Repeat a string: Difference between revisions

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Take a string and repeat it some number of times. Example: repeat("ha", 5) => "hahahahaha"

If there is a simpler/more efficient way to repeat a single “character” (i.e. creating a string filled with a certain character), you might want to show that as well (i.e. repeat-char("*", 5) => "*****").

4DOS Batch

<lang 4dos>gosub repeat ha 5 echo %@repeat[*,5] quit

Repeat [String Times]

   do %Times%
       echos %String%
   enddo
   echo.

return</lang> Output shows:

hahahahaha
*****

ActionScript

ActionScript does not have a built-in way to repeat a string multiple times, but the addition operator can be used to concatenate strings.

Iterative version

<lang ActionScript>function repeatString(string:String, numTimes:uint):String { var output:String = ""; for(var i:uint = 0; i < numTimes; i++) output += string; return output; }</lang>

Recursive version

The following double-and-add method is much faster when repeating a string many times. <lang ActionScript>function repeatRecursive(string:String, numTimes:uint):String { if(numTimes == 0) return ""; if(numTimes & 1) return string + repeatRecursive(string, numTimes - 1); var tmp:String = repeatRecursive(string, numTimes/2); return tmp + tmp; }</lang>

Ada

In Ada multiplication of an universal integer to string gives the desired result. Here is an example of use: <lang Ada>with Ada.Strings.Fixed; use Ada.Strings.Fixed; with Ada.Text_IO; use Ada.Text_IO;

procedure String_Multiplication is begin

  Put_Line (5 * "ha");

end String_Multiplication;</lang> Sample output:

hahahahaha

ALGOL 68

<lang algol68>print (5 * "ha") </lang>

AutoHotkey

<lang AutoHotkey>MsgBox % Repeat("ha",5)

Repeat(String,Times) {

 Loop, %Times%
   Output .= String
 Return Output

}</lang>

Bash

<lang bash>printf "ha%.0s" {1..5}</lang> A slightly more generic version <lang bash>repeat() {

 eval "printf '${1}%.0s' {1..${2}}"

}</lang>

Batch File

Commandline implementation

<lang dos>@echo off if "%2" equ "" goto fail setlocal enabledelayedexpansion set char=%1 set num=%2 for /l %%i in (1,1,%num%) do set res=!res!%char% echo %res%

fail</lang>

'Function' version

<lang dos>@echo off setlocal enabledelayedexpansion if "%2" equ "" goto fail call :repeat %1 %2 res echo %res% goto :eof

repeat

set char=%1 set num=%2 for /l %%i in (1,1,%num%) do set %3=!%3!%char% goto :eof

fail</lang>

Brainf***

<lang bf>+++++ +++++ init first as 10 counter [-> +++++ +++++<] we add 10 to second each loopround

Now we want to loop 5 times to follow std +++++ [-> ++++ . ----- -- . +++<] print h and a each loop

and a newline because I'm kind and it looks good +++++ +++++ +++ . --- .</lang>

C

<lang c>#include <stdio.h>

include <stdlib.h>
include <string.h>

char * string_repeat( int n, const char * s ) {

 size_t slen = strlen(s);
 char * dest = calloc(n*slen+1, sizeof(char));

 int i; char * p;
 for ( i=0, p = dest; i < n; ++i, p += slen ) {
   memcpy(p, s, slen);
 }
 return dest;

}

int main() {

 printf("%s\n", string_repeat(5, "ha"));
 return 0;

}</lang> A variation. <lang c>... char *string_repeat(char *str, int n) {

  char *pa, *pb;
  size_t slen = strlen(str);
  char *dest = malloc(n*slen+1);

  pa = dest + (n-1)*slen;
  strcpy(pa, str);
  pb = --pa + slen; 
  while (pa>=dest) *pa-- = *pb--;
  return dest;

}</lang>

To repeat a single character <lang c>#include <stdio.h>

include <stdlib.h>
include <string.h>

char * char_repeat( int n, char c ) {

 char * dest = calloc(n+1, sizeof(char));
 memset(dest, c, n);
 return dest;

}

int main() {

 printf("%s\n", char_repeat(5, '*'));
 return 0;

}</lang>

C++

<lang cpp>#include <string>

include <iostream>

std::string repeat( const std::string &word, int times ) {

  std::string result ;
  result.reserve(times*word.length()); // avoid repeated reallocation
  for ( int a = 0 ; a < times ; a++ ) 
     result += word ;
  return result ;

}

int main( ) {

  std::cout << repeat( "Ha" , 5 ) << std::endl ;
  return 0 ;

}</lang>

To repeat a single character: <lang cpp>#include <string>

include <iostream>

int main( ) {

  std::cout << std::string( 5, '*' ) << std::endl ;
  return 0 ;

}</lang>

C#

<lang csharp>String s = "".PadLeft(5, 'X').Replace("X", "ha")</lang>

To repeat a single character: <lang csharp>String s = "".PadLeft(5, '*')</lang>

Or for a single character use the String(char, int) constructor: <lang csharp>String s = new String('*', 5);</lang>

Clojure

<lang lisp>(apply str (repeat 5 "ha"))</lang>

Common Lisp

<lang lisp>(defun repeat-string (n string)

 (with-output-to-string (stream)
   (loop repeat n do (write-string string stream))))

(princ (repeat-string 5 "hi"))</lang>

A single character may be repeated using just the builtin make-string: <lang lisp>(make-string 5 :initial-element #\X)</lang> produces “XXXXX”.

D

Repeating a string: <lang d>import std.stdio; import std.string;

void main() {

   writefln(repeat("ha", 5));

}</lang> Repeating a character with vector operations: <lang d>import std.stdio;

void main() {

   char[]str; // create the dynamic array
   str.length = 5; // set the length
   str[]='*'; // set all characters in the string to '*'
   writefln(str);

}</lang>

E

Erlang

This example uses list comprehensions to accumulate N copies of X: <lang erlang> repeat(X,N) ->

   lists:flatten([ X || _ <- lists:seq(1,N)]).

</lang> This example uses lists:flatmap to do the same: <lang erlang> repeat(X,N) ->

   lists:flatmap(fun (_) -> X end, lists:seq(1,N)).

</lang>

The first version also works for characters or any other values (though deeplists will all be flattened). The second version requires that X be a list, anything else will result in a bad argument exception.

Factor

<lang factor>: repeat-string ( str n -- str' ) swap <repetition> concat ;

"ha" 5 repeat-string print</lang>

Forth

<lang forth>: place-n { src len dest n -- }

 0 dest c!
 n 0 ?do src len dest +place loop ;

create test 256 allot s" ha" test 5 place-n test count type \ hahahahaha</lang> The same code without the use of locals: <lang forth> ( src len dest n -- )

place-n 0 over c! 0 ?do >r 2dup r@ +place r> loop drop 2drop ;

create test 256 allot s" ha" test 5 place-n test count type cr \ hahahahaha</lang> Filling a string with a single character is supported by ANS-Forth: <lang forth>create test 256 allot

test 10 char * fill \ repeat a single character test 10 type</lang>

Fortran

Works with: Fortran version 90 and later

<lang fortran>program test_repeat

 write (*, '(a)') repeat ('ha', 5)

end program test_repeat</lang> Output:

hahahahaha

F#

<lang fsharp>> String.Concat( Array.create 5 "ha" );; val it : string = "hahahahaha"</lang>

Go

<lang go>fmt.Println(strings.Repeat("ha", 5)) # ==> "hahahahaha"</lang> "Characters" are just strings of length one.

Groovy

<lang groovy> println 'ha' * 5</lang>

Haskell

For a string of finite length:

<lang haskell>concat $ replicate 5 "ha"</lang>

For an infinitely long string:

<lang haskell>cycle "ha"</lang>

To repeat a single character:

<lang haskell>replicate 5 '*'</lang>

HicEst

<lang HicEst>CHARACTER out*20

EDIT(Text=out, Insert="ha", DO=5)</lang>

Icon and Unicon

Icon

The procedure repl is a supplied function in Icon and Unicon. <lang Icon>procedure main(args)

   write(repl(integer(!args) | 5))

end</lang> If it weren't, one way to write it is: <lang Icon>procedure repl(s, n)

   every (ns := "") ||:= |s\(0 <= n)
   return ns

end</lang>

Unicon

This Icon solution works in Unicon.

Inform 7

<lang inform7>Home is a room.

To decide which indexed text is (T - indexed text) repeated (N - number) times: let temp be indexed text; repeat with M running from 1 to N: let temp be "[temp][T]"; decide on temp.

When play begins: say "ha" repeated 5 times; end the story.</lang>

J

<lang j> 5 # '*' NB. repeat each item 5 times

  5 # 'ha'              NB. repeat each item 5 times

hhhhhaaaaa

  (5 * # 'ha') $ 'ha'   NB. repeat array 5 times (explicit)

hahahahaha

  5 ((* #) $ ]) 'ha'    NB. repeat array 5 times (tacit)

hahahahaha</lang>

Java

Works with: Java version 1.5+

There's no function or operator to do this in Java, so you have to do it yourself. <lang java5>public static String repeat(String str, int times){

  StringBuilder ret = new StringBuilder();
  for(int i = 0;i < times;i++) ret.append(str);
  return ret.toString();

}

public static void main(String[] args){

 System.out.println(repeat("ha", 5));

}</lang>

Or even shorter: <lang java5>public static String repeat(String str, int times){

  return new String(new char[times]).replace("\0", str);

}</lang>

JavaScript

This solution creates an array of n+1 null elements, then joins them using the target string as the delimiter <lang javascript>String.prototype.repeat = function(n) {

   return new Array(1 + parseInt(n, 10)).join(this);

}

alert("ha".repeat(5)); // hahahahaha</lang>

Liberty BASIC

<lang lb>a$ ="ha " print StringRepeat$( a$, 5)

end

function StringRepeat$( in$, n)

   o$ =""
   for i =1 to n
       o$ =o$ +in$
   next i
   StringRepeat$ =o$

end function</lang>

Logo

<lang logo>to copies :n :thing [:acc "||]

 if :n = 0 [output :acc]
 output (copies :n-1 :thing combine :acc :thing)

end</lang> or using cascade: <lang logo>show cascade 5 [combine "ha ?] "|| ; hahahahaha</lang>

Lua

<lang lua>function repeats(s, n) return n > 0 and s .. repeat(s, n-1) or "" end

Or use native string library function string.rep(s,n)

</lang>

MUMPS

<lang MUMPS> RPTSTR(S,N)

;Repeat a string S for N times
NEW I
FOR I=1:1:N WRITE S
KILL I
QUIT

RPTSTR1(S,N) ;Functionally equivalent, but denser to read

F I=1:1:N W S
Q

</lang>

Objeck

<lang objeck> bundle Default {

 class Repeat {
   function : Main(args : String[]) ~ Nil {
     Repeat("ha", 5)->PrintLine();
   }
   
   function : Repeat(string : String, max : Int) ~ String {
     repeat : String := String->New();
     for(i := 0; i < max; i += 1;) {
       repeat->Append(string);
     };
     
     return repeat;
   }
 }

} </lang>

OCaml

<lang ocaml>let string_repeat s n =

 let len = String.length s in
 let res = String.create(n * len) in
 for i = 0 to pred n do
   String.blit s 0 res (i * len) len;
 done;
 (res)

</lang>

testing in the toplevel: <lang ocaml># string_repeat "Hiuoa" 3 ;; - : string = "HiuoaHiuoaHiuoa"</lang>

Alternately: <lang ocaml>let string_repeat s n =

 String.concat "" (Array.to_list (Array.make n s))

</lang>

Or: <lang ocaml>let string_repeat s n =

 Array.fold_left (^) "" (Array.make n s)

</lang>

To repeat a single character: <lang ocaml>String.make 5 '*'</lang>

Oz

We have to write a function for this: <lang oz>declare

 fun {Repeat Xs N}
    if N > 0 then
       {Append Xs {Repeat Xs N-1}}
    else
       nil
    end
 end

in

 {System.showInfo {Repeat "Ha" 5}}</lang>

Perl

Perl 6

Works with: Rakudo version #21 "Seattle"

(Note that the x operator isn't quite the same as in Perl 5: it now only creates strings. To create lists, use xx.)

PHP

<lang php>str_repeat("ha", 5)</lang>

PicoLisp

<lang PicoLisp>(pack (need 5 "ha")) -> "hahahahaha"</lang> or: <lang PicoLisp>(pack (make (do 5 (link "ha")))) -> "hahahahaha"</lang>

PL/I

<lang PL/I> s = copy('ha', 5);

/* To repeat a single character a fixed number of times: */

s = (5)(1)'h'; </lang>

PostScript

<lang PostScript>% the comments show the stack content after the line was executed % where rcount is the repeat count, "o" is for orignal, % "f" is for final, and iter is the for loop variable % % usage: rcount ostring times -> fstring

/times {

 dup length dup    % rcount ostring olength olength
 4 3 roll          % ostring olength olength rcount
 mul dup string    % ostring olength flength fstring
 4 1 roll          % fstring ostring olength flength
 1 sub 0 3 1 roll  % fstring ostring 0 olength flength_minus_one 
 {                 % fstring ostring iter
   1 index 3 index % fstring ostring iter ostring fstring
   3 1 roll        % fstring ostring fstring iter ostring
   putinterval     % fstring ostring
 } for
 pop               % fstring

} def</lang>

PowerBASIC

<lang powerbasic>MSGBOX REPEAT$(5, "ha")</lang>

PowerShell

<lang powershell>"ha" * 5 # ==> "hahahahaha"</lang>

Prolog

<lang prolog> %repeat(Str,Num,Res). repeat(Str,1,Str). repeat(Str,Num,Res):-

   Num1 is Num-1,
   repeat(Str,Num1,Res1),
   string_concat(Str, Res1, Res).

</lang>

Pure

str_repeat is defined by pattern-matching: repeating any string 0 times results in the empty string; while repeating it more than 0 times results in the concatenation of the string and (n-1) further repeats.

<lang pure>> str_repeat 0 s = ""; > str_repeat n s = s + (str_repeat (n-1) s) if n>0; > str_repeat 5 "ha"; "hahahahaha" ></lang>

PureBasic

<lang PureBasic>Procedure.s RepeatString(count, text$=" ")

  Protected i, ret$=""

  For i = 1 To count
     ret$ + text$
  Next
  ProcedureReturn ret$

EndProcedure

Debug RepeatString(5, "ha")</lang>

Python

<lang python>"ha" * 5 # ==> "hahahahaha"</lang> "Characters" are just strings of length one.

R

<lang ruby>paste(rep("ha",5), collapse=)</lang>

REBOL

<lang rebol>head insert/dup "" "ha" 5</lang>

Retro

<lang Retro>with strings'

repeatString ( $n-$ )

 1- [ dup ] dip [ over prepend ] times nip ;

"ha" 5 repeatString</lang>

REXX

              /*all examples are equivalent, but not created equal.*/

/*---------------------*/

y='ha' z=copies(y,5)

/*---------------------*/

y='ha' z = copies( 'ha', 5 )

/*---------------------*/

y='ha' z=y||y||y||y||y

/*---------------------*/

y= 'ha' z= y || y || y || y || y

/*---------------------*/

y='ha' z=

 do 5
 z=z || y
 end

/*---------------------*/

y="ha" z=

 do 5
 z=z||y
 end

/*---------------------*/ </lang>

Ruby

<lang ruby>"ha" * 5 # ==> "hahahahaha"</lang>

Scala

<lang scala>"ha" * 5 // ==> "hahahahaha"</lang>

Scheme

Works with: ?

<lang scheme>(define (string-repeat n str) (fold string-append "" (make-list n str))) (string-repeat 5 "ha") ==> "hahahahaha"</lang>

To repeat a single character: <lang scheme>(make-string 5 #\*)</lang>

SNOBOL4

<lang snobol4> output = dupl("ha",5) end </lang>

SQL

<lang sql>select rpad(, 10, 'ha')</lang>

Standard ML

<lang sml>fun string_repeat (s, n) =

 concat (List.tabulate (n, fn _ => s))

</lang>

testing in the interpreter: <lang sml>- string_repeat ("Hiuoa", 3) ; val it = "HiuoaHiuoaHiuoa" : string</lang>

To repeat a single character: <lang sml>fun char_repeat (c, n) =

 implode (List.tabulate (n, fn _ => c))

</lang>

cast %s

example = repeat('ha',5)</lang> output:

'hahahahaha'

Visual Basic .NET

There is a simple instruction do repeat a char or a string the specified number of times (must be greater than 0). <lang vbnet>String(5, "ha") String(5, "*"C)</lang> Those produces:

hahahahaha
*****

Yorick

<lang yorick>array("ha", 5)(sum)</lang>