Repeat a string
From Rosetta Code
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) => "*****").
[edit] 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.
[edit] Iterative version
function repeatString(string:String, numTimes:uint):String
{
var output:String = "";
for(var i:uint = 0; i < numTimes; i++)
output += string;
return output;
}
[edit] Recursive version
The following double-and-add method is much faster when repeating a string many times.
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;
}
[edit] Ada
In Ada multiplication of an universal integer to string gives the desired result. Here is an example of use:
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;
Sample output:
hahahahaha
[edit] ALGOL 68
print (5 * "ha")
[edit] 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 = (char *)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;
}
A variation.
...
char *string_repeat(char *str, int n)
{
char *pa, *pb;
size_t slen = strlen(str);
char *dest = (char *)malloc(n*slen+1);
pa = dest + (n-1)*slen;
strcpy(pa, str);
pb = --pa + slen;
while (pa>=dest) *pa-- = *pb--;
return dest;
}
To repeat a single character
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char * char_repeat( int n, char c ) {
char * dest = (char *)calloc(n+1, sizeof(char));
memset(dest, c, n);
return dest;
}
int main() {
printf("%s\n", char_repeat(5, '*'));
return 0;
}
[edit] C++
#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 ;
}
To repeat a single character:
#include <string>
#include <iostream>
int main( ) {
std::cout << std::string( 5, '*' ) << std::endl ;
return 0 ;
}
[edit] C#
String s = "".PadLeft(5, 'X').Replace("X", "ha")
To repeat a single character:
String s = "".PadLeft(5, '*')
[edit] Clojure
(apply str (repeat 5 "ha"))
[edit] Common Lisp
(defun repeat-string (n string)
(with-output-to-string (stream)
(loop repeat n do (write-string string stream))))
(princ (repeat-string 5 "hi"))
A single character may be repeated using just the builtin make-string:
(make-string 5 :initial-element #\X)
produces “XXXXX”.
[edit] D
Repeating a string:
import std.stdio;
import std.string;
void main()
{
writefln(repeat("ha", 5));
}
Repeating a character with vector operations:
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);
}
[edit] E
"ha" * 5
[edit] Factor
: repeat-string ( str n -- str' ) swap <repetition> concat ;
"ha" 5 repeat-string print
[edit] 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
The same code without the use of locals:
( 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
Filling a string with a single character is supported by ANS-Forth:
create test 256 allot
test 10 char * fill \ repeat a single character
test 10 type
[edit] Fortran
Works with: Fortran version 90 and later
program test_repeat
write (*, '(a)') repeat ('ha', 5)
end program test_repeat
Output:
hahahahaha
[edit] Haskell
For a string of finite length:
concat $ replicate 5 "ha"
For an infinitely long string:
cycle "ha"
To repeat a single character:
replicate 5 '*'
[edit] 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
[edit] 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.
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));
}
Or even shorter:
public static String repeat(String str, int times){
return new String(new char[times]).replace("\0", str);
}
[edit] JavaScript
This solution creates an array of n+1 null elements, then joins them using the target string as the delimiter
String.prototype.repeat = function(n) {
return new Array(1 + parseInt(n, 10)).join(this);
}
alert("ha".repeat(5)); // hahahahaha
[edit] Logo
to copies :n :thing [:acc "||]
if :n = 0 [output :acc]
output (copies :n-1 :thing combine :acc :thing)
end
or using cascade:
show cascade 5 [combine "ha ?] "|| ; hahahahaha
[edit] Lua
function repeats(s, n) return n > 0 and s .. repeat(s, n-1) or "" end
[edit] 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)
;;
testing in the toplevel:
# string_repeat "Hiuoa" 3 ;;
- : string = "HiuoaHiuoaHiuoa"
Alternately:
let string_repeat s n =
String.concat "" (Array.to_list (Array.make n s))
;;
Or:
let string_repeat s n =
Array.fold_left (^) "" (Array.make n s)
;;
To repeat a single character:
String.make 5 '*'
[edit] Oz
We have to write a function for this:
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}}
[edit] Perl
"ha" x 5
[edit] Perl 6
Works with: Rakudo version #21 "Seattle"
"ha" x 5
(Note that the x operator isn't quite the same as in Perl 5: it now only creates strings. To create lists, use xx.)
[edit] PHP
str_repeat("ha", 5)
[edit] PicoLisp
(pack (need 5 NIL "ha"))
-> "hahahahaha"
or:
(pack (make (do 5 (link "ha"))))
-> "hahahahaha"
[edit] PL/I
s = copy('ha', 5);
/* To repeat a single character a fixed number of times: */
s = (5)(1)'h';
[edit] 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
[edit] PowerBASIC
MSGBOX REPEAT$(5, "ha")
[edit] Pure
str_repeat is defined by pattern-matching: repeating any string 0 times results in the empty string; while repeating it more than 0 times results in the concatenation of the string and (n-1) further repeats.
> str_repeat 0 s = "";
> str_repeat n s = s + (str_repeat (n-1) s) if n>0;
> str_repeat 5 "ha";
"hahahahaha"
>
[edit] PureBasic
Procedure.s RepeatString(count, text$=" ")
Protected i, ret$=""
For i = 1 To count
ret$ + text$
Next
ProcedureReturn ret$
EndProcedure
Debug RepeatString(5, "ha")
[edit] Python
"ha" * 5 # ==> "hahahahaha"
"Characters" are just strings of length one.
[edit] PowerShell
"ha" * 5 # ==> "hahahahaha"
[edit] R
paste(rep("ha",5), collapse='')
[edit] Ruby
"ha" * 5 # ==> "hahahahaha"
[edit] Scala
"ha" * 5 // ==> "hahahahaha"
[edit] Scheme
Works with: ?
(define (string-repeat n str)
(fold string-append "" (make-list n str)))
(string-repeat 5 "ha") ==> "hahahahaha"
To repeat a single character:
(string-make 5 #\*)
[edit] SNOBOL4
output = dupl("ha",5)
end
[edit] Suneido
'ha'.Repeat(5) --> "hahahahaha"
'*'.Repeat(5) --> "*****"
[edit] Tcl
string repeat "ha" 5 ;# => hahahahaha
[edit] Ursala
#import nat
repeat = ^|DlSL/~& iota
#cast %s
example = repeat('ha',5)
output:
'hahahahaha'
