Copy a string
You are encouraged to solve this task according to the task description, using any language you may know.
This task is about copying a string.
- Task
Where it is relevant, distinguish between copying the contents of a string versus making an additional reference to an existing string.
- Metrics
- Counting
- Word frequency
- Letter frequency
- Jewels and stones
- I before E except after C
- Bioinformatics/base count
- Count occurrences of a substring
- Count how many vowels and consonants occur in a string
- Remove/replace
- XXXX redacted
- Conjugate a Latin verb
- Remove vowels from a string
- String interpolation (included)
- Strip block comments
- Strip comments from a string
- Strip a set of characters from a string
- Strip whitespace from a string -- top and tail
- Strip control codes and extended characters from a string
- Anagrams/Derangements/shuffling
- Word wheel
- ABC problem
- Sattolo cycle
- Knuth shuffle
- Ordered words
- Superpermutation minimisation
- Textonyms (using a phone text pad)
- Anagrams
- Anagrams/Deranged anagrams
- Permutations/Derangements
- Find/Search/Determine
- ABC words
- Odd words
- Word ladder
- Semordnilap
- Word search
- Wordiff (game)
- String matching
- Tea cup rim text
- Alternade words
- Changeable words
- State name puzzle
- String comparison
- Unique characters
- Unique characters in each string
- Extract file extension
- Levenshtein distance
- Palindrome detection
- Common list elements
- Longest common suffix
- Longest common prefix
- Compare a list of strings
- Longest common substring
- Find common directory path
- Words from neighbour ones
- Change e letters to i in words
- Non-continuous subsequences
- Longest common subsequence
- Longest palindromic substrings
- Longest increasing subsequence
- Words containing "the" substring
- Sum of the digits of n is substring of n
- Determine if a string is numeric
- Determine if a string is collapsible
- Determine if a string is squeezable
- Determine if a string has all unique characters
- Determine if a string has all the same characters
- Longest substrings without repeating characters
- Find words which contains all the vowels
- Find words which contain the most consonants
- Find words which contains more than 3 vowels
- Find words whose first and last three letters are equal
- Find words with alternating vowels and consonants
- Formatting
- Substring
- Rep-string
- Word wrap
- String case
- Align columns
- Literals/String
- Repeat a string
- Brace expansion
- Brace expansion using ranges
- Reverse a string
- Phrase reversals
- Comma quibbling
- Special characters
- String concatenation
- Substring/Top and tail
- Commatizing numbers
- Reverse words in a string
- Suffixation of decimal numbers
- Long literals, with continuations
- Numerical and alphabetical suffixes
- Abbreviations, easy
- Abbreviations, simple
- Abbreviations, automatic
- Song lyrics/poems/Mad Libs/phrases
- Mad Libs
- Magic 8-ball
- 99 bottles of beer
- The Name Game (a song)
- The Old lady swallowed a fly
- The Twelve Days of Christmas
- Tokenize
- Text between
- Tokenize a string
- Word break problem
- Tokenize a string with escaping
- Split a character string based on change of character
- Sequences
11l
V src = ‘hello’
V dst = copy(src)
360 Assembly
To copy a string, we use an MVC (Move Character). To make a reference to a string, we use a LA (Load Address).
* Duplicate a string
MVC A,=CL64'Hello' a='Hello'
MVC B,A b=a memory copy
MVC A,=CL64'Goodbye' a='Goodbye'
XPRNT A,L'A print a
XPRNT B,L'B print b
...
* Make reference to a string a string
MVC A,=CL64'Hi!' a='Hi!'
LA R1,A r1=@a set pointer
ST R1,REFA refa=@a store pointer
XPRNT A,L'A print a
XPRNT 0(R1),L'A print %refa
...
A DS CL64 a
B DS CL64 b
REFA DS A @a
6502 Assembly
source equ $10 ;$10 was chosen arbitrarily
source_hi equ source+1 ;the high byte MUST be after the low byte, otherwise this will not work.
dest equ $12
dest_hi equ dest+1
LDA #<MyString ;get the low byte of &MyString
STA source
LDA #>MyString ;get the high byte
STA source_hi ;we just created a "shallow reference" to an existing string.
;As it turns out, this is a necessary step to do a deep copy.
LDA #<RamBuffer
STA dest
LDA #>RamBuffer
STA dest_hi
strcpy:
;assumes that RamBuffer is big enough to hold the source string, and that the memory ranges do not overlap.
;if you've ever wondered why C's strcpy is considered "unsafe", this is why.
LDY #0
.again:
LDA (source),y
STA (dest),y
BEQ .done
INY
BNE .again ;exit after 256 bytes copied or the null terminator is reached, whichever occurs first.
RTS
MyString:
byte "hello",0
RamBuffer:
byte 0,0,0,0,0,0
68000 Assembly
Making a reference to an existing string is simple. Just load its memory location into an address register.
myString: DC.B "HELLO WORLD",0
EVEN
LEA myString,A3
Copying a string involves a little more work:
StringRam equ $100000
myString: DC.B "HELLO WORLD",0
EVEN
LEA myString,A3
LEA StringRam,A4
CopyString:
MOVE.B (A3)+,D0
MOVE.B D0,(A4)+ ;we could have used "MOVE.B (A3)+,(A4)+" but this makes it easier to check for the terminator.
BEQ Terminated
BRA CopyString
Terminated: ;the null terminator is already stored along with the string itself, so we are done.
;program ends here.
8086 Assembly
The technique varies depending on whether you just want a new reference to the old string or to actually duplicate it in RAM. Strangely, this is one of the few things that's actually easier to do correctly in assembly than in high-level languages - it's very unlikely you'll do the wrong one by accident.
Making a new reference
This technique is useful if you wish to create a struct/record that needs to be able to retrieve a string quickly. All you need to do is get a pointer to the desired string and store it in RAM.
.model small
.stack 1024
.data
myString byte "Hello World!",0 ; a null-terminated string
myStruct word 0
.code
mov ax,@data
mov ds,ax ;load data segment into DS
mov bx,offset myString ;get the pointer to myString
mov word ptr [ds:myStruct],bx
mov ax,4C00h
int 21h ;quit program and return to DOS
Creating a "deep copy"
This method will actually make a byte-for-byte copy somewhere else in RAM.
.model small
.stack 1024
.data
myString byte "Hello World!",0 ; a null-terminated string
StringRam byte 256 dup (0) ;256 null bytes
.code
mov ax,@data
mov ds,ax ;load data segment into DS
mov es,ax ;also load it into ES
mov si,offset myString
mov di,offset StringRam
mov cx,12 ;length of myString
cld ;make MOVSB auto-increment rather than auto-decrement (I'm pretty sure DOS begins with
;the direction flag cleared but just to be safe)
rep movsb ;copies 12 bytes from [ds:si] to [es:di]
mov al,0 ;create a null terminator
stosb ;store at the end. (It's already there since we initialized StringRam to zeroes, but you may need to do this depending
;on what was previously stored in StringRam, if you've copied a string there already.
mov ax,4C00h
int 21h ;quit program and return to DOS
AArch64 Assembly
/* ARM assembly AARCH64 Raspberry PI 3B */
/* program copystr64.s */
/*******************************************/
/* Constantes file */
/*******************************************/
/* for this file see task include a file in language AArch64 assembly*/
.include "../includeConstantesARM64.inc"
/*******************************************/
/* Initialized data */
/*******************************************/
.data
szString: .asciz "ABCDEFGHIJKLMNOPQRSTUVWXYZ\n"
/*******************************************/
/* UnInitialized data */
/*******************************************/
.bss
.align 4
qPtString: .skip 8
szString1: .skip 80
/*******************************************/
/* code section */
/*******************************************/
.text
.global main
main: // entry of program
// display start string
ldr x0,qAdrszString
bl affichageMess
// copy pointer string
ldr x0,qAdrszString
ldr x1,qAdriPtString
str x0,[x1]
// control
ldr x1,qAdriPtString
ldr x0,[x1]
bl affichageMess
// copy string
ldr x0,qAdrszString
ldr x1,qAdrszString1
1:
ldrb w2,[x0],1 // read one byte and increment pointer one byte
strb w2,[x1],1 // store one byte and increment pointer one byte
cmp x2,#0 // end of string ?
bne 1b // no -> loop
// control
ldr x0,qAdrszString1
bl affichageMess
100: // standard end of the program */
mov x0,0 // return code
mov x8,EXIT // request to exit program
svc 0 // perform the system call
qAdrszString: .quad szString
qAdriPtString: .quad qPtString
qAdrszString1: .quad szString1
/********************************************************/
/* File Include fonctions */
/********************************************************/
/* for this file see task include a file in language AArch64 assembly */
.include "../includeARM64.inc"
ABAP
data: lv_string1 type string value 'Test',
lv_string2 type string.
lv_string2 = lv_string1.
Inline Declaration
DATA(string1) = |Test|.
DATA(string2) = string1.
Action!
PROC Main()
CHAR ARRAY str1,str2,str3(10)
str1="Atari"
str2=str1
SCopy(str3,str1)
PrintF(" base=%S%E",str1)
PrintF("alias=%S%E",str2)
PrintF(" copy=%S%E",str3)
PutE()
SCopy(str1,"Action!")
PrintF(" base=%S%E",str1)
PrintF("alias=%S%E",str2)
PrintF(" copy=%S%E",str3)
RETURN
- Output:
Screenshot from Atari 8-bit computer
base=Atari alias=Atari copy=Atari base=Action! alias=Action! copy=Atari
ActionScript
Strings are immutable in ActionScript, and can safely be assigned with the assignment operator, much as they can in Java.[1]
var str1:String = "Hello";
var str2:String = str1;
Ada
Ada provides three different kinds of strings. The String type is a fixed length string. The Bounded_String type is a string with variable length up to a specified maximum size. The Unbounded_String type is a variable length string with no specified maximum size. The Bounded_String type behaves a lot like C strings, while the Unbounded_String type behaves a lot like the C++ String class.
Fixed Length String Copying.
Src : String := "Hello";
Dest : String := Src;
Ada provides the ability to manipulate slices of strings.
Src : String := "Rosetta Stone";
Dest : String := Src(1..7); -- Assigns "Rosetta" to Dest
Dest2 : String := Src(9..13); -- Assigns "Stone" to Dest2
Bounded Length String Copying
-- Instantiate the generic package Ada.Strings.Bounded.Generic_Bounded_Length with a maximum length of 80 characters
package Flexible_String is new Ada.Strings.Bounded.Generic_Bounded_Length(80);
use Flexible_String;
Src : Bounded_String := To_Bounded_String("Hello");
Dest : Bounded_String := Src;
Ada Bounded_String type provides a number of functions for dealing with slices.
Unbounded Length String Copying
-- The package Ada.Strings.Unbounded contains the definition of the Unbounded_String type and all its methods
Src : Unbounded_String := To_Unbounded_String("Hello");
Dest : Unbounded_String := Src;
Aime
The intrinsic text type is immediate, immutable and cannot be referred more than once.
Copying an intrinsic string:
text s, t;
t = "Rosetta";
s = t;
Data of the non intrinsic byte array type can be referred more than once. Copying a binary array of bytes:
data s, t;
# Copy -t- into -s-
b_copy(s, t);
# Set -s- as a reference of the object -t- is pointing
b_set(s, t);
# or:
s = t;
ALGOL 68
In ALGOL 68 strings are simply flexible length arrays of CHAR;
(
STRING src:="Hello", dest;
dest:=src
)
ALGOL W
begin
% strings are (fixed length) values in algol W. Assignment makes a copy %
string(10) a, copyOfA;
a := "some text";
copyOfA := a;
% assignment to a will not change copyOfA %
a := "new value";
write( a, copyOfA )
end.
- Output:
new value some text
Apex
In Apex, Strings are a primitive data type
String original = 'Test';
String cloned = original;
//"original == cloned" is true
cloned += ' more';
//"original == cloned" is false
AppleScript
set src to "Hello"
set dst to src
ARM Assembly
/* ARM assembly Raspberry PI */
/* program copystr.s */
/* Constantes */
.equ STDOUT, 1 @ Linux output console
.equ EXIT, 1 @ Linux syscall
.equ WRITE, 4 @ Linux syscall
/* Initialized data */
.data
szString: .asciz "ABCDEFGHIJKLMNOPQRSTUVWXYZ\n"
/* UnInitialized data */
.bss
.align 4
iPtString: .skip 4
szString1: .skip 80
/* code section */
.text
.global main
main: /* entry of program */
push {fp,lr} /* saves 2 registers */
@ display start string
ldr r0,iAdrszString
bl affichageMess
@ copy pointer string
ldr r0,iAdrszString
ldr r1,iAdriPtString
str r0,[r1]
@ control
ldr r1,iAdriPtString
ldr r0,[r1]
bl affichageMess
@ copy string
ldr r0,iAdrszString
ldr r1,iAdrszString1
1:
ldrb r2,[r0],#1 @ read one byte and increment pointer one byte
strb r2,[r1],#1 @ store one byte and increment pointer one byte
cmp r2,#0 @ end of string ?
bne 1b @ no -> loop
@ control
ldr r0,iAdrszString1
bl affichageMess
100: /* standard end of the program */
mov r0, #0 @ return code
pop {fp,lr} @restaur 2 registers
mov r7, #EXIT @ request to exit program
swi 0 @ perform the system call
iAdrszString: .int szString
iAdriPtString: .int iPtString
iAdrszString1: .int szString1
/******************************************************************/
/* display text with size calculation */
/******************************************************************/
/* r0 contains the address of the message */
affichageMess:
push {fp,lr} /* save registres */
push {r0,r1,r2,r7} /* save others 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" */
swi #0 /* call systeme */
pop {r0,r1,r2,r7} /* restaur others registers */
pop {fp,lr} /* restaur des 2 registres */
bx lr /* return */
Arturo
a: new "Hello"
b: a ; reference the same string
; changing one string in-place
; will change both strings
'b ++ "World"
print b
print a
c: "Hello"
d: new c ; make a copy of the older string
; changing one string in-place
; will change only the string in question
'd ++ "World"
print d
print c
- Output:
HelloWorld HelloWorld HelloWorld Hello
Asymptote
string src, dst;
src = "Hello";
dst = src;
src = " world...";
write(dst, src);
AutoHotkey
src := "Hello"
dst := src
AutoIt
$Src= "Hello"
$dest = $Src
AWK
BEGIN {
a = "a string"
b = a
sub(/a/, "X", a) # modify a
print b # b is a copy, not a reference to...
}
Axe
Lbl STRCPY
r₁→S
While {r₂}
{r₂}→{r₁}
r₁++
r₂++
End
0→{r₁}
S
Return
Babel
To copy a string in Babel is the same as copying any other object. Use the cp operator to make a deep-copy.
babel> "Hello, world\n" dup cp dup 0 "Y" 0 1 move8
babel> << <<
Yello, world
Hello, world
BASIC
src$ = "Hello" dst$ = src$
Applesoft BASIC
100 DEF FN P(A) = PEEK (A) + PEEK(A + 1) * 256 : FOR I = FN P(105) TO FN P(107) - 1 STEP 7 : ON PEEK(I + 1) < 128 OR PEEK(I) > 127 GOTO 130 : ON LEFT$(P$, 1) <> CHR$(PEEK(I)) GOTO 130
110 IF LEN(P$) > 1 THEN ON PEEK(I + 1) = 128 GOTO 130 : IF MID$(P$, 2, 1) <> CHR$(PEEK(I + 1) - 128) GOTO 130
120 POKE I + 4, P / 256 : POKE I + 3, P - PEEK(I + 4) * 256 : RETURN
130 NEXT I : STOP
S$ = "HELLO" : REM S$ IS THE ORIGINAL STRING
C$ = S$ : REM C$ IS THE COPY
P$ = "S" : P = 53637 : GOSUB 100"POINT STRING S AT SOMETHING ELSE
?S$
?C$
BaCon
Strings by value or by reference
Strings can be stored by value or by reference. By value means that a copy of the original string is stored in a variable. This happens automatically when when a string variable name ends with the '$' symbol.
Sometimes it may be necessary to refer to a string by reference. In such a case, simply declare a variable name as STRING but omit the '$' at the end. Such a variable will point to the same memory location as the original string. The following examples should show the difference between by value and by reference.
When using string variables by value:
a$ = "I am here"
b$ = a$
a$ = "Hello world..."
PRINT a$, b$
This will print "Hello world...I am here". The variables point to their individual memory areas so they contain different strings. Now consider the following code:
a$ = "Hello world..."
LOCAL b TYPE STRING
b = a$
a$ = "Goodbye..."
PRINT a$, b
This will print "Goodbye...Goodbye..." because the variable 'b' points to the same memory area as 'a$'.
BASIC256
src$ = "Hello"
dst$ = src$
src$ = " world..."
print dst$; src$
QBasic
src$ = "Hello" ' is the original string
dst$ = src$ ' is the copy
src$ = " world..."
PRINT dst$; src$
True BASIC
LET src$ = "Hello"
LET dst$ = src$
LET src$ = " world..."
PRINT dst$; src$
END
Yabasic
src$ = "Hello"
dst$ = src$
src$ = " world..."
print dst$, src$
end
Commodore BASIC
10 A$ = "HELLO"
20 REM COPY CONTENTS OF A$ TO B$
30 B$ = A$
40 REM CHANGE CONTENTS OF A$
50 A$ = "HI"
60 REM DISPLAY CONTENTS
70 PRINT A$, B$
Commodore BASIC can't do pointers or 'reference to'
Sinclair ZX81 BASIC
Creating a new reference to an existing string is not possible, or at least not easy. (You could probably do it with PEEK
s and POKE
s.) This program demonstrates that an assignment statement copies a string, by showing that the two strings can afterwards be independently modified.
10 LET A$="BECAUSE I DO NOT HOPE TO TURN AGAIN"
20 LET B$=A$
30 LET A$=A$( TO 21)
40 PRINT B$
50 PRINT A$
60 LET B$=A$+B$(22 TO 29)
70 PRINT B$
- Output:
BECAUSE I DO NOT HOPE TO TURN AGAIN BECAUSE I DO NOT HOPE BECAUSE I DO NOT HOPE TO TURN
Batch File
Since the only variables are environment variables, creating a string copy is fairly straightforward:
set src=Hello
set dst=%src%
BBC BASIC
source$ = "Hello, world!"
REM Copy the contents of a string:
copy$ = source$
PRINT copy$
REM Make an additional reference to a string:
!^same$ = !^source$
?(^same$+4) = ?(^source$+4)
?(^same$+5) = ?(^source$+5)
PRINT same$
Binary Lambda Calculus
In BLC, every value is immutable, including byte-strings. So one never needs to copy them; references are shared.
BQN
BQN strings are character arrays. Like all other types of arrays, they are immutable.
String copying in BQN is left to be defined by the implementation, but CBQN and mlochbaum/BQN(main implementations) copy only the reference until the original source is modified.
a ← "Hello"
b ← a
•Show a‿b
a ↩ "hi"
•Show a‿b
⟨ "Hello" "Hello" ⟩
⟨ "hi" "Hello" ⟩
Bracmat
Because in Bracmat strings are unalterable, you never want to copy a string.
Still, you will obtain a copy of a string by overflowing the reference counter of the string.
(Currently, reference counters on strings and on most operators are 10 bits wide.
The =
operator has a much wider 'inexhaustible' reference counter, because it anchors alterable objects.)
Still, you won't be able to test whether you got the original or a copy other than by looking at overall memory usage of the Bracmat program at the OS-level or by closely timing comparison operations.
You obtain a new reference to a string or a copy of the string by simple assignment using the =
or the :
operator:
abcdef:?a;
!a:?b;
c=abcdef;
!c:?d;
!a:!b { variables a and b are the same and probably referencing the same string }
!a:!d { variables a and d are also the same but not referencing the same string }
C
#include <stdlib.h> /* exit(), free() */
#include <stdio.h> /* fputs(), perror(), printf() */
#include <string.h>
int
main()
{
size_t len;
char src[] = "Hello";
char dst1[80], dst2[80];
char *dst3, *ref;
/*
* Option 1. Use strcpy() from <string.h>.
*
* DANGER! strcpy() can overflow the destination buffer.
* strcpy() is only safe if the source string is shorter than
* the destination buffer. We know that "Hello" (6 characters
* with the final '\0') easily fits in dst1 (80 characters).
*/
strcpy(dst1, src);
/*
* Option 2. Use strlen() and memcpy() from <string.h>, to copy
* strlen(src) + 1 bytes including the final '\0'.
*/
len = strlen(src);
if (len >= sizeof dst2) {
fputs("The buffer is too small!\n", stderr);
exit(1);
}
memcpy(dst2, src, len + 1);
/*
* Option 3. Use strdup() from <string.h>, to allocate a copy.
*/
dst3 = strdup(src);
if (dst3 == NULL) {
/* Failed to allocate memory! */
perror("strdup");
exit(1);
}
/* Create another reference to the source string. */
ref = src;
/* Modify the source string, not its copies. */
memset(src, '-', 5);
printf(" src: %s\n", src); /* src: ----- */
printf("dst1: %s\n", dst1); /* dst1: Hello */
printf("dst2: %s\n", dst2); /* dst2: Hello */
printf("dst3: %s\n", dst3); /* dst3: Hello */
printf(" ref: %s\n", ref); /* ref: ----- */
/* Free memory from strdup(). */
free(dst3);
return 0;
}
#include <stdlib.h> /* exit() */
#include <stdio.h> /* fputs(), printf() */
#include <string.h>
int
main()
{
char src[] = "Hello";
char dst[80];
/* Use strlcpy() from <string.h>. */
if (strlcpy(dst, src, sizeof dst) >= sizeof dst) {
fputs("The buffer is too small!\n", stderr);
exit(1);
}
memset(src, '-', 5);
printf("src: %s\n", src); /* src: ----- */
printf("dst: %s\n", dst); /* dst: Hello */
return 0;
}
Versión 2, using Gadget library.
Link:
https://github.com/DanielStuardo/Gadget
#include <gadget/gadget.h>
LIB_GADGET_START
Main
String v, w = "this message is a message";
Let( v, "Hello world!");
Print "v = %s\nw = %s\n\n", v,w;
Get_fn_let( v, Upper(w) );
Print "v = %s\nw = %s\n\n", v,w;
Stack{
Store ( v, Str_tran_last( Upper(w), "MESSAGE", "PROOF" ) );
}Stack_off;
Print "v = %s\nw = %s\n\n", v,w;
Free secure v, w;
End
- Output:
v = Hello world! w = this message is a message v = THIS MESSAGE IS A MESSAGE w = this message is a message v = THIS MESSAGE IS A PROOF w = this message is a message
C#
string src = "Hello";
string dst = src;
C++
#include <iostream>
#include <string>
int main( ) {
std::string original ("This is the original");
std::string my_copy = original;
std::cout << "This is the copy: " << my_copy << std::endl;
original = "Now we change the original! ";
std::cout << "my_copy still is " << my_copy << std::endl;
}
Clojure
(let [s "hello"
s1 s]
(println s s1))
COBOL
MOVE "Hello" TO src
MOVE src TO dst
ColdFusion
In ColdFusion, only complex data types (structs, objects, etc.) are passed by reference. Hence, any string copy operations are by value.
<cfset stringOrig = "I am a string." />
<cfset stringCopy = stringOrig />
Common Lisp
(let* ((s1 "Hello") ; s1 is a variable containing a string
(s1-ref s1) ; another variable with the same value
(s2 (copy-seq s1))) ; s2 has a distinct string object with the same contents
(assert (eq s1 s1-ref)) ; same object
(assert (not (eq s1 s2))) ; different object
(assert (equal s1 s2)) ; same contents
(fill s2 #\!) ; overwrite s2
(princ s1)
(princ s2)) ; will print "Hello!!!!!"
Component Pascal
VAR
str1: ARRAY 128 OF CHAR;
str2: ARRAY 32 OF CHAR;
str3: ARRAY 25 OF CHAR;
...
str1 := "abcdefghijklmnopqrstuvwxyz";
str3 := str1; (* don't compile, incompatible assignement *)
str3 := str1$; (* runtime error, string too long *)
str2 := str1$; (* OK *)
Computer/zero Assembly
Assuming a string to be a zero-terminated array of bytes, this program takes a string beginning at address src and makes a copy of it beginning at address dest. As an example, we copy the string "Rosetta".
ldsrc: LDA src
stdest: STA dest
BRZ done ; 0-terminated
LDA ldsrc
ADD one
STA ldsrc
LDA stdest
ADD one
STA stdest
JMP ldsrc
done: STP
one: 1
src: 82 ; ASCII
111
115
101
116
116
97
0
dest:
Crystal
s1 = "Hello"
s2 = s1
D
void main() {
string src = "This is a string";
// copy contents:
auto dest1 = src.idup;
// copy contents to mutable char array
auto dest2 = src.dup;
// copy just the fat reference of the string
auto dest3 = src;
}
dc
[a string] # push "a string" on the main stack
d # duplicate the top value
f # show the current contents of the main stack
- Output:
a string a string
Delphi
Delphi strings are reference counted with copy on write semantics.
program CopyString;
{$APPTYPE CONSOLE}
var
s1: string;
s2: string;
begin
s1 := 'Goodbye';
s2 := s1; // S2 points at the same string as S1
s2 := s2 + ', World!'; // A new string is created for S2
Writeln(s1);
Writeln(s2);
end.
- Output:
Goodbye Goodbye, World!
DWScript
DWScript strings are value-type, from the language point of view, you can't have a reference to a String, no more than you can have a reference to an Integer or a Float (unless you wrap in an object of course).
Internally they're transparently implemented via either immutable reference or copy-on-write.
Dyalect
Strings in Dyalect are immutable:
var src = "foobar"
var dst = src
Déjà Vu
In Déjà Vu, strings are immutable, so there really isn't a good reason to copy them. As such, no standard way of doing so is provided. However, one can still create a copy of a string by concatenating it with an empty string.
local :orgininal "this is the original"
local :scopy concat( original "" )
!. scopy
- Output:
"this is the original"
E
E is a pass-references-by-value object-oriented language, and strings are immutable, so there is never a need for or benefit from copying a string.
Various operations, such as taking the substring (run) from the beginning to the end (someString.run(0)
) might create a copy,
but this is not guaranteed.
EasyLang
a$ = "hello"
b$ = a$
print b$
EchoLisp
Strings are immutable. A copy will return the same object.
(define-syntax-rule (string-copy s) (string-append s)) ;; copy = append nothing
→ #syntax:string-copy
(define s "abc")
(define t (string-copy s))
t → "abc"
(eq? s t) → #t ;; same reference, same object
EDSAC order code
Expects the final character of a string to be marked with a 1 in the least significant bit, as in Hello world/Line printer#EDSAC order code. The source string should be loaded at θ+34; it is copied into storage tank 6. The copy is then printed out.
[ Copy a string
=============
A program for the EDSAC
Copies the source string into storage
tank 6, which is assumed to be free,
and then prints it from there
Works with Initial Orders 2 ]
T56K
GK
[ 0 ] A34@ [ copy the string ]
[ 1 ] T192F
[ 2 ] H34@
C32@
S32@
E17@
T31@
A@
A33@
T@
A1@
A33@
T1@
A2@
A33@
T2@
E@
[ 17 ] O192F [ print the copy ]
[ 18 ] H192F
C32@
S32@
E30@
T31@
A17@
A33@
T17@
A18@
A33@
T18@
E17@
[ 30 ] ZF
[ 31 ] PF
[ 32 ] PD
[ 33 ] P1F
[ 34 ] *F
RF
OF
SF
EF
TF
TF
AF
!F
CF
OF
DF
ED
EZPF
- Output:
ROSETTA CODE
Elena
var src := "Hello";
var dst := src; // copying the reference
var copy := src.clone(); // copying the content
Elixir
src = "Hello"
dst = src
Emacs Lisp
(let* ((str1 "hi")
(str1-ref str1)
(str2 (copy-sequence str1)))
(eq str1 str1-ref) ;=> t
(eq str1 str2) ;=> nil
(equal str1 str1-ref) ;=> t
(equal str1 str2)) ;=> t
EMal
in EMal strings are mutable
text original = "Yellow world"
text ref = original # copying the reference
text copied = *original # copying the content
original[0] = "H" # texts are indexable and mutable
original[5] = ","
ref.append("!") # texts are coercible and growable
copied += "?"
^|
| original == ref == "Hello, world!"
| copied == "Yellow world?"
|^
Erlang
Src = "Hello".
Dst = Src.
Euphoria
Arrays in many languages are constrained to have a fixed number of elements, and those elements must all be of the same type. Euphoria eliminates both of those restrictions by defining all arrays (sequences) as a list of zero or more Euphoria objects whose element count can be changed at any time. When you retrieve a sequence element, it is not guaranteed to be of any type. You, as a programmer, need to check that the retrieved data is of the type you'd expect, Euphoria will not. The only thing it will check is whether an assignment is legal. For example, if you try to assign a sequence to an integer variable, Euphoria will complain at the time your code does the assignment.
sequence first = "ABC"
sequence newOne = first
F#
.NET strings are immutable, so it is usually not useful to make a deep copy.
However if needed, it is possible using a static method of the System.String
type:
let str = "hello"
let additionalReference = str
let deepCopy = System.String.Copy( str )
printfn "%b" <| System.Object.ReferenceEquals( str, additionalReference ) // prints true
printfn "%b" <| System.Object.ReferenceEquals( str, deepCopy ) // prints false
Factor
Factor strings are mutable but not growable. Strings will be immutable in a future release.
"This is a mutable string." dup ! reference
"Let's make a deal!" dup clone ! copy
"New" " string" append . ! new string
"New string"
Factor string buffers (sbufs) are mutable and growable.
SBUF" Grow me!" dup " OK." append
SBUF" Grow me! OK."
Convert a string buffer to a string.
SBUF" I'll be a string someday." >string .
"I'll be a string someday."
Forth
Forth strings are generally stored in memory as prefix counted string, where the first byte contains the string length. However, on the stack they are most often represented as <addr cnt> pairs. Thus the way you copy a string depends on where the source string comes from:
\ Allocate two string buffers
create stringa 256 allot
create stringb 256 allot
\ Copy a constant string into a string buffer
s" Hello" stringa place
\ Copy the contents of one string buffer into another
stringa count stringb place
Fortran
str2 = str1
Because Fortran uses fixed length character strings if str1 is shorter than str2 then str2 is padded out with trailing spaces. If str1 is longer than str2 it is truncated to fit.
FreeBASIC
' FB 1.05.0 Win64
Dim s As String = "This is a string"
Dim t As String = s
' a separate copy of the string contents has been made as can be seen from the addresses
Print s, StrPtr(s)
Print t, StrPtr(t)
' to refer to the same string a pointer needs to be used
Dim u As String Ptr = @s
Print
Print *u, StrPtr(*u)
Sleep
- Output:
This is a string 10623504 This is a string 10623552 This is a string 10623504
Frink
Strings are immutable after construction, so "copying" a string just creates a new reference to a string. All string manipulation routines return a new string.
a = "Monkey"
b = a
FutureBasic
include "NSLog.incl"
CFStringRef original, copy
original = @"Hello!"
copy = fn StringWithString( original )
NSLog( @"%@", copy )
HandleEvents
Output:
Hello!
Gambas
Note that the DIM statement is required in Gambas.
Click this link to run this code
Public Sub main()
Dim src As String
Dim dst As String
src = "Hello"
dst = src
Print src
Print dst
End
GAP
#In GAP strings are lists of characters. An affectation simply copy references
a := "more";
b := a;
b{[1..4]} := "less";
a;
# "less"
# Here is a true copy
a := "more";
b := ShallowCopy(a);
b{[1..4]} := "less";
a;
# "more"
GML
src = "string";
dest = src;
Go
Just use assignment:
src := "Hello"
dst := src
Strings in Go are immutable. Because of this, there is no need to distinguish between copying the contents and making an additional reference. Technically, Go strings are immutable byte slices. A slice is an object that contains a reference to an underlying array. In the assignment shown above, a new slice object is created for dst. Its internal reference is likely to point to the same underlying array as src, but the language does not specify this behavior or make any guarantees about it.
package main import "fmt" func main() { // creature string var creature string = "shark" // point to creature var pointer *string = &creature // creature string fmt.Println("creature =", creature) // creature = shark // creature location in memory fmt.Println("pointer =", pointer) // pointer = 0xc000010210 // creature through the pointer fmt.Println("*pointer =", *pointer) // *pointer = shark // set creature through the pointer *pointer = "jellyfish" // creature through the pointer fmt.Println("*pointer =", *pointer) // *pointer = jellyfish // creature string fmt.Println("creature =", creature) // creature = jellyfish }
Groovy
The dynamics of references and object creation are very much the same as in Java. However, the meaning of the equality (==) operator is different in Groovy, so we show those differences here, even though they are not relevant to the actual copying.
Example and counter-example:
def string = 'Scooby-doo-bee-doo' // assigns string object to a variable reference
def stringRef = string // assigns another variable reference to the same object
def stringCopy = new String(string) // copies string value into a new object, and assigns to a third variable reference
Test Program:
assert string == stringRef // they have equal values (like Java equals(), not like Java ==)
assert string.is(stringRef) // they are references to the same objext (like Java ==)
assert string == stringCopy // they have equal values
assert ! string.is(stringCopy) // they are references to different objects (like Java !=)
Caveat Lector: Strings are immutable objects in Groovy, so it is wasteful and utterly unnecessary to ever make copies of them within a Groovy program.
GUISS
Start.Programs,Accessories,Notepad,
Type:Hello world[pling],Highlight:Hello world[pling],
Menu,Edit,Copy,Menu,Edit,Paste
Harbour
cSource := "Hello World"
cDestination := cSource
Haskell
In Haskell, every value is immutable, including Strings. So one never needs to copy them; references are shared.
HicEst
src = "Hello World"
dst = src
i
//Strings are immutable in 'i'.
software {
a = "Hello World"
b = a //This copies the string.
a += "s"
print(a)
print(b)
}
Icon and Unicon
Strings in Icon are immutable.
Under the covers 'b' is created as a reference to the same string as 'a'; the sub-string assignment creates a new copy of the string. However, there is no way to tell this in the language. While most of the time this is transparent, programs that create very long strings through repeated concatenation need to avoid generating intermediate strings. Instead using a list and concatenating at the last minute can perform much better.
Note that strings are indicated using double quotes. However, single quotes are another type called character sets or csets.
J
src =: 'hello'
dest =: src
J has copy-on-write semantics.
So both src
and dest
are references to the same memory, until src
changes, at which time dest
retains a copy of the original value of src
.
Java
In Java, Strings are immutable, so it doesn't make that much difference to copy it.
String src = "Hello";
String newAlias = src;
String strCopy = new String(src);
//"newAlias == src" is true
//"strCopy == src" is false
//"strCopy.equals(src)" is true
Instead, maybe you want to create a StringBuffer
(mutable string) from an existing String or StringBuffer:
StringBuffer srcCopy = new StringBuffer("Hello");
JavaScript
Objects can be copied in JavaScript via simple reassignment. Changes to the properties of one will be reflected in the other:
var container = {myString: "Hello"};
var containerCopy = container; // Now both identifiers refer to the same object
containerCopy.myString = "Goodbye"; // container.myString will also return "Goodbye"
If you copy property values with reassignment, such as properties of the global object (window
in browsers), only the value will be copied and not the reference
var a = "Hello";
var b = a; // Same as saying window.b = window.a
b = "Goodbye" // b contains a copy of a's value and a will still return "Hello"
Joy
"hello" dup
Strings are immutable.
jq
jq is a functional language and all data types, including strings, are immutable. If a string were to be copied (e.g. by exploding and imploding it), the resultant string would be equal in all respects to the original, and from the jq programmer's perspective, the two would be identical.
jq does however have a type of variable, though their values actually don't change -- they are just context-dependent. For example, consider the sequence of steps in the following function:
def demo:
"abc" as $s # assignment of a string to a variable
| $s as $t # $t points to the same string as $s
| "def" as $s # This $s shadows the previous $s
| $t # $t still points to "abc"
;
demo
- Output:
"abc"
Julia
Strings are immutable in Julia. Assignment of one string valued variable to another is effectively a copy, as subsequent changes to either variable have no effect on the other.
s = "Rosetta Code"
t = s
println("s = \"", s, "\" and, after \"t = s\", t = \"", t, "\"")
s = "Julia at "*s
println("s = \"", s, "\" and, after this change, t = \"", t, "\"")
- Output:
s = "Rosetta Code" and, after "t = s", t = "Rosetta Code" s = "Julia at Rosetta Code" and, after this change, t = "Rosetta Code"
KonsolScript
Var:String str1 = "Hello";
Var:String str2 = str1;
Kotlin
val s = "Hello"
val alias = s // alias === s
val copy = "" + s // copy !== s
LabVIEW
In LabVIEW, one can simply wire an input to more than one output.
This image is a VI Snippet, an executable image of LabVIEW code. The LabVIEW version is shown on the top-right hand corner. You can download it, then drag-and-drop it onto the LabVIEW block diagram from a file browser, and it will appear as runnable, editable code.
Lambdatalk
{def S1 hello world} // set S1 to "hello world"
-> S1
{S1} // get the value of S1
-> hello world
{def S2 S1} // define S2 as S1
-> S2
{S2} // the value of S2 is S1
-> S1
{{S2}} // get the value of the value of S2
-> hello world
{def S3 {S1}} // set S3 to the value of S1
-> S3
{S3} // get the value of S3
-> hello world
Lang5
'hello dup
Lasso
While other datatypes like arrays require ->asCopy & ->asCopyDeep methods, assigning strings creates a copy, not a reference, as is seen below.
local(x = 'I saw a rhino!')
local(y = #x)
#x //I saw a rhino!
'\r'
#y //I saw a rhino!
'\r\r'
#x = 'I saw one too'
#x //I saw one too
'\r'
#y //I saw a rhino!
'\r\r'
#y = 'it was grey.'
#x //I saw one too
'\r'
#y //it was grey.
Latitude
Strings are immutable in Latitude, so it is seldom necessary to explicitly copy one. However, a copy can be distinguished from the original using ===
a := "Hello".
b := a.
c := a clone.
println: a == b. ; True
println: a == c. ; True
println: a === b. ; True
println: a === c. ; False
LC3 Assembly
Copying a string is the same as copying any other zero-terminated array. This program copies the string at SRC to COPY, then prints the copy to show it has worked.
.ORIG 0x3000
LEA R1,SRC
LEA R2,COPY
LOOP LDR R3,R1,0
STR R3,R2,0
BRZ DONE
ADD R1,R1,1
ADD R2,R2,1
BRNZP LOOP
DONE LEA R0,COPY
PUTS
HALT
SRC .STRINGZ "What, has this thing appeared again tonight?"
COPY .BLKW 128
.END
- Output:
What, has this thing appeared again tonight?
LFE
(let* ((a '"data assigned to a")
(b a))
(: io format '"Contents of 'b': ~s~n" (list b)))
- Output:
Contents of 'b': data assigned to a
One can also use set
to copy a sting when one is in the LFE REPL:
> (set a '"data")
"data"
> a
"data"
> (set b a)
"data"
> b
"data"
Liberty BASIC
src$ = "Hello"
dest$ = src$
print src$
print dest$
Lingo
str = "Hello world!"
str2 = str
Syntax-wise strings are not immuatable in Lingo. You can alter an existing string without new assignment:
put "X" before str
put "X" after str
put "X" into char 6 of str
put str
-- "XHellX world!X"
But memory-wise they are immutable: Lingo internally stores references to strings, and as soon as a string is altered, a new copy is created on the fly, so other references to the original string are not affected by the change.
Lisaac
+ scon : STRING_CONSTANT;
+ svar : STRING;
scon := "sample";
svar := STRING.create 20;
svar.copy scon;
svar.append "!\n";
svar.print;
STRING_CONSTANT is immutable, STRING is not.
Little
string a = "A string";
string b = a;
a =~ s/$/\./;
puts(a);
puts(b);
LiveCode
put "foo" into bar
put bar into baz
answer bar && baz
Copies are nearly always made, on function calls parameters may be passed by reference (pointer) by prepending @ to a parameter in the function definition, however this is the only case where it is usually performed.
Logo
As a functional language, words are normally treated as symbols and cannot be modified. The EQUAL? predicate compares contents instead of identity. In UCB Logo the .EQ predicate tests for "thing" identity.
make "a "foo
make "b "foo
print .eq :a :b ; true, identical symbols are reused
make "c :a
print .eq :a :c ; true, copy a reference
make "c word :b "|| ; force a copy of the contents of a word by appending the empty word
print equal? :b :c ; true
print .eq :b :c ; false
Lua
Lua strings are immutable, so only one reference to each string exists.
a = "string"
b = a
print(a == b) -->true
print(b) -->string
Maple
In Maple, you cannot really copy a string in the sense that there can be two copies of the string in memory. As soon as you create a second copy of a string that already exists, it get turned into a reference to the first copy. However, you can copy a reference to a string by a simple assignment statement.
> s := "some string";
s := "some string"
> t := "some string";
t := "some string"
> evalb( s = t ); # they are equal
true
> addressof( s ) = addressof( t ); # not just equal data, but the same address in memory
3078334210 = 3078334210
> u := t: # copy reference
Mathematica / Wolfram Language
a="Hello World"
b=a
MATLAB
string1 = 'Hello';
string2 = string1;
Maxima
/* It's possible in Maxima to access individual characters by subscripts, but it's not the usual way.
Also, the result is "Lisp character", which cannot be used by other Maxima functions except cunlisp. The usual
way to access characters is charat, returning a "Maxima character" (actually a one characte string). With the latter,
it's impossible to modify a string in place, thus scopy is of little use. */
a: "loners"$
b: scopy(a)$
c: a$
c[2]: c[5]$
a;
"losers"
b;
"loners"
c;
"losers"
MAXScript
str1 = "Hello"
str2 = copy str1
Metafont
Metafont will always copy a string (does not make references).
string s, a;
s := "hello";
a := s;
s := s & " world";
message s; % writes "hello world"
message a; % writes "hello"
end
MiniScript
phrase = "hi"
copy = phrase
print phrase
print copy
MIPS Assembly
This does a full copy of the string, not just copying the pointer to the string's contents.
.data
.text
strcpy:
addi $sp, $sp, -4
sw $s0, 0($sp)
add $s0, $zero, $zero
L1:
add $t1, $s0, $a1
lb $t2, 0($t1)
add $t3, $s0, $a0
sb $t2, 0($t3)
beq $t2, $zero, L2
addi $s0, $s0, 1
j L1
L2:
lw $s0, 0($sp)
addi $sp, $sp, 4
jr $ra
Mirah
src = "Hello"
new_alias = src
puts 'interned strings are equal' if src == new_alias
str_copy = String.new(src)
puts 'non-interned strings are not equal' if str_copy != src
puts 'compare strings with equals()' if str_copy.equals(src)
Modula-3
Strings in Modula-3 have the type TEXT
.
VAR src: TEXT := "Foo";
VAR dst: TEXT := src;
MUMPS
SET S1="Greetings, Planet"
SET S2=S1
Nanoquery
a = "Hello"
b = a
Neko
var src = "Hello"
var dst = src
Nemerle
Nemerle gives you the option of declaring a variable - even a string - as mutable, so the caveats of languages with only immutable strings don't necessarily apply. However, Nemerle binds the value of the string to the new name when copying; to sort of emulate copying a reference you can use lazy evaluation.
using System;
using System.Console;
using Nemerle;
module StrCopy
{
Main() : void
{
mutable str1 = "I am not changed"; // str1 is bound to literal
def str2 = lazy(str1); // str2 will be bound when evaluated
def str3 = str1; // str3 is bound to value of str1
str1 = "I am changed"; // str1 is bound to new literal
Write($"$(str1)\n$(str2)\n$(str3)\n"); // str2 is bound to value of str1
// Output: I am changed
// I am changed
// I am not changed
}
}
NetRexx
In addition to the string capabilities provided by the Java String libraries (see Java for some examples) NetRexx provides comprehensive string capabilities through the built-in Rexx type. Rexx strings can be copied by simple assignment; as follows:
/* NetRexx */
options replace format comments java crossref symbols nobinary
s1 = 'This is a Rexx string'
s2 = s1
s2 = s2.changestr(' ', '_')
say s1
say s2
In this example a string is created, the string is copied then the copy is modified with the changestr built-in function. Finally both strings are displayed to confirm that the original string wasn't modified by the call to changestr.
- Output:
This is a Rexx string This_is_a_Rexx_string
NewLISP
(define (assert f msg) (if (not f) (println msg)))
(setq s "Greetings!" c (copy s))
(reverse c) ; Modifies c in place.
(assert (= s c) "Strings not equal.")
; another way
; Nehal-Singhal 2018-05-25
> (setq a "abcd")
"abcd"
> (setq b a)
"abcd"
> b
"abcd"
> (= a b)
true
Nim
var
c = "This is a string"
d = c # Copy c into a new string
NS-HUBASIC
10 A$ = "HELLO"
20 B$ = A$
30 A$ = "HI"
40 PRINT A$, B$
Oberon-2
MODULE CopyString;
TYPE
String = ARRAY 128 OF CHAR;
VAR
a,b: String;
BEGIN
a := "plain string";
COPY(a,b);
END CopyString.
Objeck
a := "GoodBye!";
b := a;
Objective-C
Immutable strings - since they are immutable, you may get the same instance with its references count increased. Or, you can get a copy which is mutable if you use mutableCopy
. Remember that both copy
and mutableCopy
return a retained instance. You can also get a copy by doing [NSString stringWithString:]
or [[NSString alloc] initWithString:]
.
Note that both copy
and initWithString:
/stringWithString:
are optimized to return the original string object (possibly retained) if it is immutable.
NSString *original = @"Literal String";
NSString *new = [original copy];
NSString *anotherNew = [NSString stringWithString:original];
NSString *newMutable = [original mutableCopy];
Mutable strings - you can get either new mutable (if you use mutableCopy
) or immutable (if you use copy
) string:
NSMutableString *original = [NSMutableString stringWithString:@"Literal String"];
NSString *immutable = [original copy];
NSString *anotherImmutable = [NSString stringWithString:original];
NSMutableString *mutable = [original mutableCopy];
Copying a CString into an NSString:
const char *cstring = "I'm a plain C string";
NSString *string = [NSString stringWithUTF8String:cstring];
Copying from data, possibly not null terminated:
char bytes[] = "some data";
NSString *string = [[NSString alloc] initWithBytes:bytes length:9 encoding:NSASCIIStringEncoding];
And of course, if a C string is needed, you can use standard functions like strcpy.
OCaml
let src = "foobar"
Before OCaml 4.02 (2014), strings were mutable and explicit deep copying was needed:
let dst = String.copy src
Between 4.02 and 4.06 (2017), immutable strings were optionally enabled via a flag: -safe-string
. A Bytes
module was added to provide safe and unsafe mutable views on strings. The two modules were synonymous unless the aforementioned flag was added.
(* Transition-period synonymy between types, explicit type annotations are just for emphasis *)
let dst1 : string = Bytes.copy (src : bytes)
let dst2 : bytes = Bytes.copy (src : string)
(* fails to compile with -safe-string *)
After 4.06, immutable strings became the default, Bytes
still exists, but its type is now distinct. The only way to get mutable strings and type synonymy back is at configure-time on the compiler itself.
String.copy
issues a deprecation warning, and a (shallow) copy would simply be an assignment by default:
let dst = src
To get a mutable deep-copy still, just convert the string to bytes via Bytes.of_string
, which copies for safety, or String.sub/map/init/..
for an immutable copy.
depending on your compiler version, choose the example accordingly.
Octave
str2 = str1
Oforth
To make a copy of the reference, just dup the string
"abcde" dup
There is no need to copy a string content as strings are immutable. If really needed :
StringBuffer new "abcde" <<
Ol
(define a "The String.")
; copy the string
(define b (runes->string (string->runes a)))
(print "a: " a)
(print "b: " b)
(print "b is an a: " (eq? a b))
(print "b same as a: " (equal? a b))
; another way: marshal the string
(define c (fasl-decode (fasl-encode a) #f))
(print "a: " a)
(print "c: " c)
(print "c is an a: " (eq? a c))
(print "c same as a: " (equal? a c))
- Output:
a: The String. b: The String. b is an a: #false b same as a: #true a: The String. c: The String. c is an a: #false c same as a: #true
ooRexx
/* Rexx ***************************************************************
* 16.05.2013 Walter Pachl
**********************************************************************/
s1 = 'This is a Rexx string'
s2 = s1 /* does not copy the string */
Say 's1='s1
Say 's2='s2
i1=s1~identityhash; Say 's1~identityhash='i1
i2=s2~identityhash; Say 's2~identityhash='i2
s2 = s2~changestr('*', '*') /* creates a modified copy */
Say 's1='s1
Say 's2='s2
i1=s1~identityhash; Say 's1~identityhash='i1
i2=s2~identityhash; Say 's2~identityhash='i2
- Output:
s1=This is a Rexx string s2=This is a Rexx string s1~identityhash=17587366586244 s2~identityhash=17587366586244 s1=This is a Rexx string s2=This is a Rexx string s1~identityhash=17587366586244 s2~identityhash=17587366588032
OxygenBasic
string s, t="hello"
s=t
PARI/GP
Assignment in GP always copies.
s1=s
In PARI, strings can be copied and references can be made.
GEN string_copy = gcopy(string);
GEN string_ref = string;
Pascal
See also: Delphi
program copyAString;
var
{ The Extended Pascal `string` schema data type
is essentially a `packed array[1..capacity] of char`. }
source, destination: string(80);
begin
source := 'Hello world!';
{ In Pascal _whole_ array data type values can be copied by assignment. }
destination := source;
{ Provided `source` is a _non-empty_ string value
you can copy in Extended Pascal sub-ranges _of_ _string_ types, too.
Note, the sub-range notation is not permitted for a `bindable` data type. }
destination := source[1..length(source)];
{ You can also employ Extended Pascal’s `writeStr` routine: }
writeStr(destination, source);
end.
Perl
To copy a string, just use ordinary assignment:
my $original = 'Hello.';
my $new = $original;
$new = 'Goodbye.';
print "$original\n"; # prints "Hello."
To create a reference to an existing string, so that modifying the referent changes the original string, use a backslash:
my $original = 'Hello.';
my $ref = \$original;
$$ref = 'Goodbye.';
print "$original\n"; # prints "Goodbye."
If you want a new name for the same string, so that you can modify it without dereferencing a reference, assign a reference to a typeglob:
my $original = 'Hello.';
our $alias;
local *alias = \$original;
$alias = 'Good evening.';
print "$original\n"; # prints "Good evening."
Note that our $alias, though in most cases a no-op, is necessary under stricture. Beware that local binds dynamically, so any subroutines called in this scope will see (and possibly modify!) the value of $alias assigned here.
To make a lexical variable that is an alias of some other variable, the Lexical::Alias module can be used:
use Lexical::Alias;
my $original = 'Hello.';
my $alias;
alias $alias, $original;
$alias = 'Good evening.';
print "$original\n"; # prints "Good evening."
Phix
Use of strings is utterly intuitive with no unexpected side effects. For example
string one = "feed" string two = one -- (two becomes "feed", one remains "feed") two[2..3] = "oo" -- (two becomes "food", one remains "feed") one[1] = 'n' -- (two remains "food", one becomes "need") ?{one,two}
- Output:
{"need","food"}
Phix variables are reference counted (except for integers). When a simple copy is made, it increases the reference count and shares the data, making it very fast on large sequences and long strings. Attempts to modify any data with a reference count greater than one cause a copy to be made, and all other variables are left unchanged. Strings can be modified "in situ", no problem.
PHP
$src = "Hello";
$dst = $src;
Picat
Use copy_term/1
to ensure that the original string is not changed.
go =>
S1 = "string",
println(s1=S1),
S2 = S1,
S2[1] := 'x', % also changes S1
println(s1=S1),
println(s2=S2),
nl,
S3 = "string",
S4 = copy_term(S3),
S4[1] := 'x', % no change of S3
println(s3=S3),
println(s4=S4),
nl.
- Output:
s1 = string s1 = xtring s2 = xtring s3 = string s4 = xtring
PicoLisp
(setq Str1 "abcdef")
(setq Str2 Str1) # Create a reference to that symbol
(setq Str3 (name Str1)) # Create new symbol with name "abcdef"
Pike
int main(){
string hi = "Hello World.";
string ih = hi;
}
PL/I
declare (s1, s2) character (20) varying;
s1 = 'now is the time';
s2 = s1;
Pop11
In Pop11 normal data are represented by references, so plain assignment will copy references. To copy data one has to use copy procedure:
vars src, dst;
'Hello' -> src;
copy(src) -> dst;
One can also combine assignment (initialization) with variable declarations:
vars src='Hello';
vars dst=copy(src);
PostScript
In PostScript,
(hello) dup length string copy
PowerShell
Since PowerShell uses .NET behind the scenes and .NET strings are immutable you can simply assign the same string to another variable without breaking anything:
$str = "foo"
$dup = $str
To actually create a copy the Clone()
method can be used:
$dup = $str.Clone()
ProDOS
editvar /newvar /value=a /userinput=1 /title=Enter a string to be copied:
editvar /newvar /value=b /userinput=1 /title=Enter current directory of the string:
editvar /newvar /value=c /userinput=1 /title=Enter file to copy to:
copy -a- from -b- to -c-
Prolog
Values in Prolog are immutable so unifying with a variable that already has the value of a string will effectively copy that string. You cannot reassign a value once it has been unified, it is not logical to have a value equal more than one thing.
?- A = "A test string", A = B.
A = B, B = "A test string".
PureBasic
src$ = "Hello"
dst$ = src$
Python
Since strings are immutable, all copy operations return the same string, with the reference count increased as appropriate
>>> src = "hello"
>>> a = src
>>> b = src[:]
>>> import copy
>>> c = copy.copy(src)
>>> d = copy.deepcopy(src)
>>> src is a is b is c is d
True
To actually copy a string:
>>> a = 'hello'
>>> b = ''.join(a)
>>> a == b
True
>>> b is a ### Might be True ... depends on "interning" implementation details!
False
As a result of object "interning" some strings such as the empty string and single character strings like 'a' may be references to the same object regardless of copying. This can potentially happen with any Python immutable object and should be of no consequence to any proper code.
Be careful with is - use it only when you want to compare the identity of the object. To compare string values, use the == operator. For numbers and strings any given Python interpreter's implementation of "interning" may cause the object identities to coincide. Thus any number of names to identical numbers or strings might become references to the same objects regardless of how those objects were derived (even if the contents were properly "copied" around). The fact that these are immutable objects makes this a reasonable behavior.
Quackery
Strings are immutable.
$ "hello" dup
R
Copy a string by value:
str1 <- "abc"
str2 <- str1
Racket
#lang racket
(let* ([s1 "Hey"]
[s2 s1]
[s3 (string-copy s1)]
[s4 s3])
(printf "s1 and s2 refer to ~a strings\n"
(if (eq? s1 s2) "the same" "different")) ; same
(printf "s1 and s3 refer to ~a strings\n"
(if (eq? s1 s3) "the same" "different")) ; different
(printf "s3 and s4 refer to ~a strings\n"
(if (eq? s3 s4) "the same" "different")) ; same
(string-fill! s3 #\!)
(printf "~a~a~a~a\n" s1 s2 s3 s4)) ; outputs "HeyHey!!!!!!"
Raku
(formerly Perl 6)
There is no special handling needed to copy a string; just assign it to a new variable:
my $original = 'Hello.';
my $copy = $original;
say $copy; # prints "Hello."
$copy = 'Goodbye.';
say $copy; # prints "Goodbye."
say $original; # prints "Hello."
You can also bind a new variable to an existing one so that each refers to, and can modify the same string.
my $original = 'Hello.';
my $bound := $original;
say $bound; # prints "Hello."
$bound = 'Goodbye.';
say $bound; # prints "Goodbye."
say $original; # prints "Goodbye."
Raven
Copy a string by reference:
'abc' as a
a as b
Copy a string by value:
'abc' as a
a copy as b
REBOL
REBOL [
Title: "String Copy"
URL: http://rosettacode.org/wiki/Copy_a_string
]
x: y: "Testing."
y/2: #"X"
print ["Both variables reference same string:" mold x "," mold y]
x: "Slackeriffic!"
print ["Now reference different strings:" mold x "," mold y]
y: copy x ; String copy here!
y/3: #"X" ; Modify string.
print ["x copied to y, then modified:" mold x "," mold y]
y: copy/part x 7 ; Copy only the first part of y to x.
print ["Partial copy:" mold x "," mold y]
y: copy/part skip x 2 3
print ["Partial copy from offset:" mold x "," mold y]
- Output:
Script: "String Copy" (16-Dec-2009) Both variables reference same string: "TXsting." , "TXsting." Now reference different strings: "Slackeriffic!" , "TXsting." x copied to y, then modified: "Slackeriffic!" , "SlXckeriffic!" Partial copy: "Slackeriffic!" , "Slacker" Partial copy from offset: "Slackeriffic!" , "ack"
Red
Red[]
originalString: "hello wordl"
copiedString: originalString
; OR
copiedString2: copy originalString
Retro
'this_is_a_string dup s:temp
REXX
The example shows how to copy the contents of one string into another string.
Note that delimiters for literal strings, REXX accepts either of:
- ' (an apostrophe)
- " (a double quote)
Also note that all REXX values (variables) are stored as (varying length) character strings.
src = "this is a string"
dst = src
Ring
cStr1 = "Hello!" # create original string
cStr2 = cStr1 # make new string from original
RLaB
>> s1 = "A string"
A string
>> s2 = s1
A string
Robotic
set "$string1" to "This is a string"
set "$string2" to "$string1"
* "&$string2&"
RPL
Copy a string in stack:
DUP
Copy a string from one variable to another:
"Example" 'STR1' STO STR1 'STR2' STO
Ruby
In Ruby, String are mutable.
original = "hello"
reference = original # copies reference
copy1 = original.dup # instance of original.class
copy2 = String.new(original) # instance of String
original << " world!" # append
p reference #=> "hello world!"
p copy1 #=> "hello"
p copy2 #=> "hello"
There is a method of Object#clone, too, in the copy of the object.
original = "hello".freeze # prevents further modifications
copy1 = original.dup # copies contents (without status)
copy2 = original.clone # copies contents (with status)
p copy1.frozen? #=> false
p copy1 << " world!" #=> "hello world!"
p copy2.frozen? #=> true
p copy2 << " world!" #=> can't modify frozen String (RuntimeError)
Run BASIC
origString$ = "Hello!" ' create original string
newString$ = origString$ ' make new strig from original
Rust
fn main() {
let s1 = "A String";
let mut s2 = s1;
s2 = "Another String";
println!("s1 = {}, s2 = {}", s1, s2);
}
Output:
s1 = A String, s2 = Another String
Sather
class MAIN is
main is
s ::= "a string";
s1 ::= s;
-- s1 is a copy
end;
end;
Scala
val src = "Hello"
// Its actually not a copy but a reference
// That is not a problem because String is immutable
// In fact its a feature
val des = src
assert(src eq des) // Proves the same reference is used.
// To make a real copy makes no sense.
// Actually its hard to make a copy, the compiler is too smart.
// mkString, toString makes also not a real copy
val cop = src.mkString.toString
assert((src eq cop)) // Still no copyed image
val copy = src.reverse.reverse // Finally double reverse makes a copy
assert(src == copy && !(src eq copy))// Prove, but it really makes no sense.
Scheme
(define dst (string-copy src))
sed
In sed, there are two distinct locations for storing a string: The "pattern space" and the "hold space". The h
command copies pattern space to hold space. The g
command copies hold space to pattern space.
Seed7
var string: dest is "";
dest := "Hello";
SenseTalk
(* In SenseTalk, assignments normally always make copies of values. *)
put "glorious" into myWord
put myWord into yourWord
(* Assignments can also be made by reference if desired. *)
put a reference to myWord into myRef
set another to refer to myRef
put "ly" after myWord
put "in" before another
put "myWord: " & myWord
put "yourWord: " & yourWord
put "myRef: " & myRef
put "another: " & another
- Output:
myWord: ingloriously yourWord: glorious myRef: ingloriously another: ingloriously
Shiny
src: 'hello'
cpy: src
Sidef
var original = "hello"; # new String object
var reference = original; # points at the original object
var copy1 = String.new(original); # creates a new String object
var copy2 = original+''; # ==//==
Simula
BEGIN
TEXT ORIGINAL, REFERENCE, COPY1;
ORIGINAL :- "THIS IS CONSTANT TEXT";
ORIGINAL.SETPOS(1);
REFERENCE :- ORIGINAL;
! RUN TIME ERROR:
! ORIGINAL.PUTCHAR('X');
! "copy-a-string.sim", line 9: ./copy-a-string: Putchar: Constant text object
;
OUTTEXT(ORIGINAL);
OUTIMAGE;
! CONTENT EQUAL? => T ;
OUTTEXT(IF ORIGINAL = REFERENCE THEN "T" ELSE "F");
OUTIMAGE;
! SAME TEXT OBJECT? => T ;
OUTTEXT(IF ORIGINAL == REFERENCE THEN "T" ELSE "F");
OUTIMAGE;
COPY1 :- COPY(ORIGINAL);
COPY1.SETPOS(1);
COPY1.PUTCHAR('X');
OUTTEXT(COPY1);
OUTIMAGE;
END;
- Output:
THIS IS CONSTANT TEXT T T XHIS IS CONSTANT TEXT
Slate
[ | :s | s == s copy] applyTo: {'hello'}. "returns False"
Smalltalk
|s1 s2|
"bind the var s1 to the object string on the right"
s1 := 'i am a string'.
"bind the var s2 to the same object..."
s2 := s1.
"bind s2 to a copy of the object bound to s1"
s2 := (s1 copy).
SNOBOL4
* copy a to b
b = a = "test"
output = a
output = b
* change the copy
b "t" = "T"
output = b
end
- Output:
test test Test
Standard ML
In Standard ML, string
s are immutable, so you don't copy it.
Instead, maybe you want to create a CharArray.array
(mutable string) from an existing string
:
val src = "Hello";
val srcCopy = CharArray.array (size src, #"x"); (* 'x' is just dummy character *)
CharArray.copyVec {src = src, dst = srcCopy, di = 0};
src = CharArray.vector srcCopy; (* evaluates to true *)
or from another CharArray.array
:
val srcCopy2 = CharArray.array (CharArray.length srcCopy, #"x"); (* 'x' is just dummy character *)
CharArray.copy {src = srcCopy, dst = srcCopy2, di = 0};
Swift
Just use assignment:
var src = "Hello"
var dst = src
Strings in Swift are value types, so assigning copies the string.
Tcl
set src "Rosetta Code"
set dst $src
Tcl copies strings internally when needed. To be exact, it uses a basic value model based on simple objects that are immutable when shared (i.e., when they have more than one effective reference to them); when unshared, they can be changed because the only holder of a reference has to be the code requesting the change. At the script level, this looks like Tcl is making a copy when the variable is assigned as above, but is more efficient in the common case where a value is not actually modified.
TI-83 BASIC
:"Rosetta Code"→Str1
:Str1→Str2
TI-89 BASIC
:"Rosetta Code"→str1
:str1→str2
Toka
" hello" is-data a
a string.clone is-data b
Transd
#lang transd
MainModule : {
_start: (λ
(with s "Hello!" s1 "" s2 ""
(= s1 s) // duplication of 's' content
(rebind s2 s) // another reference to 's'
(= s "Good bye!")
(lout s)
(lout s1)
(lout s2)
)
)
}
- Output:
Good bye! Hello! Good bye!
Trith
Strings are immutable character sequences, so copying a string just means duplicating the reference at the top of the stack:
"Hello" dup
TUSCRIPT
$$ MODE TUSCRIPT
str="Hello"
dst=str
UNIX Shell
foo="Hello"
bar=$foo # This is a copy of the string
Ursa
decl string a b
set a "hello"
set b a
V
dup really makes a reference, but the language is functional, so the string is immutable.
"hello" dup
VBA
This program copies string in variable a to variable b. Mutating variable a subsequently doesn't alter variable b. Variable b is not a reference.
Sub copystring()
a = "Hello World!"
b = a
a = "I'm gone"
Debug.Print b
Debug.Print a
End Sub
- Output:
Hello World! I'm gone
Vim Script
let str1 = "original string"
let str2 = str1
let str1 = "new string"
echo "String 1:" str1
echo "String 2:" str2
- Output:
String 1: new string String 2: original string
Visual Basic .NET
Platform: .NET
'Immutable Strings
Dim a = "Test string"
Dim b = a 'reference to same string
Dim c = New String(a.ToCharArray) 'new string, normally not used
'Mutable Strings
Dim x As New Text.StringBuilder("Test string")
Dim y = x 'reference
Dim z = New Text.StringBuilder(x.ToString) 'new string
Alternatively, you can use, with all versions of the .NET framework:
Dim a As String = "Test String"
Dim b As String = String.Copy(a) ' New string
V (Vlang)
Strings in Vlang are immutable. There is no need to distinguish between copying and making an additional reference.
text := "Hello"
copy_of := text
println(copy_of)
- Output:
Hello
Wren
A string in Wren is an immutable array of bytes.
Although technically a reference type, this means there is no need to distinguish between copying the contents of a string and making an additional reference. We can therefore just use assignment to copy a string.
var s = "wren"
var t = s
System.print("Are 's' and 't' equal? %(s == t)")
- Output:
Are 's' and 't' equal? true
X86 Assembly
creating a second 0 terminated string with the same content:
section .data
string db "Hello World", 0
section .bss
string2 resb 12
section .text
global _main
_main:
mov ecx, 0
looping:
mov al, [string + ecx]
mov [string2 + ecx], al
inc ecx
cmp al, 0 ;copy until we find the terminating 0
je end
jmp looping
end:
xor eax, eax
ret
creating a second string; first byte signals length of string
section .data
string db 11,"Hello World"
section .bss
string2 resb 12
section .text
global _main
_main:
xor ecx, ecx ;clear ecx
mov cl, [string]
mov [string2], cl ;copy byte signaling length
mov edx, 1
looping: ;copy each single byte
mov al, [string + edx]
mov [string2 + edx], al
inc edx
dec ecx
cmp ecx, 0
jg looping
xor eax, eax
ret
X86-64 Assembly
UASM 2.52
option casemap:none
option literals:on
printf proto :dword, :VARARG
exit proto :dword
.data
s db "Goodbye, World!",0
.data?
d db 20 dup (?)
dp dq ?
tb dd ?
.code
main proc
lea rsi, s ;; Put the address of var S into the source index(RSI)
xor rcx, rcx ;; Zero out RCX
_getsize:
inc rcx ;; Advanced the index by 1
cmp byte ptr [rsi+rcx],0 ;; check the current byte for terminating 0
jne _getsize ;; nope, jump back and check again
mov tb, ecx ;; tb = Total bytes, Keep a copy of the size of the string
lea rsi, s ;; Copy the address of s into the source index(rsi)
lea rdi, d ;; Copy the address of d into the destination index(rdi)
rep movsb ;; Copy bytes from ESI to EDI until RCX is 0
lea rax, s ;; Get the address of S
mov dp, rax ;; Copy it from RAX to dp
mov rbx,rdi ;; Make a copy of RDI, cause over writes due to ABI call args T_T
invoke printf, CSTR("-> s (0x%x) = %s",10), rsi, addr s
invoke printf, CSTR("-> d (0x%x) = %s",10), rbx, addr d
invoke printf, CSTR("-> dp (0x%x) = %s",10), addr dp, dp
invoke printf, CSTR("-> bytes copied: %i",10), tb
xor rsi, rsi
call exit
ret
main endp
end
- Output:
-> s (0x40303f) = Goodbye, World! -> d (0x40309f) = Goodbye, World! -> dp (0x4030a4) = Goodbye, World! -> bytes copied: 15
NASM 2.15
%macro sysdef 2
%define sys_%1 %2
%endmacro
sysdef write, 1
%macro prolog 1
push rbp
mov rbp, rsp
sub rsp, %1
%endmacro
%macro epilog 1
add rsp, %1
pop rbp
%endmacro
%macro xlea 2
lea %1, [rel %2]
%endmacro
%macro inv 1-7 0,0,0,0,0,0
mov r9,%7
mov r8,%6
mov r10,%5
mov rdx,%4
mov rsi,%3
mov rdi,%2
mov rax,sys_%1
syscall
%endmacro
section .rodata
sz1 db "Goodbye, World!",0xa,0
section .bss
sz2 resq 1
section .text
strlcpy:
prolog 0x38
%define dest rbp-0x18
%define src rbp-0x10
%define n rbp-0x8
mov qword [rbp-0x28], rdi
mov qword [rbp-0x30], rsi
mov qword [rbp-0x38], rdx
mov rax, qword [rbp-0x28]
mov qword [dest], rax
mov rax, qword [rbp-0x30]
mov qword [src], rax
mov rax, qword [rbp-0x38]
mov qword [n], rax
cmp qword [n], 0
je _stlc_done
_stlc_doloop:
dec qword [n]
cmp qword [n], 0
je _stlc_done
mov rbx, qword [src]
lea rax, [rbx+1]
mov qword [src], rax
mov rax, qword [dest]
lea rcx, [rax+1]
mov qword [dest], rcx
movzx ebx, byte [rbx]
mov byte [rax], bl
movzx eax, byte [rax]
test al, al
je _stlc_done
jmp _stlc_doloop
_stlc_done:
epilog 0x38
ret
strlen:
prolog 0x10
%define s rbp-0x8
mov qword [rbp-0x10], rdi
mov rax, qword [rbp-0x10]
mov qword [s], rax
mov rsi, qword [s]
xor rcx, rcx
_stl_count:
cmp byte [rsi+rcx], 0
je _stl_exit
inc rcx
jne _stl_count
_stl_exit:
mov rax, rcx
epilog 0x10
ret
global main
main:
prolog 0x20
%define tmp rbp-0x20
xlea rbx, sz1
mov qword [tmp], rbx
mov rdi, qword [tmp]
call strlen
mov rcx, rax
push rcx
mov rdx, rcx
xlea rsi, sz1
xlea rdi, sz2
call strlcpy
xlea rbx, sz2
pop rcx
inv write, 1, rbx, rcx
inv exit, 0
epilog 0x20
ret
- Output:
Goodbye, World!
XPL0
The default method of terminating strings is to set the most significant bit of the last character. An alternative is to use the 'string 0' command to specify zero-terminated strings. The string copy routine from the standard library is shown.
proc StrCopy(A, B); \Copy string: A --> B
char A, B; \Strings: B must already have enough space "Reserved"
int I; \Beware if strings overlap
for I:= 0 to -1>>1-1 do
[B(I):= A(I);
if A(I) >= $80 then return
];
char S1, S2, S3(13);
[S1:= "Hello, world!"; \S1 now points to the string
S2:= S1; \S2 now also points to the string
StrCopy(S1, S3); \S3 points to a separate copy of the string
]
Z80 Assembly
Making An Additional Reference
Making an additional reference to a string is easy. If you know the address of the beginning of the string, store that address in RAM somewhere else.
ld hl,MyString
ld (PointerVariable),hl
MyString: ;assembler equates this label to a memory location at compile time
byte "Hello",0
PointerVariable:
word 0 ;placeholder for the address of the above string, gets written to by the code above.
NOTE: If you're programming for the Game Boy, you can't store a 16-bit value directly into RAM from HL
. There are other methods to achieve the same result, and here's one:
ld a,<MyString ; < represents the low byte of the address. Some assemblers use LOW() with the label in the parentheses.
ld (PointerVariable),a
ld a,>MyString ; > represents the high byte of the address. Some assemblers use HIGH() with the label in the parentheses.
ld (PointerVariable+1),a
Copying A String
As long as you have enough RAM space to hold the entire string, you can copy it somewhere else in memory. If you know the string's length in advance a simple LDIR
will be sufficient. This method will use the null terminator to tell the copy function when to stop:
StrCpy:
;input: HL = base address of string you wish to copy
; DE = where you want to copy it to.
; This program assumes that the string is null-terminated, and that there is enough RAM to hold the entire string.
ld a,(hl)
or a ;compare A to 0.
ret z
ld (de),a
inc hl
inc de
jr StrCpy
If you're using the "Pascal style" where the string length is prepended before the string itself, you can use this method instead, assuming your string is shorter than 255 bytes in length.
ld hl,myString
ld c,(hl)
ld b,0
inc c
ld de,buffer
ldir ;copies from (HL) to (DE), BC times.
ret
myString:
byte 5 ;len("Hello")
byte "Hello"
buffer:
byte 0
byte 0,0,0,0,0
Zig
const std = @import("std");
const debug = std.debug;
const mem = std.mem;
test "copy a string" {
const source = "A string.";
// Variable `dest1` will have the same type as `source`, which is
// `*const [9:0]u8`.
const dest1 = source;
// Variable `dest2`'s type is [9]u8.
//
// The difference between the two is that `dest1` string is null-terminated,
// while `dest2` is not.
var dest2: [source.len]u8 = undefined;
mem.copy(u8, dest2[0..], source[0..]);
debug.assert(mem.eql(u8, dest1[0..], "A string."));
debug.assert(mem.eql(u8, dest2[0..], "A string."));
}
zkl
Strings are immutable so copy is just return the string:
"abc".copy() // noop
zonnon
module Main;
var
s,r: string;
c: array 60 of char;
begin
s := "plain string";r := s; writeln(s);
(* copy string to array of char *)
copy(s,c);c[0] := 'P';
(* copy array of char to string *)
copy(c,r);writeln(r);
end Main.
Zoomscript
For typing:
var a
var b
a = "World"
b = a
a = "Hello"
print (a," ",b)
For importing:
¶0¶var a¶0¶var b¶0¶a = "World"¶0¶b = a¶0¶a = "Hello"¶0¶print (a," ",b)
ZX Spectrum Basic
10 LET a$ = "Hello": REM a$ is the original string
20 LET b$ = a$: REM b$ is the copy
Amazing Hopper
Version 1: Assign variable "s" to variable "b".
#include <hopper.h>
main:
s = "string to copy"
t = s
{s,"\n",t}println
exit(0)
Output:
string to copy string to copy
Version 2: Soft copy to variable (CPY).
#include <hopper.h>
main:
s=""
{"1:","string to copy"},cpy(s),println
{"2:",s}println
exit(0)
Output:
1:string to copy 2:string to copy
Version 3: From stack to var: hard copy (move, MOV).
#include <hopper.h>
main:
s=""
{"string to copy"},mov(s)
{s}println
exit(0)
Output:
string to copy
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