String[] args) {         Object[] data = {1, 1, 2, 2, 3, 3, 3, "a", "a", "b", "b", "c", "d"};        Arrays.stream(data).distinct().forEach((o) -> System.out.printf("%s ", o));    }}`
`1 2 3 a b c d`

## JavaScript

This uses the `===` "strict equality" operator, which does no type conversions (`4 == "4"` is true but `4 === "4"` is false)

`function unique(ary) {    // concat() with no args is a way to clone an array    var u = ary.concat().sort();    for (var i = 1; i < u.length; ) {        if (u[i-1] === u[i])            u.splice(i,1);        else            i++;    }    return u;} var ary = [1, 2, 3, "a", "b", "c", 2, 3, 4, "b", "c", "d", "4"];var uniq = unique(ary);for (var i = 0; i < uniq.length; i++)     print(uniq[i] + "\t" + typeof(uniq[i]));`
```1 - number
2 - number
3 - number
4 - number
4 - string
a - string
b - string
c - string
d - string```

Or, extend the prototype for Array:

`Array.prototype.unique = function() {    var u = this.concat().sort();    for (var i = 1; i < u.length; ) {        if (u[i-1] === u[i])            u.splice(i,1);        else            i++;    }    return u;}var uniq = [1, 2, 3, "a", "b", "c", 2, 3, 4, "b", "c", "d"].unique();`

With reduce and arrow functions (ES6):

`Array.prototype.unique = function() {   return this.sort().reduce( (a,e) => e === a[a.length-1] ? a : (a.push(e), a), [] )}`

With sets and spread operator (ES6):

`Array.prototype.unique = function() {    return [... new Set(this)]}`

If, however, the array is homogenous, or we wish to interpret it as such by using JavaScript's Abstract Equality comparison (as in '==', see http://www.ecma-international.org/ecma-262/5.1/#sec-11.9.3) then it proves significantly faster to use a hash table.

For example, in ES 5:

`function uniq(lst) {  var u = [],    dct = {},    i = lst.length,    v;   while (i--) {    v = lst[i], dct[v] || (      dct[v] = u.push(v)    );  }  u.sort(); // optional   return u;}`

Or, to allow for customised definitions of equality and duplication, we can follow the Haskell prelude in defining a nub :: [a] -> [a] function which is a special case of nubBy :: (a -> a -> Bool) -> [a] -> [a]

`(function () {    'use strict';     // nub :: [a] -> [a]    function nub(xs) {         // Eq :: a -> a -> Bool        function Eq(a, b) {            return a === b;        }         // nubBy :: (a -> a -> Bool) -> [a] -> [a]        function nubBy(fnEq, xs) {            var x = xs.length ? xs : undefined;             return x !== undefined ? [x].concat(                nubBy(fnEq, xs.slice(1)                    .filter(function (y) {                        return !fnEq(x, y);                    }))            ) : [];        }         return nubBy(Eq, xs);    }      // TEST     return [        nub('4 3 2 8 0 1 9 5 1 7 6 3 9 9 4 2 1 5 3 2'.split(' '))        .map(function (x) {            return Number(x);        }),        nub('chthonic eleemosynary paronomasiac'.split(''))        .join('')    ] })();`
Output:
`[[4, 3, 2, 8, 0, 1, 9, 5, 7, 6], "chtoni elmsyarp"]`

## jq

If it is acceptable to alter the ordering of elements, then the builtin (fast) filter, unique, can be used. It can be used for arrays with elements of any JSON type and returns the distinct elements in sorted order.

`[4,3,2,1,1,2,3,4] | unique`

If all but the first occurrence of each element should be deleted, then the following function could be used. It retains the advantage of imposing no restrictions on the types of elements in the array and for that reason is slightly more complex than would otherwise be required.

`def removeAllButFirst:   # The hash table functions all expect the hash table to be the input.   # Is x in the hash table?  def hashed(x):    (x|tostring) as \$value    | .[\$value] as \$bucket    | \$bucket and (.[\$value] | index([x]));   # Add x to the hash table:  def add_hash(x):    (x|tostring) as \$value    | .[\$value] as \$bucket    | if \$bucket and (\$bucket | index([x])) then .      else .[\$value] += [x]      end;   reduce .[] as \$item    ( [[], {}]; # [array, hash]      if . | hashed(\$item) then .      else [ (. + [\$item]), (. | add_hash(\$item)) ]      end)  | .;  `

## Julia

Works with: Julia version 0.6
`a = [1, 2, 3, 4, 1, 2, 3, 4]@show unique(a) Set(a)`
Output:
```unique(a) = [1, 2, 3, 4]
Set(a) = Set([4, 2, 3, 1])```

## K

(Inspired by the J version.)

`   a:4 5#20?13   / create a random 4 x 5 matrix(12 7 12 4 3 6 3 7 4 7 3 8 3 1 2 2 12 6 4 1)    ,/a           / flatten to array12 7 12 4 3 6 3 7 4 7 3 8 3 1 2 2 12 6 4 1    ?,/a          / distinct elements12 7 4 3 6 8 1 2    ?"chthonic eleemosynary paronomasiac""chtoni elmsyarp"    ?("this";"that";"was";"that";"was";"this")("this" "that" "was")    0 1 1 2 0 *\: 0 1 2(0 0 0 0 1 2 0 1 2 0 2 4 0 0 0)    ?0 1 1 2 0 *\: 0 1 2(0 0 0 0 1 2 0 2 4)`

## Kotlin

Translation of: Java
`fun main(args: Array<String>) {    val data = listOf(1, 2, 3, "a", "b", "c", 2, 3, 4, "b", "c", "d")    val set = data.distinct()     println(data)    println(set)}`
Output:
```[1, 2, 3, a, b, c, 2, 3, 4, b, c, d]
[1, 2, 3, a, b, c, 4, d]```

## Lang5

`: dip  swap '_ set execute _ ; : remove-duplicates    [] swap do unique? length 0 == if break then loop drop ;: unique?    0 extract swap "2dup in if drop else append then" dip ; [1 2 6 3 6 4 5 6] remove-duplicates .`

Built-in function:

`[1 2 6 3 6 4 5 6] 's distinct[1 2 6 3 6 4 5 6] 's dress dup union .`

## Lasso

`local(	x = array(3,4,8,1,8,1,4,5,6,8,9,6),	y = array)with n in #x where #y !>> #n do => { #y->insert(#n) }// result: array(3, 4, 8, 1, 5, 6, 9)`

## Liberty BASIC

LB has arrays, but here the elements are stored in a space-separated string.

` a\$ =" 1 \$23.19 2 elbow 3 2 Bork 4 3 elbow 2 \$23.19 "print "Original set of elements = ["; a\$; "]" b\$ =removeDuplicates\$( a\$)print "With duplicates removed  = ["; b\$; "]" end function removeDuplicates\$( in\$)    o\$ =" "    i  =1    do        term\$    =word\$( in\$, i, " ")        if instr( o\$, " "; term\$; " ") =0 and term\$ <>" " then o\$ =o\$ +term\$ +" "        i        =i +1    loop until term\$ =""    removeDuplicates\$ =o\$end function `
```Original set of elements = [ 1 \$23.19 2 elbow 3 2 Bork 4 3 elbow 2 \$23.19 ]
With duplicates removed  = [ 1 \$23.19 2 elbow 3 Bork 4  ]
```

## Logo

Works with: UCB Logo
`show remdup [1 2 3 a b c 2 3 4 b c d]   ; [1 a 2 3 4 b c d]`

## Lua

`items = {1,2,3,4,1,2,3,4,"bird","cat","dog","dog","bird"}flags = {}io.write('Unique items are:')for i=1,#items do   if not flags[items[i]] then      io.write(' ' .. items[i])      flags[items[i]] = true   endendio.write('\n')`
Output:
`Unique items are: 1 2 3 4 bird cat dog`

Lua doesn't accept Not-a-Number (NaN) and nil as table key, we can handle them like this (Lua 5.3):

`local items = {1,2,3,4,1,2,3,4,0/0,nil,"bird","cat","dog","dog","bird",0/0} function rmdup(t)  local r,dup,c,NaN = {},{},1,{}    for i=1,#t do     local e = t[i]    local k = e~=e and NaN or e    if k~=nil and not dup[k] then        c, r[c], dup[k]= c+1, e, true     end  end  return rend print(table.concat(rmdup(items),' '))`
Output:
`1 2 3 4 nan bird cat dog`

## Maple

This is simplest with a list, which is an immutable array.

`> L := [ 1, 2, 1, 2, 3, 3, 2, 1, "a", "b", "b", "a", "c", "b" ];      L := [1, 2, 1, 2, 3, 3, 2, 1, "a", "b", "b", "a", "c", "b"] > [op]({op}(L));                        [1, 2, 3, "a", "b", "c"]`

That is idiomatic, but perhaps a bit cryptic; here is a more verbose equivalent:

`> convert( convert( L, 'set' ), 'list' );                        [1, 2, 3, "a", "b", "c"]`

For an Array, which is mutable, the table solution works well in Maple.

`> A := Array( L ):> for u in A do T[u] := 1 end: Array( [indices]( T, 'nolist' ) );                        [1, 2, 3, "c", "a", "b"]`

Note that the output (due to the Array() constructor) is in fact an Array.

## Mathematica

Built-in function:

`DeleteDuplicates[{0, 2, 1, 4, 2, 0, 3, 1, 1, 1, 0, 3}]`

gives back:

`{0, 2, 1, 4, 3}`

Delete duplicates and return sorted elements:

` Union[{0, 2, 1, 4, 2, 0, 3, 1, 1, 1, 0, 3}]`
gives back
:
`{0, 1, 2, 3, 4}`

## MATLAB

MATLAB has a built-in function, "unique(list)", which performs this task.
Sample Usage:

`>> unique([1 2 6 3 6 4 5 6]) ans =      1     2     3     4     5     6`

NOTE: The unique function only works for vectors and not for true arrays.

## Maxima

`unique([8, 9, 5, 2, 0, 7, 0, 0, 4, 2, 7, 3, 9, 6, 6, 2, 4, 7, 9, 8, 3, 8, 0, 3, 7, 0, 2, 7, 6, 0]);[0, 2, 3, 4, 5, 6, 7, 8, 9]`

## MAXScript

`uniques = #(1, 2, 3, "a", "b", "c", 2, 3, 4, "b", "c", "d")for i in uniques.count to 1 by -1 do(    id = findItem uniques uniques[i]    if (id != i) do deleteItem uniques i)`

## Microsoft Small Basic

Translation of: Modula-2
` ' Set the data.dataArray = 1dataArray = 2dataArray = 2dataArray = 3dataArray = 4dataArray = 5dataArray = 5 resultArray = dataArraylastResultIndex = 1position = 1While position < Array.GetItemCount(dataArray)  position = position + 1  isNewNumber = 1 ' logical 1  resultIndex = 1  While (resultIndex <= lastResultIndex) And isNewNumber = 1    If dataArray[position] = resultArray[resultIndex] Then      isNewNumber = 0    EndIf    resultIndex = resultIndex + 1  EndWhile  If isNewNumber = 1 Then    lastResultIndex = lastResultIndex + 1    resultArray[lastResultIndex] = dataArray[position]  EndIfEndWhileFor resultIndex = 1 To lastResultIndex  TextWindow.WriteLine(resultArray[resultIndex])EndFor `

## MiniScript

`items = [1, 2, 3, "a", "b", "c", 2, 3, 4, "b", "c", "d"]d = {}for i in items    d.push iend forprint d.indexes`
Output:
`["b", 1, "d", 3, "a", 4, "c", 2]`

## ML

### mLite

A bit like option 3, except copying each element as encountered, and checking to see if it has already been encountered

`fun mem (x, []) = false      | (x eql a, a :: as) = true      | (x, _ :: as) = mem (x, as);	  fun remdup		([], uniq) = rev uniq	|	(h :: t, uniq) = if mem(h, uniq) then				remdup (t, uniq)			else				remdup (t, h :: uniq)	|	L =	remdup (L, []) ;	println ` implode ` remdup ` explode "the quick brown fox jumped over the lazy dog";println ` remdup [1,2,3,4,4,3,2,1, "dog","cat","dog", 1.1, 2.2, 3.3, 1.1]; `
Output:
```the quickbrownfxjmpdvlazyg
[1, 2, 3, 4, dog, cat, 1.1, 2.2, 3.3]```

## Modula-2

Works with: ADW Modula-2 version any (Compile with the linker option Console Application).
` MODULE RemoveDuplicates; FROM STextIO IMPORT  WriteLn;FROM SWholeIO IMPORT  WriteInt; TYPE  TArrayRange = [1 .. 7];  TArray = ARRAY TArrayRange OF INTEGER; VAR  DataArray, ResultArray: TArray;  ResultIndex, LastResultIndex, Position: CARDINAL;  IsNewNumber: BOOLEAN; BEGIN  (* Set the data. *);  DataArray := 1;  DataArray := 2;  DataArray := 2;  DataArray := 3;  DataArray := 4;  DataArray := 5;  DataArray := 5;   ResultArray := DataArray;  LastResultIndex := 1;  Position := 1;  WHILE Position < HIGH(DataArray) DO    INC(Position);    IsNewNumber := TRUE;    ResultIndex := 1;    WHILE (ResultIndex <= LastResultIndex) AND IsNewNumber DO      IF DataArray[Position] = ResultArray[ResultIndex] THEN        IsNewNumber := FALSE;      END;      INC(ResultIndex);    END;    IF IsNewNumber THEN      INC(LastResultIndex);      ResultArray[LastResultIndex] := DataArray[Position];    END  END;  FOR ResultIndex := 1 TO LastResultIndex DO    WriteInt(ResultArray[ResultIndex], 1);    WriteLn;  END;END RemoveDuplicates. `

## MUMPS

We'll take advantage of the fact that an array can only have one index of any specific value. Sorting into canonical order is a side effect. If the indices are strings containing the separator string, they'll be split apart.

`REMDUPE(L,S) ;L is the input listing ;S is the separator between entries ;R is the list to be returned NEW Z,I,R FOR I=1:1:\$LENGTH(L,S) SET Z(\$PIECE(L,S,I))="" ;Repack for return SET I="",R="" FOR  SET I=\$O(Z(I)) QUIT:I=""  SET R=\$SELECT(\$L(R)=0:I,1:R_S_I) KILL Z,I QUIT R`
Example:
```USER>W \$\$REMDUPE^ROSETTA("1,2,3,4,5,2,5,""HELLO"",42,""WORLD""",",")
1,2,3,4,5,42,"HELLO","WORLD"```

## Nanoquery

After executing, the list 'unique' will contain only the unique items.

`items   = {1, 2, 3, "a", "b", "c", 2, 3, 4, "b", "c", "d"}unique  = {} for item in items    if not item in unique        unique.append(item)    endend`

## Neko

`/** Remove duplicate elements, in Neko*/ var original = \$array(1, 2, 1, 4, 5, 2, 15, 1, 3, 4) /* Create a table with only unique elements from the array */var dedup = function(a) {    var size = \$asize(a)    var hash = \$hnew(size)    while size > 0 {        var v = a[size - 1]        var k = \$hkey(v)        \$hset(hash, k, v, null)        size -= 1    }    return hash} /* Show the original list and the unique values */\$print(original, "\n")var show = function(k, v) \$print(v, " ")\$hiter(dedup(original), show)\$print("\n")`
Output:
```prompt\$ nekoc remove-duplicates.neko
prompt\$ neko remove-duplicates.n
[1,2,1,4,5,2,15,1,3,4]
1 2 3 4 5 15```

## Nemerle

`using System.Console; module RemDups{    Main() : void    {        def nums = array[1, 4, 6, 3, 6, 2, 7, 2, 5, 2, 6, 8];        def unique = \$[n | n in nums].RemoveDuplicates();        WriteLine(unique);    }}`

## NetRexx

This sample takes advantage of the NetRexx built-in Rexx object's indexed string capability (associative arrays). Rexx indexed strings act very like hash tables:

`/* NetRexx */options replace format comments java crossref symbols nobinary -- Note: Task requirement is to process "arrays".  The following converts arrays into simple lists of words:--       Putting the resulting list back into an array is left as an exercise for the reader.a1 = [2, 3, 5, 7, 11, 13, 17, 19, 'cats', 222, -100.2, +11, 1.1, +7, '7.', 7, 5, 5, 3, 2, 0, 4.4, 2]a2 = [1, 2, 3, 'a', 'b', 'c', 2, 3, 4, 'b', 'c', 'd']a3 = ['Now', 'is', 'the', 'time', 'for', 'all', 'good', 'men', 'to', 'come', 'to', 'the', 'aid', 'of', 'the', 'party.']x = 0lists = ''x = x + 1; lists = x; lists[x] = array2wordlist(a1)x = x + 1; lists = x; lists[x] = array2wordlist(a2)x = x + 1; lists = x; lists[x] = array2wordlist(a3) loop ix = 1 to lists  nodups_list = remove_dups(lists[ix])  say ix.right(4)':' lists[ix]  say ''.right(4)':' nodups_list  say  end ix return -- =============================================================================method remove_dups(list) public static   newlist = ''  nodups = '0'  loop w_ = 1 to list.words()    ix = list.word(w_)    nodups[ix] = nodups[ix] + 1 -- we can even collect a count of dups if we want    end w_  loop k_ over nodups    newlist = newlist k_    end k_   return newlist.space -- =============================================================================method array2wordlist(ra = Rexx[]) public static   wordlist = ''  loop r_ over ra    wordlist = wordlist r_    end r_   return wordlist.space `
Output:
```   1: 2 3 5 7 11 13 17 19 cats 222 -100.2 11 1.1 7 7. 7 5 5 3 2 0 4.4 2
: 13 2 3 17 19 7. 4.4 5 222 7 -100.2 1.1 cats 0 11

2: 1 2 3 a b c 2 3 4 b c d
: c 2 d 3 4 a b 1

3: Now is the time for all good men to come to the aid of the party.
: Now aid for men to the party. come time of is all good
```

## NewLISP

`(unique '(1 2 3 a b c 2 3 4 b c d))`

## Nial

`uniques := [1, 2, 3, 'a', 'b', 'c', 2, 3, 4, 'b', 'c', 'd']cull uniques=+-+-+-+-+-+-+-+-+=|1|2|3|a|b|c|4|d|=+-+-+-+-+-+-+-+-+`

Using strand form

`cull 1 1 2 2 3 3=1 2 3`

## Nim

`import sequtils, algorithm, intsets # Go through the list, and for each element, check the rest of the list to see# if it appears again,var items = @[1, 2, 3, 2, 3, 4, 5, 6, 7]echo deduplicate(items) # O(n^2) proc filterDup(xs): seq[int] =  result = @[xs]  var last = xs  for x in xs[1..xs.high]:    if x != last:      result.add(x)      last = x #  Put the elements into a hash table which does not allow duplicates.var s = initIntSet()for x in items:  s.incl(x)echo s # Sort the elements and remove consecutive duplicate elements.sort(items, system.cmp[int]) # O(n log n)echo filterDup(items) # O(n)`

## Objeck

` use Structure; bundle Default {  class Unique {    function : Main(args : String[]) ~ Nil {      nums := [1, 1, 2, 3, 4, 4];      unique := IntVector->New();       each(i : nums) {        n := nums[i];        if(unique->Has(n) = false) {          unique->AddBack(n);        };      };       each(i : unique) {        unique->Get(i)->PrintLine();      };    }  }} `

## Objective-C

`NSArray *items = [NSArray arrayWithObjects:@"A", @"B", @"C", @"B", @"A", nil]; NSSet *unique = [NSSet setWithArray:items];`

## OCaml

`let uniq lst =  let unique_set = Hashtbl.create (List.length lst) in  List.iter (fun x -> Hashtbl.replace unique_set x ()) lst;  Hashtbl.fold (fun x () xs -> x :: xs) unique_set [] let _ =  uniq [1;2;3;2;3;4]`

Another solution (preserves order of first occurrence):

`let uniq lst =  let seen = Hashtbl.create (List.length lst) in  List.filter (fun x -> let tmp = not (Hashtbl.mem seen x) in                        Hashtbl.replace seen x ();                        tmp) lst let _ =  uniq [1;2;3;2;3;4]`

Solution reversing list order :

`let uniq l =  let rec tail_uniq a l =    match l with      | [] -> a      | hd::tl -> tail_uniq (hd::a) (List.filter (fun x -> x  != hd) tl) in  tail_uniq [] l`
Works with: OCaml version 4.02+
`List.sort_uniq compare [1;2;3;2;3;4]`

## Octave

` input=[1 2 6 4 2 32 5 5 4 3 3 5 1  2 32 4 4];output=unique(input); `

## Oforth

The list is converted to a set to remove duplicate elements

Output:
```import: set

[ 1, 2, 3, 1, 2, 4, 1, 3, 4, 5 ] asSet println
[1, 2, 3, 4, 5]
```

## ooRexx

`data = .array~of(1, 2, 3, "a", "b", "c", 2, 3, 4, "b", "c", "d")uniqueData = .set~new~union(data)~makearray~sort say "Unique elements are"saydo item over uniqueData   say itemend`
Output:
```Unique elements are

1
2
3
4
a
b
c
d```

## Oz

The following solutions only works if the value type is allowed as a key in a dictionary.

`declare   fun {Nub Xs}     D = {Dictionary.new}  in     for X in Xs do D.X := unit end     {Dictionary.keys D}  end in   {Show {Nub [1 2 1 3 5 4 3 4 4]}}`

## PARI/GP

Sort and remove duplicates. Other methods should be implemented as well.

`rd(v)={  vecsort(v,,8)};`

## Pascal

`Program RemoveDuplicates; const  iArray: array[1..7] of integer = (1, 2, 2, 3, 4, 5, 5); var  rArray: array[1..7] of integer;  i, pos, last: integer;  newNumber: boolean; begin  rArray := iArray;  last := 1;  pos := 1;  while pos < high(iArray) do  begin    inc(pos);    newNumber := true;    for i := low(rArray) to last do      if iArray[pos] = rArray[i] then      begin        newNumber := false;	break;      end;    if newNumber then    begin      inc(last);      rArray[last] := iArray[pos];    end;  end;  for i := low(rArray) to last do    writeln (rArray[i]);end.`
Output:
```% ./RemoveDuplicates
1
2
3
4
5```

## Perl

(this version even preserves the order of first appearance of each element)

`use List::MoreUtils qw(uniq); my @uniq = uniq qw(1 2 3 a b c 2 3 4 b c d);`

It is implemented like this:

`my %seen;my @uniq = grep {!\$seen{\$_}++} qw(1 2 3 a b c 2 3 4 b c d);`

Note: the following two solutions convert elements to strings in the result, so if you give it references they will lose the ability to be dereferenced.

Alternately:

`my %hash = map { \$_ => 1 } qw(1 2 3 a b c 2 3 4 b c d);my @uniq = keys %hash;`

Alternately:

`my %seen;@seen{qw(1 2 3 a b c 2 3 4 b c d)} = ();my @uniq = keys %seen;`

## Phix

Preserves order of first occurence. Applies to any data type. Should be pretty efficient, as the tagsort is O(n log n), then there are two O(n) loops.

`sequence test function alpha(integer i, integer j)integer res    res = compare(test[i],test[j])    if res=0 then        res = compare(i,j)    end if    return resend function function unique(sequence s)sequence at, valid = repeat(1,length(s))object last, thisinteger ai, nxt     test = s    at = custom_sort(routine_id("alpha"),tagset(length(test)))    last = test[at]    for i=2 to length(at) do        ai = at[i]        this = test[ai]        valid[ai] = last!=this        last = this    end for     nxt = find(0,valid)    if nxt then        for i=nxt+1 to length(test) do            if valid[i] then                test[nxt] = test[i]                nxt += 1            end if        end for        test = test[1..nxt-1]    end if    return testend function ?join(unique(split("Now is the time for all good men to come to the aid of the party.")))?unique({1, 2, 1, 4, 5, 2, 15, 1, 3, 4})?unique({1, 2, 3, "a", "b", "c", 2, 3, 4, "b", "c", "d"})?unique({1,3,2,9,1,2,3,8,8,1,0,2})?unique("chthonic eleemosynary paronomasiac")`
Output:
```"Now is the time for all good men to come aid of party."
{1,2,4,5,15,3}
{1,2,3,"a","b","c",4,"d"}
{1,3,2,9,8,0}
"chtoni elmsyarp"
```

## Phixmonti

`"Now" "is" "the" "time" "for" "all" "good" "men" "to" "come" "to" "the" "aid" "of" "the" "party." stklen tolist 0 tolist var newlist len for    get newlist over find    not if        swap 0 put var newlist    else        drop drop    endifendfor newlist print drop`

## PHP

`\$list = array(1, 2, 3, 'a', 'b', 'c', 2, 3, 4, 'b', 'c', 'd');\$unique_list = array_unique(\$list);`

## PicoLisp

There is a built-in function

`(uniq (2 4 6 1 2 3 4 5 6 1 3 5))`
Output:
`-> (2 4 6 1 3 5)`

## PL/I

`*process mar(1,72);remdup: Proc options(main);   declare t(20) fixed initial (6, 6, 1, 5, 6, 2, 1, 7,      5, 22, 4, 19, 1, 1, 6, 8, 9, 10, 11, 12);   declare (i, j, k, n, e) fixed;    put skip list ('Input:');   put edit ((t(k) do k = 1 to hbound(t))) (skip,20(f(3)));   n = hbound(t,1);   i = 0;outer:   do k = 1 to n;      e = t(k);      do j = k-1 to 1 by -1;          if e = t(j) then iterate outer;      end;      i = i + 1;      t(i) = e;   end;    put skip list ('Unique elements are:');   put edit ((t(k) do k = 1 to i)) (skip,20(f(3)));end;`
Output:
```Input:
6  6  1  5  6  2  1  7  5 22  4 19  1  1  6  8  9 10 11 12
Unique elements are:
6  1  5  2  7 22  4 19  8  9 10 11 12   ```

## Pop11

`;;; Initial arraylvars ar = {1 2 3 2 3 4};;;; Create a hash tablelvars ht= newmapping([], 50, 0, true);;;; Put all array as keys into the hash tablelvars i;for i from 1 to length(ar) do   1 -> ht(ar(i))endfor; ;;; Collect keys into a listlvars ls = [];appdata(ht, procedure(x); cons(front(x), ls) -> ls; endprocedure);`

## PostScript

Library: initlib
`  [10 8 8 98 32 2 4 5 10 ] dup length dict begin  aload let* currentdict {pop} map end `

## PowerShell

The common array for both approaches:

`\$data = 1,2,3,1,2,3,4,1`

Using a hash table to remove duplicates:

`\$h = @{}foreach (\$x in \$data) {    \$h[\$x] = 1}\$h.Keys`

Sorting and removing duplicates along the way can be done with the `Sort-Object` cmdlet.

`\$data | Sort-Object -Unique`

Removing duplicates without sorting can be done with the `Select-Object` cmdlet.

`\$data | Select-Object -Unique`

## Prolog

`uniq(Data,Uniques) :- sort(Data,Uniques).`

Example usage:

`?- uniq([1, 2, 3, 2, 3, 4],Xs).Xs = [1, 2, 3, 4]`

Because sort/2 is GNU prolog and not ISO here is an ISO compliant version:

`member1(X,[H|_]) :- X==H,!.member1(X,[_|T]) :- member1(X,T). distinct([],[]).distinct([H|T],C) :- member1(H,T),!, distinct(T,C).distinct([H|T],[H|C]) :- distinct(T,C).`

Example usage:

`?- distinct([A, A, 1, 2, 3, 2, 3, 4],Xs).Xs = [A, 1, 2, 3, 4]`

## PureBasic

Task solved with the built in Hash Table which are called Maps in PureBasic

`NewMap MyElements.s() For i=0 To 9              ;Mark 10 items at random, causing high risk of duplication items.  x=Random(9)  t\$="Number "+str(x)+" is marked"  MyElements(str(x))=t\$   ; Add element 'X' to the hash list or overwrite if already included.Next ForEach MyElements()  Debug MyElements()Next`

Output may look like this, e.g. duplicated items are automatically removed as they have the same hash value.

```Number 0 is marked
Number 2 is marked
Number 5 is marked
Number 6 is marked
```

## Python

If all the elements are hashable (this excludes list, dict, set, and other mutable types), we can use a set:

`items = [1, 2, 3, 'a', 'b', 'c', 2, 3, 4, 'b', 'c', 'd']unique = list(set(items))`

or if we want to keep the order of the elements

`items = [1, 2, 3, 'a', 'b', 'c', 2, 3, 4, 'b', 'c', 'd']unique = []helperset = set()for x in items:    if x not in helperset:        unique.append(x)        helperset.add(x)`

If all the elements are comparable (i.e. <, >=, etc. operators; this works for list, dict, etc. but not for complex and many other types, including most user-defined types), we can sort and group:

`import itertoolsitems = [1, 2, 3, 'a', 'b', 'c', 2, 3, 4, 'b', 'c', 'd']unique = [k for k,g in itertools.groupby(sorted(items))]`

If both of the above fails, we have to use the brute-force method, which is inefficient:

`items = [1, 2, 3, 'a', 'b', 'c', 2, 3, 4, 'b', 'c', 'd']unique = []for x in items:    if x not in unique:        unique.append(x)`

another way of removing duplicate elements from a list, while preserving the order would be to use OrderedDict module like so

` from collections import OrderedDict as od print(list(od.fromkeys([1, 2, 3, 'a', 'b', 'c', 2, 3, 4, 'b', 'c', 'd']).keys())) `

We may also need to specify the particular type (or degree) of uniqueness and duplication that is at issue. Case-insensitive, with strings ? Unique with respect to a particular key in the case of dictionaries ?

One way to do this is to require an equality predicate, or perhaps a key function, in addition to a list to be pruned. For example, using itertools.groupby, at the cost of needing a sort and discarding order:

`from itertools import (groupby)  # nubByKey :: (a -> b) -> [a] -> [a]def nubByKey(k, xs):    return list(list(v) for _, v in groupby(sorted(xs, key=k), key=k))  xs = [    'apple', 'apple',    'ampersand', 'aPPLE', 'Apple',    'orange', 'ORANGE', 'Orange', 'orange', 'apple']for k in [    id,                      # default case sensitive uniqueness    lambda x: x.lower(),     # case-insensitive uniqueness    lambda x: x,          # unique first character (case-sensitive)    lambda x: x.lower(),  # unique first character (case-insensitive)]:    print (        nubByKey(k, xs)    )`
Output:
```['apple', 'aPPLE', 'Apple', 'orange', 'ORANGE', 'Orange', 'ampersand']
['ampersand', 'apple', 'orange']
['Apple', 'ORANGE', 'apple', 'orange']
['apple', 'orange']```

Or alternatively, using an equality predicate with a recursive function which scales less well, but does preserve order:

`# nubByEq :: (a -> a -> Bool) -> [a] -> [a]def nubByEq(eq, xs):    def go(yys, xxs):        if yys:            y = yys            ys = yys[1:]            return go(ys, xxs) if (                elemBy(eq, y, xxs)            ) else (                [y] + go(ys, [y] + xxs)            )        else:            return []    return go(xs, [])  # elemBy :: (a -> a -> Bool) -> a -> [a] -> Booldef elemBy(eq, x, xs):    if xs:        return eq(x, xs) or elemBy(eq, x, xs[1:])    else:        return False  xs = [    'apple', 'apple',    'ampersand', 'aPPLE', 'Apple',    'orange', 'ORANGE', 'Orange', 'orange', 'apple']for eq in [    lambda a, b: a == b,                   # default case sensitive uniqueness    lambda a, b: a.lower() == b.lower(),   # case-insensitive uniqueness    lambda a, b: a == b,             # unique first char (case-sensitive)    lambda a, b: a.lower() == b.lower(),   # unique first char (any case)]:    print (        nubByEq(eq, xs)    )`

A briefer definition of which might be in terms of filter:

`# nubBy :: (a -> a -> Bool) -> [a] -> [a]def nubBy(p, xs):    def go(xs):        if xs:            x = xs            return [x] + go(                list(filter(                    lambda y: not p(x, y),                    xs[1:]                ))            )        else:            return []    return go(xs)`
Output:
```['apple', 'ampersand', 'aPPLE', 'Apple', 'orange', 'ORANGE', 'Orange']
['apple', 'ampersand', 'orange']
['apple', 'Apple', 'orange', 'ORANGE']
['apple', 'orange']```

## Qi

` (define remove-duplicates  []    -> []  [A|R] -> (remove-duplicates R) where (element? A R)  [A|R] -> [A|(remove-duplicates R)]) (remove-duplicates [a b a a b b c d e]) `

## R

`items <- c(1,2,3,2,4,3,2)unique (items)`

## Racket

Using the built-in function

` -> (remove-duplicates '(2 1 3 2.0 a 4 5 b 4 3 a 7 1 3 x 2))'(2 1 3 2.0 a 4 5 b 7 x) `

Using a hash-table:

` (define (unique/hash lst)  (hash-keys (for/hash ([x (in-list lst)]) (values x #t)))) `

Using a set:

` (define unique/set (compose1 set->list list->set)) `

A definition that works with arbitrary sequences and allows specification of an equality predicate.

` (define (unique seq #:same-test [same? equal?])  (for/fold ([res '()])            ([x seq] #:unless (memf (curry same? x) res))    (cons x res))) `
```-> (unique '(2 1 3 2.0 a 4 5 b 4 3 a 7 1 3 x 2))
'(1 2 3 a b x 4 5 7 2.0)
-> (unique '(2 1 3 2.0 4 5 4.0 3 7 1 3 2) #:same-test =)
'(7 5 4 3 1 2)
-> (unique #(2 1 3 2.0 4 5 4.0 3 7 1 3 2))
'(7 5 4 3 1 2)
-> (apply string (unique "absbabsbdbfbd"))
"fdsba"
```

## Raku

(formerly Perl 6)

`my @unique = [1, 2, 3, 5, 2, 4, 3, -3, 7, 5, 6].unique;`

Or just make a set of it.

`set(1,2,3,5,2,4,3,-3,7,5,6).list`

## Raven

`[ 1 2 3 'a' 'b' 'c' 2 3 4 'b' 'c' 'd' ] as itemsitems copy unique print list (8 items) 0 => 1 1 => 2 2 => 3 3 => "a" 4 => "b" 5 => "c" 6 => 4 7 => "d"`

## REBOL

`print mold unique [1 \$23.19 2 elbow 3 2 Bork 4 3 elbow 2 \$23.19]`
Output:
`[1 \$23.19 2 elbow 3 Bork 4]`

## Red

`>> items: [1 "a" "c" 1 3 4 5 "c" 3 4 5]>> unique items== [1 "a" "c" 3 4 5]`

## REXX

Note that in REXX, strings are quite literal.

•   +7   is different from     7   (but compares numerically equal).
•   00   is different from     0   (but compares numerically equal).
•   ─0   is different from     0   (but compares numerically equal).
•   7.     is different from     7   (but compares numerically equal).
•   Ab   is different from   AB   (but can compare equal if made case insensitive).

Note that all the REXX examples below don't care what   type   of element is used, integer, floating point, character, binary,   ···

### version 1, using method 1

`/*REXX program removes any duplicate elements (items) that are in a list (using a hash).*/\$= '2 3 5 7 11 13 17 19 cats 222 -100.2 +11 1.1 +7 7. 7 5 5 3 2 0 4.4 2'    /*item list.*/say 'original list:'     \$say right( words(\$), 17, '─')    'words in the original list.'z=;                              @.=             /*initialize the NEW list & index list.*/     do j=1  for words(\$);       y= word(\$, j)   /*process the words (items) in the list*/     if @.y==''  then z= z y;    @.y= .          /*Not duplicated? Add to Z list,@ array*/     end   /*j*/saysay 'modified list:'     space(z)                /*stick a fork in it,  we're all done. */say right( words(z), 17, '─')    'words in the modified list.'`
output   when using the default input list:
```original list: 2 3 5 7 11 13 17 19 cats 222 -100.2 +11 1.1 +7 7. 7 5 5 3 2 0 4.4
──────────────23  words in the original list.

modified list: 2 3 5 7 11 13 17 19 cats 222 -100.2 +11 1.1 +7 7. 0 4.4
──────────────17  words in the modified list.
```

### version 2, using a modified method 3

Instead of discard an element if it's a duplicated, it just doesn't add it to the new list.

Sorting of the list elements isn't necessary.

`/*REXX program removes any duplicate elements (items) that are in a list (using a list).*/\$= '2 3 5 7 11 13 17 19 cats 222 -100.2 +11 1.1 +7 7. 7 5 5 3 2 0 4.4 2'    /*item list.*/say 'original list:'     \$say right( words(\$), 17, '─')    'words in the original list.'#= words(\$)                                      /*process all the words in the list.   */     do j=#  by -1  for #;     y= word(\$, j)                       /*get right-to-Left. */     _= wordpos(y, \$, j + 1);  if _\==0  then \$= delword(\$, _, 1)  /*Dup? Then delete it*/     end   /*j*/saysay 'modified list:'     space(\$)                /*stick a fork in it,  we're all done. */say right( words(z), 17, '─')    'words in the modified list.'`
output   is identical to the 1st REXX version.

### version 3, using method 3

`/*REXX program removes any duplicate elements (items) that are in a list (using 2 lists)*/old = '2 3 5 7 11 13 17 19 cats 222 -100.2 +11 1.1 +7 7. 7 5 5 3 2 0 4.4 2'say 'original list:'   oldsay right( words(old), 17, '─')    'words in the original list.'new=                                             /*start with a clean  (list)  slate.   */     do j=1  for words(old);     _= word(old, j) /*process the words in the  OLD  list. */     if wordpos(_, new)==0  then new= new _      /*Doesn't exist?  Then add word to NEW.*/     end   /*j*/saysay 'modified list:'     space(new)              /*stick a fork in it,  we're all done. */say right( words(new), 17, '─')    'words in the modified list.'`
output   is identical to the 1st REXX version.

### version 4, using method 1 (hash table) via REXX stems

`/* REXX ************************************************************ * 26.11.2012 Walter Pachl * added: show multiple occurrences                                              **********************************************************************/ old='2 3 5 7 11 13 17 19 cats 222 -100.2 +11 1.1 +7 7. 7 5 5',              '3 2 0 4.4 2'                                                       say 'old list='old                                                      say 'words in the old list=' words(old)                                 new=''                                                                  found.=0                                                                count.=0                                                                Do While old<>''                                                          Parse Var old w old                                                     If found.w=0 Then Do                                                      new=new w                                                               found.w=1                                                               End                                                                   count.w=count.w+1                                                       End                                                                   say 'new list='strip(new)                                               say 'words in the new list=' words(new)                                 Say 'Multiple occurrences:'                                             Say 'occ word'                                                          Do While new<>''                                                          Parse Var new w new                                                     If count.w>1 Then                                                         Say right(count.w,3) w                                                End`
Output:
```old list=2 3 5 7 11 13 17 19 cats 222 -100.2 +11 1.1 +7 7. 7 5 5 3 2 0 4.4 2
words in the old list= 23
new list=2 3 5 7 11 13 17 19 cats 222 -100.2 +11 1.1 +7 7. 0 4.4
words in the new list= 17
Multiple occurrences:
occ word
3 2
2 3
3 5
2 7
```

## Ring

` list = ["Now", "is", "the", "time", "for", "all", "good", "men", "to", "come", "to", "the", "aid", "of", "the", "party."]for i = 1 to len(list)    for j = i + 1 to len(list)         if list[i] = list[j] del(list, j) j-- ok    nextnext for n = 1 to len(list)    see list[n] + " "nextsee nl `

Output:

```Now is the time for all good men to come aid of party.
```

## Ruby

Ruby has an `Array#uniq` built-in method, which returns a new array by removing duplicate values in self.

`ary = [1,1,2,1,'redundant',[1,2,3],[1,2,3],'redundant']p ary.uniq              # => [1, 2, "redundant", [1, 2, 3]]`

You can also write your own uniq method.

`class Array  # used Hash  def uniq1    each_with_object({}) {|elem, h| h[elem] = true}.keys  end  # sort (requires comparable)  def uniq2    sorted = sort    pre = sorted.first    sorted.each_with_object([pre]){|elem, uniq| uniq << (pre = elem) if elem != pre}  end  # go through the list  def uniq3    each_with_object([]) {|elem, uniq| uniq << elem unless uniq.include?(elem)}  endend ary = [1,1,2,1,'redundant',[1,2,3],[1,2,3],'redundant']p ary.uniq1             #=> [1, 2, "redundant", [1, 2, 3]]p ary.uniq2 rescue nil  #   Error (not comparable)p ary.uniq3             #=> [1, 2, "redundant", [1, 2, 3]] ary = [1,2,3,7,6,5,2,3,4,5,6,1,1,1]p ary.uniq1             #=> [1, 2, 3, 7, 6, 5, 4]p ary.uniq2             #=> [1, 2, 3, 4, 5, 6, 7]p ary.uniq3             #=> [1, 2, 3, 7, 6, 5, 4]`

A version without implementing class declarations:

`def unique(array)    pure = Array.new    for i in array        flag = false        for j in pure            flag = true if j==i        end        pure << i unless flag    end    return pureend unique ["hi","hey","hello","hi","hey","heyo"]   # => ["hi", "hey", "hello", "heyo"]unique [1,2,3,4,1,2,3,5,1,2,3,4,5]              # => [1,2,3,4,5]`

## Run BASIC

`a\$ = "2 3 5 7 11 13 17 19 cats 222 -100.2 +11 1.1 +7 7. 7 5 5 3 2 0 4.4 2" for i = 1 to len(a\$)  a1\$ = word\$(a\$,i)  if a1\$ = "" then exit for  for i1 = 1 to len(b\$)    if a1\$ = word\$(b\$,i1) then [nextWord]  next i1  b\$ = b\$ + a1\$ + " "[nextWord]next i  print "Dups:";a\$ print "No Dups:";b\$`
```Dups:2 3 5 7 11 13 17 19 cats 222 -100.2 +11 1.1 +7 7. 7 5 5 3 2 0 4.4 2
No Dups:2 3 5 7 11 13 17 19 cats 222 -100.2 +11 1.1 +7 7. 0 4.4 ```

## Rust

`use std::collections::HashSet;use std::hash::Hash; fn remove_duplicate_elements_hashing<T: Hash + Eq>(elements: &mut Vec<T>) {    let set: HashSet<_> = elements.drain(..).collect();    elements.extend(set.into_iter());} fn remove_duplicate_elements_sorting<T: Ord>(elements: &mut Vec<T>) {    elements.sort_unstable(); // order does not matter    elements.dedup();} fn main() {    let mut sample_elements = vec![0, 0, 1, 1, 2, 3, 2];    println!("Before removal of duplicates : {:?}", sample_elements);    remove_duplicate_elements_sorting(&mut sample_elements);    println!("After removal of duplicates : {:?}", sample_elements);}`
Output:
```Before removal of duplicates : [0, 0, 1, 1, 2, 3, 2]
After removal of duplicates : [1, 0, 3, 2]
```

## Scala

`val list = List(1,2,3,4,2,3,4,99)val l2 = list.distinct// l2: scala.List[scala.Int] = List(1,2,3,4,99) val arr = Array(1,2,3,4,2,3,4,99)val arr2 = arr.distinct// arr2: Array[Int] = Array(1, 2, 3, 4, 99) `

## Scheme

`(define (remove-duplicates l)  (cond ((null? l)         '())        ((member (car l) (cdr l))         (remove-duplicates (cdr l)))        (else         (cons (car l) (remove-duplicates (cdr l)))))) (remove-duplicates '(1 2 1 3 2 4 5))`
`(1 3 2 4 5)`

Alternative approach:

`(define (remove-duplicates l)  (do ((a '() (if (member (car l) a) a (cons (car l) a)))       (l l (cdr l)))    ((null? l) (reverse a)))) (remove-duplicates '(1 2 1 3 2 4 5))`
`(1 2 3 4 5)`

The function 'delete-duplicates' is also available in srfi-1.

## Seed7

`\$ include "seed7_05.s7i"; const proc: main is func  local    const array integer: data is [] (1, 3, 2, 9, 1, 2, 3, 8, 8, 1, 0, 2);    var set of integer: dataSet is (set of integer).value;    var integer: number is 0;  begin    for number range data do      incl(dataSet, number);    end for;    writeln(dataSet);  end func;`
Output:
```{0, 1, 2, 3, 8, 9}
```

## SETL

`items := [0,7,6,6,4,9,7,1,2,3,2];print(unique(items));`

Output in arbitrary order (convert tuple->set then set->tuple):

`proc unique(items);  return [item: item in {item: item in items}];end proc;`

Preserving source order

`proc unique(items);  seen := {};  return [item: item in items, nps in {#seen} | #(seen with:= item) > nps];end proc;`

`proc unique(items);  seen := {};  return [item: item in items, nps in {#seen} | #(seen with:= item) > nps];end proc;`
`items := [0,7,6,6,4,9,7,1,2,3,2];print(unique(items));`

Output in arbitrary order (convert tuple->set then set->tuple):

`proc unique(items);  return [item: item in {item: item in items}];end proc;`

## SETL4

` set = new('set')* Add all the elements of the array to the set.add(set,array) `

## Sidef

`var ary = [1,1,2,1,'redundant',[1,2,3],[1,2,3],'redundant'];say ary.uniq.dump;say ary.last_uniq.dump;`
Output:
```[1, 2, 'redundant', [1, 2, 3]]
[2, 1, [1, 2, 3], 'redundant']```

## Slate

`[|:s| #(1 2 3 4 1 2 3 4) >> s] writingAs: Set.  "==> {"Set traitsWindow" 1. 2. 3. 4}"`

## Smalltalk

`"Example of creating a collection"|a|a := #( 1 1 2 'hello' 'world' #symbol #another 2 'hello' #symbol ).a asSet.`
Output:
`Set (1 2 #symbol 'world' #another 'hello' )`

the above has the disadvantage of loosing the original order (because Sets are unordered, and the hashing shuffles elements into an arbitrary order). When tried, I got:

`Set('world' 1 #another 'hello' #symbol 2)`

on my system. This can be avoided by using an ordered set (which has also O(n) complexity) as below:

Works with: Smalltalk/X
`|a|a := #( 1 1 2 'hello' 'world' #symbol #another 2 'hello' #symbol ).a asOrderedSet.`
Output:
`OrderedSet(1 2 'hello' 'world' #symbol #another)`

## Sparkling

`function undupe(arr) {	var t = {};	foreach(arr, function(key, val) {		t[val] = true;	}); 	var r = {};	foreach(t, function(key) {		r[sizeof r] = key;	}); 	return r;}`

## Stata

### Duplicates in a dataset

Stata can report duplicate lines, or remove them. See duplicates in Stata help.

`. clear all. input x y1 11 11 22 12 21 12 12 11 22 2end . duplicates drop x y, force. list      +-------+     | x   y |     |-------|  1. | 1   1 |  2. | 1   2 |  3. | 2   1 |  4. | 2   2 |     +-------+`

### Mata

The uniqrows function removes duplicate rows from a matrix.

`. mata: a=1,1\1,1\1,2\2,1\2,2\1,1\2,1\2,1\1,2\2,2 : a        1   2     +---------+   1 |  1   1  |   2 |  1   1  |   3 |  1   2  |   4 |  2   1  |   5 |  2   2  |   6 |  1   1  |   7 |  2   1  |   8 |  2   1  |   9 |  1   2  |  10 |  2   2  |     +---------+ : uniqrows(a)       1   2    +---------+  1 |  1   1  |  2 |  1   2  |  3 |  2   1  |  4 |  2   2  |    +---------+`

## Swift

Requires elements to be hashable:

Works with: Swift version 1.2+
`println(Array(Set([3,2,1,2,3,4])))`
Output:
`[2, 3, 1, 4]`

Another solution (preserves order of first occurrence). Also requires elements to be hashable:

Works with: Swift version 1.2+
`func uniq<T: Hashable>(lst: [T]) -> [T] {  var seen = Set<T>(minimumCapacity: lst.count)  return lst.filter { x in    let unseen = !seen.contains(x)    seen.insert(x)    return unseen  }} println(uniq([3,2,1,2,3,4]))`
Output:
`[3, 2, 1, 4]`

Only requires elements to be equatable, but runs in O(n^2):

`func uniq<T: Equatable>(lst: [T]) -> [T] {  var seen = [T]()  return lst.filter { x in    let unseen = find(seen, x) == nil    if (unseen) {      seen.append(x)    }    return unseen  }} println(uniq([3,2,1,2,3,4]))`
Output:
`[3, 2, 1, 4]`

## Tcl

The concept of an "array" in Tcl is strictly associative - and since there cannot be duplicate keys, there cannot be a redundant element in an array. What is called "array" in many other languages is probably better represented by the "list" in Tcl (as in LISP). With the correct option, the `lsort` command will remove duplicates.

`set result [lsort -unique \$listname]`

## TUSCRIPT

` \$\$ MODE TUSCRIPTlist_old="b'A'A'5'1'2'3'2'3'4"list_sort=MIXED_SORT (list_old)list_new=REDUCE (list_sort)PRINT list_oldPRINT list_new `
Output:
(sorted)
```b'A'A'5'1'2'3'2'3'4
1'2'3'4'5'A'b
```

or

` \$\$ MODE TUSCRIPTlist_old="b'A'A'5'1'2'3'2'3'4"DICT list CREATELOOP l=list_oldDICT list LOOKUP l,numIF (num==0) DICT list ADD lENDLOOPDICT list unload listlist_new=JOIN (list)PRINT list_oldPRINT list_new `
Output:
```b'A'A'5'1'2'3'2'3'4
b'A'5'1'2'3'4
```

## UnixPipes

Assuming a sequence is represented by lines in a file.

`bash\$ # original listbash\$ printf '6\n2\n3\n6\n4\n2\n'623642bash\$ # made uniqbash\$ printf '6\n2\n3\n6\n4\n2\n'|sort -n|uniq2346bash\$`

or

`bash\$ # made uniqbash\$ printf '6\n2\n3\n6\n4\n2\n'|sort -nu2346bash\$`

## Ursala

The algorithm is to partition the list by equality and take one representative from each class, which can be done by letting the built in partition operator, |=, use its default comparison relation. This works on lists of any type including character strings but the comparison is based only on structural equivalence. It's up to the programmer to decide whether that's a relevant criterion for equivalence or else specify a better one.

`#cast %s example = |=hS& 'mississippi'`
Output:
`'mspi'`

## VBA

Hash Table Approach Input list (variant : Long, Double, Boolean and Strings) : Array(1.23456789101112E+16, True, False, True, "Alpha", 1, 235, 4, 1.25, 1.25, "Beta", 1.23456789101112E+16, "Delta", "Alpha", "Charlie", 1, 2, "Foxtrot", "Foxtrot", "Alpha", 235)

` Option Explicit Sub Main()Dim myArr() As Variant, i As Long     myArr = Remove_Duplicate(Array(1.23456789101112E+16, True, False, True, "Alpha", 1, 235, 4, 1.25, 1.25, "Beta", 1.23456789101112E+16, "Delta", "Alpha", "Charlie", 1, 2, "Foxtrot", "Foxtrot", "Alpha", 235))'return :     For i = LBound(myArr) To UBound(myArr)        Debug.Print myArr(i)    NextEnd Sub Private Function Remove_Duplicate(Arr As Variant) As Variant()Dim myColl As New Collection, Temp() As Variant, i As Long, cpt As Long     ReDim Temp(UBound(Arr))    For i = LBound(Arr) To UBound(Arr)        On Error Resume Next        myColl.Add CStr(Arr(i)), CStr(Arr(i))        If Err.Number > 0 Then            On Error GoTo 0        Else            Temp(cpt) = Arr(i)            cpt = cpt + 1        End If    Next i    ReDim Preserve Temp(cpt - 1)    Remove_Duplicate = TempEnd Function`
Output:
``` 1.23456789101112E+16
True
False
Alpha
1
235
4
1.25
Beta
Delta
Charlie
2
Foxtrot```

## VBScript

Hash Table Approach

` Function remove_duplicates(list)	arr = Split(list,",")	Set dict = CreateObject("Scripting.Dictionary")	For i = 0 To UBound(arr)		If dict.Exists(arr(i)) = False Then			dict.Add arr(i),""		End If	Next	For Each key In dict.Keys		tmp = tmp & key & ","	Next	remove_duplicates = Left(tmp,Len(tmp)-1)End Function WScript.Echo remove_duplicates("a,a,b,b,c,d,e,d,f,f,f,g,h") `
Output:
`a,b,c,d,e,f,g,h`

## Vedit macro language

The input "array" is an edit buffer where each line is one element.

`Sort(0, File_Size)                                          // sort the dataWhile(Replace("^(.*)\N\1\$", "\1", REGEXP+BEGIN+NOERR)){}    // remove duplicates`

## Vim Script

`call filter(list, 'count(list, v:val) == 1')`

## Visual FoxPro

` LOCAL i As Integer, n As Integer, lcOut As StringCLOSE DATABASES ALLCLEARCREATE CURSOR nums (num I)INDEX ON num TAG num COLLATE "Machine"SET ORDER TO 0n = 50RAND(-1)FOR i = 1 TO n    INSERT INTO nums VALUES (RanInt(1, 10))ENDFORSELECT num, COUNT(num) As cnt FROM nums ;GROUP BY num INTO CURSOR groupedLIST OFF TO FILE grouped.txt NOCONSOLElcOut = ""SCAN    lcOut = lcOut + TRANSFORM(num) + ","ENDSCANlcOut = LEFT(lcOut, LEN(lcOut)-1)? lcOut	 FUNCTION RanInt(tnLow As Integer, tnHigh As Integer) As IntegerRETURN INT((tnHigh - tnLow + 1)*RAND() + tnLow)ENDFUNC `
Output:
```NUM          COUNT
1              6
2              5
3              6
4              8
5              4
6              3
7              8
8              7
9              3

Unique Values: 1,2,3,4,5,6,7,8,9
```

## Wart

`def (dedup l)  let exists (table)    collect+each x l      unless exists.x        yield x      exists.x <- 1`
Output:
```dedup '(1 3 2 9 1 2 3 8 8 1 0 2)
=> (1 3 2 9 8 0)```

## Wortel

`@uniq [1 2 3 2 1 2 3] ; returns [1 2 3]`

## XPL0

`code Text=12;           \built-in routine to display a string of charactersstring 0;               \use zero-terminated strings (not MSb terminated) func StrLen(S);         \Return number of characters in an ASCIIZ stringchar S;int  I;for I:= 0, -1>>1-1 do   \(limit = 2,147,483,646 if 32 bit, or 32766 if 16 bit)        if S(I) = 0 then return I; func Unique(S);         \Remove duplicate bytes from stringchar S;int  I, J, K, L;[L:= StrLen(S);                         \string lengthfor I:= 0 to L-1 do                     \for all characters in string...    for J:= I+1 to L-1 do               \scan rest of string for duplicates        if S(I) = S(J) then             \if duplicate then            [for K:= J+1 to L do        \ shift rest of string down (including                S(K-1):= S(K);          \ terminating zero)            L:= L-1                     \ string is now one character shorter            ];return S;                               \return pointer to string]; Text(0, Unique("Pack my box with five dozen liquor jugs."))`
Output:
```Pack myboxwithfvedznlqurjgs.
```

## Yabasic

`data "Now", "is", "the", "time", "for", "all", "good", "men", "to", "come", "to", "the", "aid", "of", "the", "party.", "" do    read p\$    if p\$ = "" break    if not instr(r\$, p\$) r\$ = r\$ + p\$ + " "loop print r\$`

## zkl

Using built ins:

`zkl: Utils.Helpers.listUnique(T(1,3,2,9,1,2,3,8,8,"8",1,0,2,"8"))L(1,3,2,9,8,"8",0)zkl: "1,3,2,9,1,2,3,8,8,1,0,2".unique(),012389`

Where listUnique is brute force:

`fcn listUnique(xs){   xs.reduce(fcn(us,s){us.holds(s) and us or us.append(s)},L()) }`

## Zoea

` program: remove_duplicate_elements  input: [1,2,1,3,2,4,1]  output: [1,2,3,4] `