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{{task|Basic language learning}} [[Category:String manipulation]] [[Category: String manipulation]] {{basic data operation}} [[Category:Simple]]
Most languages provide a way to concatenate two string values, but some languages also provide a convenient way to append in-place to an existing string variable without referring to the variable twice.
;Task: Create a string variable equal to any text value.
Append the string variable with another string literal in the most idiomatic way, without double reference if your language supports it.
Show the contents of the variable after the append operation.
Ada
with Ada.Strings.Unbounded; use Ada.Strings.Unbounded;
with Ada.Text_IO.Unbounded_Io; use Ada.Text_IO.Unbounded_IO;
procedure String_Append is
Str : Unbounded_String := To_Unbounded_String("Hello");
begin
Append(Str, ", world!");
Put_Line(Str);
end String_Append;
{{out}}
Hello, world!
ALGOL 68
{{works with|ALGOL 68|Revision 1.}} {{works with|ALGOL 68G|Any - tested with release [http://sourceforge.net/projects/algol68/files/algol68g/algol68g-2.7 algol68g-2.7].}} {{works with|ELLA ALGOL 68|Any (with appropriate job cards).}} '''File: String_append.a68'''
#!/usr/bin/a68g --script #
# -*- coding: utf-8 -*- #
STRING str := "12345678";
str +:= "9!";
print(str)
{{out}}
123456789!
ARM Assembly
{{works with|as|Raspberry Pi}}
/* ARM assembly Raspberry PI */
/* program appendstr.s */
/* Constantes */
.equ STDOUT, 1 @ Linux output console
.equ EXIT, 1 @ Linux syscall
.equ WRITE, 4 @ Linux syscall
.equ BUFFERSIZE, 100
/* Initialized data */
.data
szMessString: .asciz "String :\n"
szString1: .asciz "Alphabet : "
sComplement: .fill BUFFERSIZE,1,0
szString2: .asciz "abcdefghijklmnopqrstuvwxyz"
szCarriageReturn: .asciz "\n"
/* UnInitialized data */
.bss
/* code section */
.text
.global main
main:
ldr r0,iAdrszMessString @ display message
bl affichageMess
ldr r0,iAdrszString1 @ display begin string
bl affichageMess
ldr r0,iAdrszCarriageReturn @ display line return
bl affichageMess
ldr r0,iAdrszString1
ldr r1,iAdrszString2
bl append @ append sting2 to string1
ldr r0,iAdrszMessString
bl affichageMess
ldr r0,iAdrszString1 @ display string
bl affichageMess
ldr r0,iAdrszCarriageReturn
bl affichageMess
100: @ standard end of the program
mov r0, #0 @ return code
mov r7, #EXIT @ request to exit program
svc 0 @ perform system call
iAdrszMessString: .int szMessString
iAdrszString1: .int szString1
iAdrszString2: .int szString2
iAdrszCarriageReturn: .int szCarriageReturn
/******************************************************************/
/* append two strings */
/******************************************************************/
/* r0 contains the address of the string1 */
/* r1 contains the address of the string2 */
append:
push {r0,r1,r2,r7,lr} @ save registers
mov r2,#0 @ counter byte string 1
1:
ldrb r3,[r0,r2] @ load byte string 1
cmp r3,#0 @ zero final ?
addne r2,#1
bne 1b @ no -> loop
mov r4,#0 @ counter byte string 2
2:
ldrb r3,[r1,r4] @ load byte string 2
strb r3,[r0,r2] @ store byte string 1
cmp r3,#0 @ zero final ?
addne r2,#1 @ no -> increment counter 1
addne r4,#1 @ no -> increment counter 2
bne 2b @ no -> loop
100:
pop {r0,r1,r2,r7,lr} @ restaur registers
bx lr @ return
/******************************************************************/
/* display text with size calculation */
/******************************************************************/
/* r0 contains the address of the message */
affichageMess:
push {r0,r1,r2,r7,lr} @ save registers
mov r2,#0 @ counter length */
1: @ loop length calculation
ldrb r1,[r0,r2] @ read octet start position + index
cmp r1,#0 @ if 0 its over
addne r2,r2,#1 @ else add 1 in the length
bne 1b @ and loop
@ so here r2 contains the length of the message
mov r1,r0 @ address message in r1
mov r0,#STDOUT @ code to write to the standard output Linux
mov r7, #WRITE @ code call system "write"
svc #0 @ call system
pop {r0,r1,r2,r7,lr} @ restaur registers
bx lr @ return
AutoHotkey
s := "Hello, "
s .= "world."
MsgBox % s
{{out}}
Hello, world.
AWK
# syntax: GAWK -f STRING_APPEND.AWK
BEGIN {
s = "foo"
s = s "bar"
print(s)
exit(0)
}
{{out}}
foobar
Axe
Lbl STRCAT
Copy(r₂,r₁+length(r₁),length(r₂)+1)
r₁
Return
BASIC
=
Applesoft BASIC
=
S$ = "Hello"
S$ = S$ + " World!"
PRINT S$
=
BBC BASIC
=
S$="Hello"
S$+=" World!"
PRINT S$
END
{{out}}
Hello World!
==={{header|IS-BASIC}}===
## Bracmat
```Bracmat
str="Hello";
str$(!str " World!"):?str;
out$!str;
{{out}}
Hello World!
C
#include <stdio.h>
#include <string.h>
int main()
{
char str[24]="Good Morning";
char *cstr=" to all";
char *cstr2=" !!!";
int x=0;
//failure when space allocated to str is insufficient.
if(sizeof(str)>strlen(str)+strlen(cstr)+strlen(cstr2))
{
/* 1st method*/
strcat(str,cstr);
/*2nd method*/
x=strlen(str);
sprintf(&str[x],"%s",cstr2);
printf("%s\n",str);
}
return 0;
}
{{out}}
Good Morning to all !!!
C++
#include <iostream>
#include <string>
int main( ) {
std::string greeting( "Hello" ) ;
greeting.append( " , world!" ) ;
std::cout << greeting << std::endl ;
return 0 ;
}
{{out}}
Hello , world!
C#
class Program
{
static void Main(string[] args)
{
string x = "foo";
x += "bar";
System.Console.WriteLine(x);
}
}
Clojure
Using global vars.
(def s "app")
#'user/s
user=> s
"app"
user=> (def s (str s "end"))
#'user/s
user=> s
"append"
Using local bindings.
user=> (let [s "ap", s (str s "pend")] s)
"append"
COBOL
COBOL is not really a variable length field programming language. Most data items are fixed in size at compile time.
This example uses OCCURS DEPENDING ON, and ''reference modification'' to simulate a string append, all within an already maximally bounded character field. This type of programming task, while possible, is not overly common in COBOL applications.
{{works with|GnuCOBOL}}
identification division.
program-id. string-append.
data division.
working-storage section.
01 some-string.
05 elements pic x occurs 0 to 80 times depending on limiter.
01 limiter usage index value 7.
01 current usage index.
procedure division.
append-main.
move "Hello, " to some-string
*> extend the limit and move using reference modification
set current to length of some-string
set limiter up by 5
move "world" to some-string(current + 1:)
display some-string
goback.
end program string-append.
{{out}}
$ cobc -xj string-append.cob
Hello, world
=={{Header|CoffeeScript}}== {{works with|Node.js}}
a = "Hello, "
b = "World!"
c = a + b
console.log c
Or with concat:
console.log "Hello, ".concat "World!"
{{out}}
Hello, World!
Common Lisp
Similar to the [[String append#Racket| Racket]] solution, a macro is necessary to append in-place:
(defmacro concatenatef (s &rest strs)
"Append additional strings to the first string in-place."
`(setf ,s (concatenate 'string ,s ,@strs)))
(defvar *str* "foo")
(concatenatef *str* "bar")
(format T "~a~%" *str*)
(concatenatef *str* "baz" "abc" "def")
(format T "~a~%" *str*)
Output:
foobar
foobarbazabcdef
D
import std.stdio;
void main() {
string s = "Hello";
s ~= " world!";
writeln(s);
}
{{out}}
Hello world!
Dyalect
var s = "foo"
s += "bar"
print(s)
EasyLang
## EchoLisp
```lisp
;; Solution from Common Lisp and Racket
(define-syntax-rule (set-append! str tail)
(set! str (string-append str tail)))
(define name "Albert") → name
(set-append! name " de Jeumont-Schneidre")
name
→ "Albert de Jeumont-Schneidre"
Elena
ELENA 4.x :
import extensions;
import extensions'text;
public program()
{
var s := StringWriter.load("Hello");
s.append:" World";
console.printLine:s.readChar()
}
Elixir
iex(60)> s = "Hello"
"Hello"
iex(61)> s <> " World!"
"Hello World!"
Emacs Lisp
version 1
(defun glue (str1 str2)
(concat str1 str2) )
version 2
(defun glue (str1 str2)
(format "%s%s" str1 str2) )
Eval:
(setq str "Hello, ")
(setq str (glue str "World!") )
(insert str)
Output:
Hello, World!
Erlang
{{out}}
1> S = "Hello".
"Hello"
2> S ++ " world".
"Hello world"
Euphoria
sequence string = "String"
printf(1,"%s\n",{string})
string &= " is now longer\n"
printf(1,"%s",{string})
{{out}}
String
String is now longer
=={{header|F_Sharp|F#}}== Strings are immutable in .NET. To append (to the same variable) the variable has to be declared mutable.
let mutable x = "foo"
x <- x + "bar"
printfn "%s" x
Factor
"Hello, " "world!" append
{{out}}
"Hello, world!"
Falcon
/* Added by Aykayayciti Earl Lamont Montgomery
April 10th, 2018 */
s1, s2 = "Hello", "Foo"
> s1 + " World"
printl(s2 + " bar")
{{out}}
Hello World
Foo bar
[Finished in 0.2s]
Forth
\ Strings in Forth are simply named memory locations
create astring 256 allot \ create a "string"
s" Hello " astring PLACE \ initialize the string
s" World!" astring +PLACE \ append with "+place"
Test at the console
## Fortran
Using deferred length character strings:
```Fortran
program main
character(len=:),allocatable :: str
str = 'hello'
str = str//' world'
write(*,*) str
end program main
FreeBASIC
' FB 1.05.0 Win64
Var s = "String"
s += " append"
Print s
Sleep
{{out}}
String append
Gambas
'''[https://gambas-playground.proko.eu/?gist=0b17e205d56985c8cd1ff108c6fc9ca4 Click this link to run this code]'''
Public Sub Main()
Dim sString As String = "Hello "
sString &= "World!"
Print sString
End
Output:
Hello World!
Genie
[indent=4]
/* String append, in Genie */
init
str:string = "Hello"
str += ", world"
print str
{{out}}
prompt$ valac stringAppend.gs
prompt$ ./stringAppend
Hello, world
GlovePIE
var.string="This is "
var.string+="Sparta!"
debug=var.string
Go
s := "foo"
s += "bar"
String Builder
The first solution redefines the string variable every time. It might be short in code but it uses much CPU cycles. A better way is to use string.Builder but it is not a string. It is more like a buffer which can produce a string. And it really appends the string to the existing variable.
package main
import (
"fmt"
"strings"
)
func main() {
var s strings.Builder
s.WriteString("foo")
s.WriteString("bar")
fmt.Print(s.String())
}
{{out}} foobar
Gosu
// Example 1
var s = "a"
s += "b"
s += "c"
print(s)
// Example 2
print("a" + "b" + "c")
// Example 3
var a = "a"
var b = "b"
var c = "c"
print("${a}${b}${c}")
{{out}}
abc
abc
abc
Groovy
class Append{
static void main(String[] args){
def c="Hello ";
def d="world";
def e=c+d;
println(e);
}
}
{{out}}
Hello world
Haskell
main = putStrLn ("Hello" ++ "World")
=={{header|Icon}} and {{header|Unicon}}== In both languages you can:
procedure main()
s := "foo"
s ||:= "bar"
write(s)
end
Outputs:
->ss
foobar
->
J
s=: 'new'
s
new
s=: s,' value' NB. append is in-place
s
new value
Java
String sa = "Hello";
sa += ", World!";
System.out.println(sa);
StringBuilder ba = new StringBuilder();
ba.append("Hello");
ba.append(", World!");
System.out.println(ba.toString());
{{out}}
Hello, World!
Hello, World!
JavaScript
{{works with|Rhino}} {{works with|SpiderMonkey}}
var s1 = "Hello";
s1 += ", World!";
print(s1);
var s2 = "Goodbye";
// concat() returns the strings together, but doesn't edit existing string
// concat can also have multiple parameters
print(s2.concat(", World!"));
{{out}}
"Hello, World!"
"Goodbye, World!"
jq
jq's + operator can be used to append two strings, and under certain circumstances the += operator can be used as an abbreviation for appending a string to an existing string. For example, all three of the following produce the same output:
"Hello" | . += ", world!"
["Hello"] | .[0] += ", world!" | .[0]
{ "greeting": "Hello"} | .greeting += ", world!" | .greeting
However the += operator cannot be used with jq variables in the conventional manner. One could nevertheless use the technique illustrated by the following:
"Hello" as $a | $a | . += ", world!" as $a | $a
Jsish
From Javascript entry.
/* String append, in Jsish */
var str = 'Hello';
;str += ', world';
var s2 = 'Goodbye';
;s2.concat(', World!');
/*
=!EXPECTSTART!=
str += ', world' ==> Hello, world
s2.concat(', World!') ==> Goodbye, World!
=!EXPECTEND!=
*/
{{out}}
prompt$ jsish --U stringAppend.jsi
str += ', world' ==> Hello, world
s2.concat(', World!') ==> Goodbye, World!
Julia
s = "Hello"
s *= ", world!"
{{out}}
"Hello, world!"
Kotlin
fun main(args: Array<String>) {
var s = "a"
s += "b"
s += "c"
println(s)
println("a" + "b" + "c")
val a = "a"
val b = "b"
val c = "c"
println("$a$b$c")
}
{{out}}
abc
abc
abc
Lasso
local(x = 'Hello')
#x->append(', World!')
#x
{{out}}
Hello, World!
Lingo
str = "Hello"
put " world!" after str
put str
-- "Hello world!"
LiveCode
Livecode has an "after" keyword for this
local str="live"
put "code" after str
Output is "livecode"
Lua
Not possible as strings are immutable. We can demonstrate their immutability using 'self':
function string:show ()
print(self)
end
function string:append (s)
self = self .. s
end
x = "Hi "
x:show()
x:append("there!")
x:show()
{{out}}
Hi
Hi
You can of course concatentate them and store the result in the original variable name but that requires a double reference:
x = "Hi "
x = x .. "there!"
print(x)
{{out}}
Hi there!
M2000 Interpreter
Documents in M2000 are objects with paragraphs.
a$="ok"
a$+="(one)"
Print a$
Document b$
b$="ok"
b$="(one)"
Print b$
{{out}}
ok(one)
ok(one)
Maple
a := "Hello";
b := cat(a, " World");
c := `||`(a, " World");
{{out}}
"Hello"
"Hello World"
"Hello World"
Mathematica
(* mutable strings are not supported *)
s1 = "testing";
s1 = s1 <> " 123";
s1
{{out}}
"testing 123"
MontiLang
|Hello | |world!| swap + print
|Hello | var hello .
|world!| var world .
world hello + print
Neko
The plus operator +, concats strings.
/**
<doc><p>String append in Neko
var str = "Hello" str += ", world" $print(str, "\n")
{{out}}
```txt
prompt$ nekoc string-append.neko
prompt$ neko ./string-append.n
Hello, world
NetRexx
s_ = 'Hello'
s_ = s_', world!'
say s_
{{out}}
Hello, world!
NewLISP
(setq str "foo")
(push "bar" str -1)
; or as an alternative introduced in v.10.1
(extend str "bar")
(println str)
Nim
var str = "123456"
str.add("78") # two ways
str &= "9!" # to append
Objeck
class Append {
function : Main(args : String[]) ~ Nil {
x := "foo";
x->Append("bar");
x->PrintLine();
}
}
OCaml
let () =
let s = Buffer.create 17 in
Buffer.add_string s "Bonjour";
Buffer.add_string s " tout le monde!";
print_endline (Buffer.contents s)
{{out}}
Bonjour tout le monde!
Oforth
StringBuffer new "Hello, " << "World!" << println
PARI/GP
Not supported in GP.
s = "Hello";
s = Str(s, ", world!")
{{out}}
%1 = "Hello, world!"
Pascal
{{works with|Free Pascal|2.6.2}}
program StringAppend;
{$mode objfpc}{$H+}
uses
{$IFDEF UNIX}{$IFDEF UseCThreads}
cthreads,
{$ENDIF}{$ENDIF}
Classes
{ you can add units after this };
var
s: String = 'Hello';
begin
s += ' World !';
WriteLn(S);
ReadLn;
end.
Output:
Hello World !
Perl
my $str = 'Foo';
$str .= 'bar';
print $str;
{{out}}
Foobar
Perl 6
my $str = "foo";
$str ~= "bar";
say $str;
{{out}}
foobar
Phix
string s = "this string" ?s
s &= " is now longer" ?s
{{out}}
"this string"
"this string is now longer"
PicoLisp
(setq Str1 "12345678")
(setq Str1 (pack Str1 "9!"))
(println Str1)
{{out}}
"123456789!"
PL/I
Cat: procedure options (main);
declare s character (100) varying;
s = 'dust ';
s ||= 'bowl';
put (s);
end Cat;
dust bowl
plainTeX
Works with any TeX engine
\def\addtomacro#1#2{\expandafter\def\expandafter#1\expandafter{#1#2}}
\def\foo{Hello}
Initial: \foo
\addtomacro\foo{ world!}
Appended: \foo
\bye
pdf or dvi output:
Initial: Hello
Appended: Hello world!
PowerShell
$str = "Hello, "
$str += "World!"
$str
Hello, World!
PureBasic
S$ = "Hello"
S$ = S$ + " Wo" ;by referencing the string twice
S$ + "rld!" ;by referencing the string once
If OpenConsole()
PrintN(S$)
Print(#CRLF$ + #CRLF$ + "Press ENTER to exit"): Input()
CloseConsole()
EndIf
Sample output:
Hello World!
Python
'''File: String_append.py'''
#!/usr/bin/env python
# -*- coding: utf-8 -*- #
str = "12345678";
str += "9!";
print(str)
{{out}}
123456789!
Racket
;there is no built-in way to set! append in racket
(define mystr "foo")
(set! mystr (string-append mystr " bar"))
(displayln mystr)
;but you can create a quick macro to solve that problem
(define-syntax-rule (set-append! str value)
(set! str (string-append str value)))
(define mymacrostr "foo")
(set-append! mymacrostr " bar")
(displayln mystr)
{{out}}
foo bar
foo bar
REXX
using abutment
s='he'
s=s'llo world!'
Say s
'''output'''
hello world!
using concatenation
s="He"
s=s || 'llo, World!' /*same as: s=s||'llo, World!' */
say s
'''output'''
Hello, World!
Ring
aString1 = "Welcome to the "
aString2 = "Ring Programming Language"
aString3 = aString1 + aString2
see aString3
Robotic
set "$str1" to "Hello "
inc "$str1" by "world!"
* "&$str1&"
end
Ruby
s = "Hello wo"
s += "rld" # new string object
s << "!" # mutates in place, same object
puts s
{{out}}
Hello world!
Rust
use std::ops::Add;
fn main(){
let hello = String::from("Hello world");
println!("{}", hello.add("!!!!"));
}
{{out}} Hello world!!!!
Real append
The first solution doesn't append to the string variable. This solution really appends to the existing variable.
fn main(){
let mut hello = String::from("Hello world");
hello.push_str("!!!!");
println!("{}", hello);
}
{{out}} Hello world!!!!
Scala
An evaluation in Scala worksheet.
var d = "Hello" // Mutables are discouraged //> d : String = Hello
d += ", World!" // var contains a totally new re-instantiationed String
val s = "Hello" // Immutables are recommended //> s : String = Hello
val s1 = s + s //> s1 : String = HelloHello
val f2 = () => " !" //Function assigned to variable
//> f2 : () => String = <function0>
println(s1 + f2()); //> HelloHello !
Seed7
$ include "seed7_05.s7i";
const proc: main is func
local
var string: str is "12345678";
begin
str &:= "9!";
writeln(str);
end func;
{{out}}
123456789!
Sidef
var str = 'Foo';
str += 'bar';
say str;
{{out}}
Foobar
SNOBOL4
s = "Hello"
s = s ", World!"
OUTPUT = s
END
{{out}}
Hello, World!
Stata
sca s="Ars Longa"
sca s=s+" Vita Brevis"
di s
Ars Longa Vita Brevis
Swift
var s = "foo" // "foo"
s += "bar" // "foobar"
print(s) // "foobar"
s.appendContentsOf("baz") // "foobarbaz"
print(s) // "foobarbaz"
Tcl
String concatenation is a fundamental feature of the Tcl language, and there is also an append that makes concatenation even simpler:
set s "he"
set s "${s}llo wo"; # The braces distinguish varname from text to concatenate
append s "rld"
puts $s
{{out}}
hello world
Ursa
decl string str
set str "hello "
# append "world" to str
set str (+ str "world")
# outputs "hello world"
out str endl console
VBA
Function StringAppend()
Dim s As String
s = "foo"
s = s & "bar"
Debug.Print s
End Function
VBScript
s = "Rosetta"
s = s & " Code"
WScript.StdOut.Write s
{{out}}
Rosetta Code
Wart
s <- "12345678"
s <- (s + "9!")
zkl
zkl strings are immutable, but byte blobs are mutable.
var s="foo";
s.append("bar"); //-->new string "foobar", var s unchanged
s+="bar"; //-->new string "foobar", var s modifed to new value
s=Data(Void,"foo"); // byte blob/character blob/text editor buffer
s.append("bar"); // or s+="bar"
s.text; //-->"foobar"
{{omit from|bc|No string operations in bc}} {{omit from|dc|No string operations in dc}}