Split a character string based on change of character: Difference between revisions

From Rosetta Code
No edit summary
Line 2,598: Line 2,598:
   
 
<pre>g, HHH, 5, YY, ++, ///, \</pre>
 
<pre>g, HHH, 5, YY, ++, ///, \</pre>
  +
  +
=={{header|Transd}}==
  +
The task doesn't state explicitly about the order in which substrings should be
  +
displayed. So, here are two variants: one is order-preserving, the other is not
  +
order-preserving.
  +
<syntaxhighlight lang="Scheme">#lang transd
  +
  +
MainModule: {
  +
s: "gHHH5YY++///\\",
  +
_start: (λ
  +
(with res ""
  +
(for c in (split s "") do
  +
(if (neq Char(c) (back res)) (+= res ", "))
  +
(+= res c))
  +
(textout res))
  +
  +
(lout "Second variant: ")
  +
  +
(for v in (values (group-by (split s ""))) do
  +
(textout (if @idx ", ") (join v "")))
  +
)
  +
}</syntaxhighlight>
  +
{{out}}
  +
<pre>
  +
g, HHH, 5, YY, ++, ///, \
  +
Second variant:
  +
++, ///, 5, HHH, YY, \, g
  +
</pre>
   
 
=={{header|VBA}}==
 
=={{header|VBA}}==

Revision as of 16:14, 24 September 2022

Task
Split a character string based on change of character
You are encouraged to solve this task according to the task description, using any language you may know.


Task

Split a (character) string into comma (plus a blank) delimited strings based on a change of character   (left to right).

Show the output here   (use the 1st example below).


Blanks should be treated as any other character   (except they are problematic to display clearly).   The same applies to commas.


For instance, the string:

 gHHH5YY++///\ 

should be split and show:

 g, HHH, 5, YY, ++, ///, \ 


Other tasks related to string operations:
Metrics
Counting
Remove/replace
Anagrams/Derangements/shuffling
Find/Search/Determine
Formatting
Song lyrics/poems/Mad Libs/phrases
Tokenize
Sequences



11l

Translation of: C++
F split(input, delim)
   V res = ‘’
   L(ch) input
      I !res.empty & ch != res.last
         res ‘’= delim
      res ‘’= ch
   R res

print(split(‘gHHH5YY++///\’, ‘, ’))
Output:
g, HHH, 5, YY, ++, ///, \

8080 Assembly

	org	100h
	jmp	demo
	;;;	Split the string under DE on changing characters,
	;;;	and store the result at HL.
split:	ldax	d	; Load character from string
spcopy:	mov	m,a	; Store in output
	cpi	'$'	; CP/M string terminator
	rz		; Stop when the end is reached
	mov	b,a	; Store previous character in B
	inx	d	; Increment input pointer
	inx	h	; Increment output pointer
	ldax	d	; Get next character
	cmp	b	; Same as previous character?
	jz	spcopy	; Then just copy it
	cpi	'$'	; Otherwise, if it is the en 
	jz	spcopy	; Then just copy it as well
	mvi	m,','	; Otherwise, add a comma and a space
	inx	h
	mvi	m,' '
	inx	h
	jmp	spcopy
	;;;	Demo code
demo:	lxi	d,string
	lxi	h,out
	call	split	; Split the string
	lxi	d,out
	mvi	c,9	; And print it using CP/M
	jmp	5
string:	db	'gHHH5YY++///',5Ch,'$'
out:	equ	$
Output:
g, HHH, 5, YY, ++, ///, \

8086 Assembly

	cpu	8086
	org	100h
section	.text
	jmp	demo
	;;;	Split the string at DS:SI on changing characters,
	;;;	and store the result at ES:DI.
split:	lodsb		; Load character	
.copy:	stosb		; Store in output
	cmp	al,'$'	; Done yet?
	je	.out	; If so, stop.
	mov	ah,al	; Store previous character
	lodsb		; Get next character
	cmp	al,ah	; Same character?
	je	.copy	; Then just copy it
	cmp	al,'$'	; End of string?
	je	.copy	; Then just copy it too
	mov	dl,al
	mov	ax,', '	; Otherwise, add a comma and a space
	stosw
	mov	al,dl
	jmp	.copy
.out:	ret
	;;;	Demo code
demo:	mov	si,string
	mov	di,buf
	call	split	; Split the string
	mov	dx,buf
	mov	ah,9
	int	21h	; And print the result using DOS
	ret
section	.data
string:	db	'gHHH5YY++///\$'
section	.bss
buf:	resb	32
Output:
g, HHH, 5, YY, ++, ///, \

AArch64 Assembly

Works with: as version Raspberry Pi 3B version Buster 64 bits
/* ARM assembly AARCH64 Raspberry PI 3B */
/*  program splitcar64.s   */

/*******************************************/
/* Constantes file                         */
/*******************************************/
/* for this file see task include a file in language AArch64 assembly*/
.include "../includeConstantesARM64.inc"
 
/*********************************/
/* Initialized data              */
/*********************************/
.data
szCarriageReturn:   .asciz "\n"
szString1:          .asciz "gHHH5YY++///\\"
/*   IMPORTANT REMARK for compiler as 
The way to get special characters into a string is to escape these characters: precede them
with a backslash ‘\’ character. For example ‘\\’ represents one backslash: the first \ is
an escape which tells as to interpret the second character literally as a backslash (which
prevents as from recognizing the second \ as an escape character).
*/
 
/*********************************/
/* UnInitialized data            */
/*********************************/
.bss  
sBuffer:               .skip  100
 
/*********************************/
/*  code section                 */
/*********************************/
.text
.global main 
main:                              // entry of program 
 
    ldr x0,qAdrszString1           // input string address
    ldr x1,qAdrsBuffer             // output buffer address
    bl split 
 
    ldr x0,qAdrsBuffer
    bl affichageMess               // display message
    ldr x0,qAdrszCarriageReturn
    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
 
qAdrszString1:            .quad szString1
qAdrszCarriageReturn:     .quad szCarriageReturn
qAdrsBuffer:              .quad sBuffer
 
/******************************************************************/
/*     generate value                                  */ 
/******************************************************************/
/* x0 contains the address of input string  */
/* x1 contains the address of output buffer  */
 
split:
    stp x1,lr,[sp,-16]!            // save  registers
    mov x4,0                       // indice loop input string
    mov x5,0                       // indice buffer
    ldrb w2,[x0,x4]                // read first char in reg x2
    cbz x2,4f                       // if null -> end
    strb w2,[x1,x5]                // store char in buffer
    add x5,x5,1                    // increment location buffer
1:
    ldrb w3,[x0,x4]                //read char[x4] in reg x3
    cbz x3,4f                      // if null  end
    cmp x2,x3                      // compare two characters
    bne 2f
    strb w3,[x1,x5]                // = -> store char in buffer   
    b 3f                           // loop
2:
    mov x2,','                    // else store comma in buffer
    strb w2,[x1,x5]                // store char in buffer
    add x5,x5,1
    mov x2,' '                    // and store space in buffer
    strb w2,[x1,x5]
    add x5,x5,1
    strb w3,[x1,x5]               // and store input char in buffer
    mov x2,x3                     // and maj x2 with new char
3:
    add x5,x5,1                   // increment indices
    add x4,x4,1
    b 1b                          // and loop
4:
    strb w3,[x1,x5]               // store zero final in buffer
100:
    ldp x1,lr,[sp],16             // restaur  2 registers
    ret                           // return to address lr x30
/********************************************************/
/*        File Include fonctions                        */
/********************************************************/
/* for this file see task include a file in language AArch64 assembly */
.include "../includeARM64.inc"
Output:
 gg, HHH, 5, YY, ++, ///, \ 

Action!

PROC Split(CHAR ARRAY s)
  BYTE i
  CHAR curr,last

  i=1 last=s(1)
  Put('")
  WHILE i<=s(0)
  DO
    curr=s(i)
    IF curr#last THEN
      Print(", ")
    FI
    Put(curr)
    last=curr
    i==+1
  OD
  Put('")
RETURN

PROC Test(CHAR ARRAY s)
  PrintF("Input: ""%S""%E",s)
  Print("Split: ") Split(s)
  PutE() PutE()
RETURN

PROC Main()
  Test("gHHH5YY++///\")
  Test("gHHH   5++,,,///\")
RETURN
Output:

Screenshot from Atari 8-bit computer

Input: "gHHH5YY++///\"
Split: "g, HHH, 5, YY, ++, ///, \"

Input: "gHHH   5++,,,///\"
Split: "g, HHH,    , 5, ++, ,,,, ///, \"

Ada

with Ada.Text_IO;
procedure Split is 
  procedure Print_Tokens (s : String) is
    i, j : Integer := s'First;
  begin
    loop
      while j<=s'Last and then s(j)=s(i) loop j := j + 1; end loop;
      if i/=s'first then Ada.Text_IO.Put (", "); end if;
      Ada.Text_IO.Put (s(i..j-1));
      i := j;
      exit when j>s'last;
    end loop;
  end Print_Tokens;
begin
  Print_Tokens ("gHHH5YY+++");
end split;

ALGOL 68

Works with: ALGOL 68G version Any - tested with release 2.8.3.win32
BEGIN
    # returns s with ", " added between each change of character #
    PROC split on characters = ( STRING s )STRING:
         IF s = "" THEN
            # empty string #
            ""
         ELSE
            # allow for 3 times as many characters as in the string #
            # this would handle a string of unique characters       #
            [ 3 * ( ( UPB s - LWB s ) + 1 ) ]CHAR result;
            INT  r pos  := LWB result;
            INT  s pos  := LWB s;
            CHAR s char := s[ LWB s ];
            FOR s pos FROM LWB s TO UPB s DO
                IF s char /= s[ s pos ] THEN
                    # change of character - insert ", " #
                    result[ r pos     ] := ",";
                    result[ r pos + 1 ] := " ";
                    r pos +:= 2;
                    s char := s[ s pos ]
                FI;
                result[ r pos ] := s[ s pos ];
                r pos +:= 1
            OD;
            # return the used portion of the result #
            result[ 1 : r pos - 1 ]
         FI ; # split on characters #

    print( ( split on characters( "gHHH5YY++///\" ), newline ) )
END
Output:
g, HHH, 5, YY, ++, ///, \

ANSI BASIC

REM >split
DECLARE EXTERNAL FUNCTION FN_split$

PRINT FN_split$( "gHHH5YY++///\" )
END

EXTERNAL FUNCTION FN_split$( s$ )
LET c$ = s$(1:1)
LET split$ = ""
FOR i = 1 TO LEN(s$)
  LET d$ = s$(i:i)
  IF d$ <> c$ THEN
    LET split$ = split$ & ", "
    LET c$ = d$
  END IF
  LET split$ = split$ & d$
NEXT i
LET FN_split$ = split$
END FUNCTION
Output:
g, HHH, 5, YY, ++, ///, \

APL

Works with: Dyalog APL
split  2(', '),¨(⊢≠¯1⌽⊢)⊂⊢
Output:
      split 'gHHH5YY++///\'
g, HHH, 5, YY, ++, ///, \

AppleScript

Functional

Translation of: JavaScript
intercalate(", ", ¬
    map(curry(intercalate)'s |λ|(""), ¬
        group("gHHH5YY++///\\")))

--> "g, HHH, 5, YY, ++, ///, \\"


-- GENERIC FUNCTIONS ----------------------------------------------------------
-- curry :: (Script|Handler) -> Script
on curry(f)
    script
        on |λ|(a)
            script
                on |λ|(b)
                    |λ|(a, b) of mReturn(f)
                end |λ|
            end script
        end |λ|
    end script
end curry

-- foldl :: (a -> b -> a) -> a -> [b] -> a
on foldl(f, startValue, xs)
    tell mReturn(f)
        set v to startValue
        set lng to length of xs
        repeat with i from 1 to lng
            set v to |λ|(v, item i of xs, i, xs)
        end repeat
        return v
    end tell
end foldl

-- group :: Eq a => [a] -> [[a]]
on group(xs)
    script eq
        on |λ|(a, b)
            a = b
        end |λ|
    end script
    
    groupBy(eq, xs)
end group

-- groupBy :: (a -> a -> Bool) -> [a] -> [[a]]
on groupBy(f, xs)
    set mf to mReturn(f)
    
    script enGroup
        on |λ|(a, x)
            if length of (active of a) > 0 then
                set h to item 1 of active of a
            else
                set h to missing value
            end if
            
            if h is not missing value and mf's |λ|(h, x) then
                {active:(active of a) & x, sofar:sofar of a}
            else
                {active:{x}, sofar:(sofar of a) & {active of a}}
            end if
        end |λ|
    end script
    
    if length of xs > 0 then
        tell foldl(enGroup, {active:{item 1 of xs}, sofar:{}}, tail(xs))
            if length of (its active) > 0 then
                its sofar & its active
            else
                {}
            end if
        end tell
    else
        {}
    end if
end groupBy

-- intercalate :: Text -> [Text] -> Text
on intercalate(strText, lstText)
    set {dlm, my text item delimiters} to {my text item delimiters, strText}
    set strJoined to lstText as text
    set my text item delimiters to dlm
    return strJoined
end intercalate

-- map :: (a -> b) -> [a] -> [b]
on map(f, xs)
    tell mReturn(f)
        set lng to length of xs
        set lst to {}
        repeat with i from 1 to lng
            set end of lst to |λ|(item i of xs, i, xs)
        end repeat
        return lst
    end tell
end map

-- Lift 2nd class handler function into 1st class script wrapper 
-- mReturn :: Handler -> Script
on mReturn(f)
    if class of f is script then
        f
    else
        script
            property |λ| : f
        end script
    end if
end mReturn

-- tail :: [a] -> [a]
on tail(xs)
    if length of xs > 1 then
        items 2 thru -1 of xs
    else
        {}
    end if
end tail
Output:
g, HHH, 5, YY, ++, ///, \

Straightforward

(Also case-sensitve.)

on splitAtCharacterChanges(input)
    set len to (count input)
    if (len < 2) then return input
    set chrs to input's characters
    set currentChr to beginning of chrs
    considering case
        repeat with i from 2 to len
            set thisChr to item i of chrs
            if (thisChr is not currentChr) then
                set item i of chrs to ", " & thisChr
                set currentChr to thisChr
            end if
        end repeat
    end considering
    set astid to AppleScript's text item delimiters
    set AppleScript's text item delimiters to ""
    set output to chrs as text
    set AppleScript's text item delimiters to astid
    
    return output
end splitAtCharacterChanges

-- Test code:
splitAtCharacterChanges("gHHH5YY++///\\")
Output:
"g, HHH, 5, YY, ++, ///, \\"

ASObjC

use AppleScript version "2.4" -- OS X 10.10 (Yosemite) or later
use framework "Foundation"

on splitAtCharacterChanges(input)
    tell (current application's class "NSMutableString"'s stringWithString:(input)) to ¬
        return (its stringByReplacingOccurrencesOfString:("(.)\\1*+(?!$)") withString:("$0, ") ¬
            options:(current application's NSRegularExpressionSearch) range:({0, its |length|()})) as text
end splitAtCharacterChanges

-- Test code:
splitAtCharacterChanges("gHHH5YY++///\\")
Output:
"g, HHH, 5, YY, ++, ///, \\"

ARM Assembly

Works with: as version Raspberry Pi
/* ARM assembly Raspberry PI  */
/*  program splitcar.s   */
 
/************************************/
/* Constantes                       */
/************************************/
.equ STDOUT, 1     @ Linux output console
.equ EXIT,   1     @ Linux syscall
.equ WRITE,  4     @ Linux syscall

/*********************************/
/* Initialized data              */
/*********************************/
.data
szCarriageReturn:   .asciz "\n"
szString1:          .asciz "gHHH5YY++///\\"
/*   IMPORTANT REMARK for compiler as 
The way to get special characters into a string is to escape these characters: precede them
with a backslash ‘\’ character. For example ‘\\’ represents one backslash: the first \ is
an escape which tells as to interpret the second character literally as a backslash (which
prevents as from recognizing the second \ as an escape character).
*/

/*********************************/
/* UnInitialized data            */
/*********************************/
.bss  
sBuffer:               .skip  100

/*********************************/
/*  code section                 */
/*********************************/
.text
.global main 
main:                                             @ entry of program 

    ldr r0,iAdrszString1                          @ input string address
    ldr r1,iAdrsBuffer                            @ output buffer address
    bl split 

    ldr r0,iAdrsBuffer
    bl affichageMess                              @ display message
    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 the system call
 
iAdrszString1:            .int szString1
iAdrszCarriageReturn:     .int szCarriageReturn
iAdrsBuffer:              .int sBuffer

/******************************************************************/
/*     generate value                                  */ 
/******************************************************************/
/* r0 contains the address of input string  */
/* r1 contains the address of output buffer  */

split:
    push {r1-r5,lr}                           @ save registers
    mov r4,#0                                 @ indice loop input string
    mov r5,#0                                 @ indice buffer
    ldrb r2,[r0,r4]                           @ read first char in reg r2
    cmp r2,#0                                 @ if null -> end
    beq 3f
    strb r2,[r1,r5]                           @ store char in buffer
    add r5,#1                                 @ increment location buffer
1:
    ldrb r3,[r0,r4]                           @read char[r4] in reg r3
    cmp r3,#0                                 @ if null  end
    beq 3f
    cmp r2,r3                                 @ compare two characters
    streqb r3,[r1,r5]                         @ = -> store char in buffer   
    beq 2f                                    @ loop

    mov r2,#','                               @ else store comma in buffer
    strb r2,[r1,r5]                           @ store char in buffer
    add r5,#1
    mov r2,#' '                               @ and store space in buffer
    strb r2,[r1,r5]
    add r5,#1
    strb r3,[r1,r5]                           @ and store input char in buffer
    mov r2,r3                                 @ and maj r2 with new char
2:
    add r5,#1                                 @ increment indices
    add r4,#1
    b 1b                                      @ and loop
3:
    strb r3,[r1,r5]                           @ store zero final in buffer
100:
    pop {r1-r5,lr}
    bx lr                                     @ return 

/******************************************************************/
/*     display text with size calculation                         */ 
/******************************************************************/
/* r0 contains the address of the message */
affichageMess:
    push {r0,r1,r2,r7,lr}                          @ save  registres
    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 systeme 
    pop {r0,r1,r2,r7,lr}                           @ restaur des  2 registres */ 
    bx lr                                          @ return  

output : gg, HHH, 5, YY, ++, ///, \

Arturo

parts: [] current: ""
loop split {gHHH5YY++///\} 'ch [
    if? or? empty? current
            contains? current ch -> 'current ++ ch
    else [
        'parts ++ current
        current: new ch
    ]
]
'parts ++ current
print parts
Output:
g HHH 5 YY ++ /// \

AutoHotkey

Split_Change(str){
	for i, v in StrSplit(str)
		res .= (v=prev) ? v : (res?", " :"") v	, prev := v
	return res
}
Examples:
str := "gHHH5YY++///\"
MsgBox % Split_Change(str)
Outputs:
g, HHH, 5, YY, ++, ///, \

RegEx Version

Split_Change(str){
	return RegExReplace(str, "(.)\1*(?!$)", "$0, ")
}
Examples:
str := "gHHH5YY++///\"
MsgBox % Split_Change(str)
Outputs:
g, HHH, 5, YY, ++, ///, \

AWK

# syntax: GAWK -f SPLIT_A_CHARACTER_STRING_BASED_ON_CHANGE_OF_CHARACTER.AWK
BEGIN {
    str = "gHHH5YY++///\\"
    printf("old: %s\n",str)
    printf("new: %s\n",split_on_change(str))
    exit(0)
}
function split_on_change(str,  c,i,new_str) {
    new_str = substr(str,1,1)
    for (i=2; i<=length(str); i++) {
      c = substr(str,i,1)
      if (substr(str,i-1,1) != c) {
        new_str = new_str ", "
      }
      new_str = new_str c
    }
    return(new_str)
}
Output:
old: gHHH5YY++///\
new: g, HHH, 5, YY, ++, ///, \

BaCon

Literal strings in BaCon are passed to the C compiler as they are; a backslash therefore needs to be escaped.

txt$ = "gHHH5YY++///\\"

c$ = LEFT$(txt$, 1)

FOR x = 1 TO LEN(txt$)
    d$ = MID$(txt$, x, 1)
    IF d$ <> c$ THEN
        PRINT ", ";
        c$ = d$
    END IF
    PRINT d$;
NEXT
Output:
g, HHH, 5, YY, ++, ///, \

BASIC256

function split$(instring$)
    if length(instring$) < 2 then return instring$
    ret$ = left(instring$,1)
        for i = 2 to length(instring$)
	    if mid(instring$,i,1) <> mid(instring$, i-1, 1) then ret$ += ", "
	    ret$ += mid(instring$, i, 1)
	next i
    return ret$
end function

print split$("gHHH5YY++///\")

BBC BASIC

REM >split
PRINT FN_split( "gHHH5YY++///\" )
END

DEF FN_split( s$ )
LOCAL c$, split$, d$, i%
c$ = LEFT$( s$, 1 )
split$ = ""
FOR i% = 1 TO LEN s$
  LET d$ = MID$( s$, i%, 1 )
  IF d$ <> c$ THEN
    split$ += ", "
    c$ = d$
  ENDIF
  split$ += d$
NEXT
= split$
Output:
g, HHH, 5, YY, ++, ///, \

C

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char *split(char *str);
int main(int argc,char **argv)
{
	char input[13]="gHHH5YY++///\\";
	printf("%s\n",split(input));
}
char *split(char *str)
{
	char last=*str,*result=malloc(3*strlen(str)),*counter=result;
	for (char *c=str;*c;c++) {
		if (*c!=last) {
			strcpy(counter,", ");
			counter+=2;
			last=*c;
		}
		*counter=*c;
		counter++;
	}
	*(counter--)='\0';
	return realloc(result,strlen(result));
}
Output:
g, HHH, 5, YY, ++, ///, \

C#

using System;
using System.Linq;
using System.Collections.Generic;

public class Program
{
    string s = @"gHHH5YY++///\";
    Console.WriteLine(s.RunLengthSplit().Delimit(", "));
}

public static class Extensions
{
    public static IEnumerable<string> RunLengthSplit(this string source) {
        using (var enumerator = source.GetEnumerator()) {
            if (!enumerator.MoveNext()) yield break;
            char previous = enumerator.Current;
            int count = 1;
            while (enumerator.MoveNext()) {
                if (previous == enumerator.Current) {
                    count++;
                } else {
                    yield return new string(Enumerable.Repeat(previous, count).ToArray());
                    previous = enumerator.Current;
                    count = 1;
                }
            }
            yield return new string(Enumerable.Repeat(previous, count).ToArray());
        }
    }

    public static string Delimit<T>(this IEnumerable<T> source, string separator = "") => string.Join(separator ?? "", source);
}
Output:
g, HHH, 5, YY, ++, ///, \

C++

// Solution for http://rosettacode.org/wiki/Split_a_character_string_based_on_change_of_character
#include<string>
#include<iostream>

auto split(const std::string& input, const std::string& delim){
	std::string res;
	for(auto ch : input){
		if(!res.empty() && ch != res.back())
			res += delim;
		res += ch;
	}
	return res;
}

int main(){
	std::cout << split("gHHH5  ))YY++,,,///\\", ", ") << std::endl;
}
Output:
g, HHH, 5,   , )), YY, ++, ,,,, ///, \

Clojure

(defn print-cchanges [s]
  (println (clojure.string/join ", " (map first (re-seq #"(.)\1*" s)))))

(print-cchanges "gHHH5YY++///\\")
Output:
g, HHH, 5, YY, ++, ///, \

CLU

% Split a string based on a change of character
split_on_change = iter (s: string) yields (string)
    part: string := ""
    for c: char in string$chars(s) do
        if ~string$empty(part) 
        cand part[string$size(part)] ~= c then 
            yield(part)
            part := ""
        end
        part := part || string$c2s(c)
    end
    yield(part)
end split_on_change 

start_up = proc ()
    po: stream := stream$primary_output()
    str: string := "gHHH5YYY++///\\" % \\ escapes, as in C
    rslt: string := ""
    first: bool := true
    
    for part: string in split_on_change(str) do
        if first then first := false
        else rslt := rslt || ", "
        end
        rslt := rslt || part
    end
    stream$putl(po, rslt)
end start_up
Output:
g, HHH, 5, YYY, ++, ///, \

COBOL

       identification division.
       program-id. split-ch.
       data division.
       1 split-str pic x(30) value space.
       88 str-1 value "gHHH5YY++///\".
       88 str-2 value "gHHH5  ))YY++,,,///\".
       1 binary.
        2 ptr pic 9(4) value 1.
        2 str-start pic 9(4) value 1.
        2 delim-len pic 9(4) value 1.
        2 split-str-len pic 9(4) value 0.
        2 trash-9 pic 9(4) value 0.
       1 delim-char pic x value space.
       1 delim-str pic x(6) value space.
       1 trash-x pic x.
       procedure division.
           display "Requested string"
           set str-1 to true
           perform split-init-and-go
           display space
           display "With spaces and commas"
           set str-2 to true
           perform split-init-and-go
           stop run
           .

       split-init-and-go.
           move 1 to ptr
           move 0 to split-str-len
           perform split
           .

       split.
           perform get-split-str-len
           display split-str (1:split-str-len)
           perform until ptr > split-str-len
               move ptr to str-start
               move split-str (ptr:1) to delim-char
               unstring split-str (1:split-str-len)
                   delimited all delim-char
                   into trash-x delimiter delim-str
                   pointer ptr
               end-unstring
               subtract str-start from ptr giving delim-len
               move split-str (str-start:delim-len)
                   to delim-str (1:delim-len)
               display delim-str (1:delim-len) with no advancing
               if ptr <= split-str-len
                   display ", " with no advancing
               end-if
           end-perform
           display space
           .

       get-split-str-len.
           inspect function reverse (split-str) tallying
               trash-9 for leading space
               split-str-len for characters after space
           .

       end program split-ch.
Output:
Requested string
gHHH5YY++///\
g, HHH, 5, YY, ++, ///, \

With spaces and commas
gHHH5  ))YY++,,,///\
g, HHH, 5,   , )), YY, ++, ,,,, ///, \

Common Lisp

(defun split (string)
  (loop :for prev := nil :then c
     :for c :across string
     :do (format t "~:[~;, ~]~c" (and prev (char/= c prev)) c)))

(split "gHHH5YY++///\\")
Output:
g, HHH, 5, YY, ++, ///, \

Doing more work that what's being ask, the following solution builds a list of strings then output it:

(defun split (string)
  (flet ((make-buffer ()
           (make-array 0 :element-type 'character :adjustable t :fill-pointer t)))
    (loop with buffer = (make-buffer)
          with result
          for prev = nil then c
          for c across string
          when (and prev (char/= c prev))
            do (push buffer result)
               (setf buffer (make-buffer))
          do (vector-push-extend c buffer)
          finally (push buffer result)
                  (format t "~{~A~^, ~}"(nreverse result)))))

(split "gHHH5YY++///\\")
Output:
g, HHH, 5, YY, ++, ///, \

Cowgol

include "cowgol.coh";

sub split(in: [uint8], buf: [uint8]): (out: [uint8]) is
    out := buf;
    loop
        [buf] := [in];
        if [in] == 0 then break; end if;
        if [in] != [@next in] and [@next in] != 0 then
            [buf+1] := ',';
            [buf+2] := ' ';
            buf := buf+2;
        end if;
        buf := buf+1;
        in := in+1;
    end loop;
end sub;

var buf: uint8[32];

print(split("gHHH5YY++//\\", &buf[0]));
print_nl();
Output:
g, HHH, 5, YY, ++, //, \

D

import std.stdio;

void main() {
    auto source = "gHHH5YY++///\\";

    char prev = source[0];
    foreach(ch; source) {
        if (prev != ch) {
            prev = ch;
            write(", ");
        }
        write(ch);
    }
    writeln();
}
Output:
g, HHH, 5, YY, ++, ///, \

Dyalect

func String.SmartSplit() {
    var c
    var str = ""
    var last = this.Length() - 1
 
    for n in 0..last {
        if c && this[n] != c {
            str += ", "
        }
        c = this[n]
        str += c
    }
 
    str
}
 
print("gHHH5YY++///\\".SmartSplit())
Output:
g, HHH, 5, YY, ++, ///, \

EasyLang

a$ = "gHHH5YY++///\\"
a$[] = strchars a$
cp$ = a$[0]
for c$ in a$[]
  if c$ <> cp$
    s$ &= ", "
    cp$ = c$
  .
  s$ &= c$
.
print s$
Output:
g, HHH, 5, YY, ++, ///, \

Elixir

split = fn str ->
          IO.puts " input string: #{str}"
          String.graphemes(str)
          |> Enum.chunk_by(&(&1))
          |> Enum.map_join(", ", &Enum.join &1)
          |> fn s -> IO.puts "output string: #{s}" end.()
        end

split.("gHHH5YY++///\\")
Output:
 input string: gHHH5YY++///\
output string: g, HHH, 5, YY, ++, ///, \

F#

open System.Text.RegularExpressions
let splitRuns s = Regex("""(.)\1*""").Matches(s) |> Seq.cast<Match> |> Seq.map (fun m -> m.Value) |> Seq.toList
printfn "%A" (splitRuns """gHHH5YY++///\""")
Output:
["g"; "HHH"; "5"; "YY"; "++"; "///"; "\"]

Factor

USE: splitting.monotonic
"gHHH5YY++///\\"
"aaabbccccdeeff" [ [ = ] monotonic-split ", " join print ] bi@
Output:
g, HHH, 5, YY, ++, ///, \
aaa, bb, cccc, d, ee, ff

Forth

Works with: Gforth version 0.7.3
CREATE A 0 ,               
: C@A+   A @ C@  [ 1 CHARS ]L A +! ;
: SPLIT. ( c-addr u --) SWAP A !  A @ C@
   BEGIN OVER WHILE
     C@A+  TUCK  <> IF ." , " THEN   
     DUP EMIT  SWAP 1- SWAP
   REPEAT  DROP ;
: TEST   OVER OVER
   ." input: " TYPE CR
   ." split: " SPLIT. CR ;
s" gHHH5YY++///\"        TEST
s" gHHH5  ))YY++,,,///\" TEST
BYE
Output:
input: gHHH5YY++///\
split: g, HHH, 5, YY, ++, ///, \
input: gHHH5  ))YY++,,,///\
split: g, HHH, 5,   , )), YY, ++, ,,,, ///, \

Fortran

This is F77 style, except for the END SUBROUTINE SPLATTER which would be just END, which for F90 is also allowable outside of the MODULE protocol. Linking the start/stop markers by giving the same name is helpful, especially when the compiler checks for this. The $ symbol at the end of a FORMAT code sequence is a common F77 extension, meaning "do not finish the line" so that a later output will follow on. This is acceptable to F90 and is less blather than adding the term ,ADVANCE = "NO" inside a WRITE statement that would otherwise be required. Output is to I/O unit 6 which is the modern default for "standard output". The format code is A meaning "any number of characters" rather than A1 for "one character" so as to accommodate not just the single character from TEXT but also the two characters of ", " for the splitter between sequences. Alas, there is no provision to change fount or colour for this, to facilitate the reader's attempts to parse the resulting list especially when the text includes commas or spaces of its own. By contrast, with quoted strings, the standard protocol is to double contained quotes.

An alternative method would be to prepare the entire output in a CHARACTER variable then write that, but this means answering the maddening question "how long is a piece of string?" for that variable, though later Fortran has arrangements whereby a text variable is resized to suit on every assignment, as in TEMP = TEMP // more - but this means repeatedly copying the text to the new manifestation of the variable. Still another approach would be to prepare an array of fingers to each split point (as in Phrase_reversals#Fortran) so that the final output would be a single WRITE using that array, and again, how big must the array be? At most, as big as the number of characters in TEXT. With F90, subroutines can declare arrays of a size determined on entry, with something like INTEGER A(LEN(TEXT))

If the problem were to be solved by writing a "main line" only, there would have to be a declaration of the text variable there but since a subroutine can receive a CHARACTER variable of any size (the actual size is passed as a secret parameter), this can be dodged.

For this example a DO-loop stepping along the text is convenient, but in a larger context it would probably be most useful to work along the text with fingers L1 and L2 marking the start and finish positions of each sequence.
      SUBROUTINE SPLATTER(TEXT)	!Print a comma-separated list. Repeated characters constitute one item.
Can't display the inserted commas in a different colour so as not to look like any commas in TEXT.
       CHARACTER*(*) TEXT	!The text.
       INTEGER L	!A finger.
       CHARACTER*1 C	!A state follower.
        IF (LEN(TEXT).LE.0) RETURN	!Prevent surprises in the following..
        C = TEXT(1:1)			!Syncopation: what went before.
        DO L = 1,LEN(TEXT)	!Step through the text.
          IF (C.NE.TEXT(L:L)) THEN	!A change of character?
            C = TEXT(L:L)			!Yes. This is the new normal.
            WRITE (6,1) ", "			!Set off from what went before. This is not from TEXT.
          END IF			!So much for changes.
          WRITE (6,1) C			!Roll the current character. (=TEXT(L:L))
    1     FORMAT (A,$)			!The $ sez: do not end the line.
        END DO			!On to the next character.
        WRITE (6,1)	!Thus end the line. No output item means that the $ is not reached, so the line is ended.
      END SUBROUTINE SPLATTER	!TEXT with spaces, or worse, commas, will produce an odd-looking list.

      PROGRAM POKE
      CALL SPLATTER("gHHH5YY++///\")	!The example given.
      END

Unfortunately, the syntax highlighter has failed to notice the terminating quote character, presumably because the preceding backslash might be an "escape sequence" trigger, a facility not used in Fortran text literals except possibly as a later modernist option.

Output:
g, HHH, 5, YY, ++, ///, \

FreeBASIC

function split( instring as string ) as string
    if len(instring) < 2 then return instring
    dim as string ret = left(instring,1)
    for i as uinteger = 2 to len(instring)
        if mid(instring,i,1)<>mid(instring, i - 1, 1) then ret + = ", "
        ret += mid(instring, i, 1)
    next i
    return ret
end function

Frink

s = "gHHH5YY++///\\"
println[join[", ", map[getFunction["first", 1], s =~ %r/((.)\2*)/g]]]
Output:
g, HHH, 5, YY, ++, ///, \

FutureBasic

FB can process either Pascal strings (slowly being deprecated), or Apple's Core Foundation CFStrings (and Objective-C NSStrings). Here's the old-school Pascal string function:

local fn SplitString( inputStr as Str255 ) as Str255
Str255     resultStr
NSUInteger i

if len$( inputStr ) < 2 then resultStr = inputStr : exit fn
resultStr = left$( inputStr, 1 )
for i = 2 to len$( inputStr )
  if mid$( inputStr, i, 1 ) <> mid$( inputStr, i - 1, 1 ) then resultStr = resultStr + ", "
  resultStr = resultStr + mid$(inputStr, i, 1)
next
end fn = resultStr

window 1

print fn SplitString( "gHHH5YY++///\" )

HandleEvents

And here's the recommended CFString counterpart:

local fn SplitString( inputStr as CFStringRef ) as CFStringRef
  NSUInteger         i
  unichar            chr, lastChr = fn StringCharacterAtIndex( inputStr, 0 )
  CFMutableStringRef resultStr    = fn MutableStringWithCapacity(0)
  
  for i = 0 to len( inputStr ) - 1
    chr = fn StringCharacterAtIndex( inputStr, i )
    if ( chr != lastChr ) then MutableStringAppendString( resultStr, @", " )
    MutableStringAppendString( resultStr, mid( inputStr, i, 1 ) )
    lastChr = chr
  next
end fn = resultStr

window 1

print fn SplitString( @"gHHH5YY++///\\" )

HandleEvents

Output for either function:

g, HHH, 5, YY, ++, ///, \

Go

Treating "character" as a byte:

package main

import (
    "fmt"
    "strings"
)

func main() {
    fmt.Println(scc(`gHHH5YY++///\`))
}

func scc(s string) string {
    if len(s) < 2 {
        return s
    }
    var b strings.Builder
    p := s[0]
    b.WriteByte(p)
    for _, c := range []byte(s[1:]) {
        if c != p {
            b.WriteString(", ")
        }
        b.WriteByte(c)
        p = c
    }
    return b.String()
}
Output:
g, HHH, 5, YY, ++, ///, \


Haskell

import Data.List (group, intercalate)

main :: IO ()
main = putStrLn $ intercalate ", " (group "gHHH5YY++///\\")
Output:
g, HHH, 5, YY, ++, ///, \

or as a hand-written fold:

import Data.List (intercalate)
import Data.Bool (bool)

charGroups :: String -> [String]
charGroups =
  let go (a, b) (s, groups)
        | a == b = (b : s, groups)
        | otherwise =
            ( [a],
              bool s [b] (null s) : groups
            )
   in uncurry (:) . foldr go ([], []) . (zip <*> tail)

main :: IO ()
main =
  putStrLn $ intercalate ", " $ charGroups "gHHH5YY++///\\"
g, HHH, 5, YY, ++, ///, \

or in terms of span:

import Data.List (intercalate)

charGroups :: String -> [String]
charGroups [] = []
charGroups (c : cs) =
  let (xs, ys) = span (c ==) cs
   in (c : xs) : charGroups ys

main :: IO ()
main =
  putStrLn $ intercalate ", " $ charGroups "gHHH5YY++///\\"
Output:
g, HHH, 5, YY, ++, ///, \

IS-BASIC

100 LET S$="gHHH5YY++///\"
110 PRINT S$(1);
120 FOR I=2 TO LEN(S$)
130   IF S$(I)<>S$(I-1) THEN PRINT ", ";
140   PRINT S$(I);
150 NEXT
160 PRINT

J

Solution:

splitChars=: (1 ,~ 2 ~:/\ ]) <;.2 ]
delimitChars=: ', ' joinstring splitChars

Example Usage:

   delimitChars 'gHHH5YY++///\'
g, HHH, 5, YY, ++, ///, \

Java

package org.rosettacode;

import java.util.ArrayList;
import java.util.List;


/**
 * This class provides a main method that will, for each arg provided,
 * transform a String into a list of sub-strings, where each contiguous
 * series of characters is made into a String, then the next, and so on,
 * and then it will output them all separated by a comma and a space.
 */
public class SplitStringByCharacterChange {
    
    public static void main(String... args){
        for (String string : args){
            
            List<String> resultStrings = splitStringByCharacter(string);
            String output = formatList(resultStrings);
            System.out.println(output);
        }
    }
    
    /**
     * @param string String - String to split
     * @return List<\String> - substrings of contiguous characters
     */
    public static List<String> splitStringByCharacter(String string){
        
        List<String> resultStrings = new ArrayList<>();
        StringBuilder currentString = new StringBuilder();
        
        for (int pointer = 0; pointer < string.length(); pointer++){
            
            currentString.append(string.charAt(pointer));
            
            if (pointer == string.length() - 1 
                    || currentString.charAt(0) != string.charAt(pointer + 1)) {
                resultStrings.add(currentString.toString());
                currentString = new StringBuilder();
            }
        }
        
        return resultStrings;
    }
    
    /**
     * @param list List<\String> - list of strings to format as a comma+space-delimited string
     * @return String
     */
    public static String formatList(List<String> list){
        
        StringBuilder output = new StringBuilder();
        
        for (int pointer = 0; pointer < list.size(); pointer++){
            output.append(list.get(pointer));
            
            if (pointer != list.size() - 1){
                output.append(", ");
            }
        }
        
        return output.toString();
    }
}
Output:
g, HHH, 5, YY, ++, ///, \

JavaScript

ES6

Translation of: Haskell
(() => {
    "use strict";

    // ----------- SPLIT ON CHARACTER CHANGES ------------
    const main = () =>
        group("gHHH5YY++///\\")
        .map(x => x.join(""))
        .join(", ");


    // --------------------- GENERIC ---------------------

    // group :: [a] -> [[a]]
    const group = xs =>
        // A list of lists, each containing only
        // elements equal under (===), such that the
        // concatenation of these lists is xs.
        groupBy(a => b => a === b)(xs);


    // groupBy :: (a -> a -> Bool) [a] -> [[a]]
    const groupBy = eqOp =>
        // A list of lists, each containing only elements
        // equal under the given equality operator,
        // such that the concatenation of these lists is xs.
        xs => 0 < xs.length ? (() => {
            const [h, ...t] = xs;
            const [groups, g] = t.reduce(
                ([gs, a], x) => eqOp(x)(a[0]) ? (
                    Tuple(gs)([...a, x])
                ) : Tuple([...gs, a])([x]),
                Tuple([])([h])
            );

            return [...groups, g];
        })() : [];


    // Tuple (,) :: a -> b -> (a, b)
    const Tuple = a =>
        b => ({
            type: "Tuple",
            "0": a,
            "1": b,
            length: 2,
            *[Symbol.iterator]() {
                for (const k in this) {
                    if (!isNaN(k)) {
                        yield this[k];
                    }
                }
            }
        });

    // MAIN ---
    return main();
})();
Output:
g, HHH, 5, YY, ++, ///, \


Or, in terms of a general `span` function:

(() => {
    "use strict";

    // -------- STRING SPLIT ON CHARACTER CHANGES --------

    // charGroups :: String -> [String]
    const charGroups = s =>
        // The characters of s split at each point where
        // consecutive characters differ.
        0 < s.length ? (() => {
            const
                c = s[0],
                [xs, ys] = span(x => c === x)([
                    ...s.slice(1)
                ]);

            return [
                    [c, ...xs], ...charGroups(ys)
                ]
                .map(zs => [...zs].join(""));
        })() : "";


    // ---------------------- TEST -----------------------
    // main :: IO()
    const main = () =>
        charGroups("gHHH5YY++///\\")
        .join(", ");


    // --------------------- GENERIC ---------------------

    // span :: (a -> Bool) -> [a] -> ([a], [a])
    const span = p =>
        // Longest prefix of xs consisting of elements which
        // all satisfy p, tupled with the remainder of xs.
        xs => {
            const i = xs.findIndex(x => !p(x));

            return -1 !== i ? [
                xs.slice(0, i),
                xs.slice(i)
            ] : [xs, []];
        };

    // MAIN ---
    return main();
})();
Output:
g, HHH, 5, YY, ++, ///, \

jq

# input: a string
# output: a stream of runs
def runs:
  def init:
    explode as $s
    | $s[0] as $i
    | (1 | until( $s[.] != $i; .+1));
  if length == 0 then empty
  elif length == 1 then .
  else init as $n | .[0:$n], (.[$n:] | runs)
  end;

"gHHH5YY++///\\" | [runs] | join(", ")
Output:

Using the -r ("raw output") command-line option of jq:

g, HHH, 5, YY, ++, ///, \

Jsish

Showing off a little unit testing...

Starting with

#!/usr/bin/env jsish
;'Split a string based on change of character, in Jsish';

function splitOnChange(str:string):string {
    if (str.length < 2) return str;
    var last = str[0];
    var result = last;
    for (var pos = 1; pos < str.length; pos++) {
        result += ((last == str[pos]) ? last : ', ' + str[pos]);
        last = str[pos];
    }
    return result;
}
provide('splitOnChange', 1.0);

/* literal backslash needs escaping during initial processing */
;splitOnChange('gHHH5YY++///\\');
;splitOnChange('a');
;splitOnChange('ab');
;splitOnChange('aaa');
;splitOnChange('aaaba');
;splitOnChange('gH HH5YY++//,/\\');

Then

prompt$ jsish -u -update true splitOnChange.jsi
Created splitOnChange.jsi

Giving

#!/usr/bin/env jsish
;'Split a string based on change of character, in Jsish';

function splitOnChange(str:string):string {
    if (str.length < 2) return str;
    var last = str[0];
    var result = last;
    for (var pos = 1; pos < str.length; pos++) {
        (last == str[pos]) ? result += last : result += ', ' + str[pos];
        last = str[pos];
    }
    return result;
}
provide('splitOnChange', 1.0);

/* literal backslash needs escaping during initial processing */
;splitOnChange('gHHH5YY++///\\');
;splitOnChange('a');
;splitOnChange('ab');
;splitOnChange('aaa');
;splitOnChange('aaaba');
;splitOnChange('gH HH5YY++//,/\\');

/*
=!EXPECTSTART!=
'Split a string based on change of character, in Jsish'
splitOnChange('gHHH5YY++///\') ==> g, HHH, 5, YY, ++, ///, \
splitOnChange('a') ==> a
splitOnChange('ab') ==> a, b
splitOnChange('aaa') ==> aaa
splitOnChange('aaaba') ==> aaa, b, a
splitOnChange('gH HH5YY++//,/\') ==> g, H,  , HH, 5, YY, ++, //, ,, /, \
=!EXPECTEND!=
*/

Which tests as:

prompt$ jsish -u splitOnChange.jsi
[PASS] splitOnChange.jsi

And then satisfying the task of showing the one result, using the script as a module:

Output:
prompt$ jsish
Jsish interactive: see 'help [cmd]'.  \ cancels > input.  ctrl-c aborts running script.
# require('splitOnChange');
1
# puts(splitOnChange('gHHH5YY++///\\'));
g, HHH, 5, YY, ++, ///, \

Julia

# v0.6
using IterTools

str = "gHHH5YY++///\\"
sep = map(join, groupby(identity, str))
println("string: $str\nseparated: ", join(sep, ", "))
Output:
string: gHHH5YY++///\
separated: g, HHH, 5, YY, ++, ///, \

Kotlin

// version 1.0.6

fun splitOnChange(s: String): String {
    if (s.length < 2) return s
    var t = s.take(1)  
    for (i in 1 until s.length)
        if (t.last() == s[i]) t += s[i]
        else t += ", " + s[i] 
    return t
}

fun main(args: Array<String>) {
    val s = """gHHH5YY++///\"""
    println(splitOnChange(s))
}
Output:
g, HHH, 5, YY, ++, ///, \

Lambdatalk

{def mysplit
 {def mysplit.r
  {lambda {:w :i}
   {if {> :i {W.length :w}}
    then 
    else {if {not {W.equal? {W.get :i :w} {W.get {+ :i 1} :w}}}
          then ____ else} {W.get {+ :i 1} :w}{mysplit.r :w {+ :i 1}}}}}
 {lambda {:w}
  {S.replace ____ by in {mysplit.r #:w 0}}}}
-> mysplit

{mysplit gHHH5YY++///\}
->  g HHH 5 YY ++ /// \

Lua

Note that the backslash must be quoted as a double backslash as Lua uses C-like escape sequences.

function charSplit (inStr)
    local outStr, nextChar = inStr:sub(1, 1)
    for pos = 2, #inStr do
        nextChar = inStr:sub(pos, pos)
        if nextChar ~= outStr:sub(#outStr, #outStr) then
            outStr = outStr .. ", "
        end
        outStr = outStr .. nextChar
    end
    return outStr
end

print(charSplit("gHHH5YY++///\\"))
Output:
g, HHH, 5, YY, ++, ///, \

Alternative: Simply scan difference in reverse order and insert delimiter in place, the loop counter i will not update with length of s.

function splitdiff(s)
  for i=#s,2,-1 do
    if s:sub(i,i)~=s:sub(i-1,i-1) then
      s = s:sub(1,i-1)..', '.. s:sub(i,-1)
    end
  end
  return s
end

Ksh

#!/bin/ksh

# Split a character string based on change of character

#	# Variables:
#
str='gHHH5YY++///\'
delim=', '

#	# Functions:
#
#	# Function _splitonchg(str, delim) - return str split by delim at char change
#
function _splitonchg {
	typeset _str ; _str="$1"
	typeset _delim ; _delim="$2"
	typeset _i _splitstr ; integer _i

	for ((_i=1; _i<${#_str}+1; _i++)); do
		if [[ "${_str:$((_i-1)):1}" != "${_str:${_i}:1}" ]]; then
			_splitstr+="${_str:$((_i-1)):1}${_delim}"
		else
			_splitstr+="${_str:$((_i-1)):1}"
		fi
	done
	echo "${_splitstr%"${_delim}"*}"
}

 ######
# main #
 ######

print "Original: ${str}"
print "   Split: $(_splitonchg "${str}" "${delim}")"
Output:

Original: gHHH5YY++///\

Split: g, HHH, 5, YY, ++, ///, \

M2000 Interpreter

Stack New open a new stack object as current stack, and keep the old one. After the end of block execution old stack get back as current stack. Data statement push to bottom (we read from top, so using data we get a FIFO type). Letter$ pops a string or raise an error if no string found at the top of stack.

Module PrintParts(splitthis$) {
      Def string m$, p$
      Def long c
      Stack New {
            if len(splitthis$)=0 then exit
            For i=1 to len(splitthis$)
                  p$=mid$(splitthis$,i,1)
                  if m$<>p$ then {
                        if c>0 then data string$(m$, c)
                        m$=p$
                        c=1
                  } else c++
            Next i
            if c>0 then data string$(m$, c)
            While stack.size>1 {
                  Print letter$+", ";
            }
            If not empty then Print letter$
      }
}
PrintParts "gHHH5YY++///\"

Maple

Added an additional backlash to escape the \ character at the end.

splitChange := proc(str::string)
	local start,i,len;
	start := 1;
	len := StringTools:-Length(str);
	for i from 2 to len do
		if str[i] <> str[start] then
			printf("%s, ",  str[start..i-1]);
			start := i:
		end if;
	end do;
	printf("%s", str[start..len]);
end proc;
splitChange("gHHH5YY++///\\");
Output:
g, HHH, 5, YY, ++, ///, \

Mathematica/Wolfram Language

The backslash (\) must be escaped with another backslash when defining the string.

StringJoin@@Riffle[StringCases["gHHH5YY++///\\", p : (x_) .. -> p], ", "]
Output:
g, HHH, 5, YY, ++, ///, \

MiniScript

s = "gHHH5YY++///\"
output = []
lastLetter = s[0]
for letter in s
    if letter != lastLetter then output.push ", "
    output.push letter
    lastLetter = letter
end for
print output.join("")
Output:
g, HHH, 5, YY, ++, ///, \

Modula-2

MODULE CharacterChange;
FROM Terminal IMPORT Write,WriteString,WriteLn,ReadChar;

PROCEDURE Split(str : ARRAY OF CHAR);
VAR
    i : CARDINAL;
    c : CHAR;
BEGIN
    FOR i:=0 TO HIGH(str) DO
        IF i=0 THEN
            c := str[i]
        ELSIF str[i]#c THEN
            c := str[i];
            WriteLn;
        END;
        Write(c)
    END
END Split;

CONST EX = "gHHH5YY++///\";
BEGIN
    Split(EX);

    ReadChar
END CharacterChange.
Output:
g
HHH
5
YY
++
///
\

Nim

proc splitOnDiff(str: string): string =
  result = ""

  if str.len < 1: return result

  var prevChar: char = str[0]

  for idx in 0 ..< str.len:
    if str[idx] != prevChar:
      result &= ", "
      prevChar = str[idx]

    result &= str[idx]

assert splitOnDiff("""X""") == """X"""
assert splitOnDiff("""XX""") == """XX"""
assert splitOnDiff("""XY""") == """X, Y"""
assert splitOnDiff("""gHHH5YY++///\""") == """g, HHH, 5, YY, ++, ///, \"""

echo splitOnDiff("""gHHH5YY++///\""")
Output:
g, HHH, 5, YY, ++, ///, \

ooRexx

Parse Arg str  .                                  /*obtain optional arguments from the CL*/
If str=='' Then str= 'gHHH5YY++///\'        /*Not specified?  Then use the default.*/
i=1
ol=''
Do Forever
  j=verify(str,substr(str,i,1),'N',i,99)  /* find first character that's different */
  If j=0 Then Do                          /* End of strin reached                  */
    ol=ol||substr(str,i)                  /* the final substring                   */
    Leave
    End
  ol=ol||substr(str,i,j-i)', '            /* add substring and delimiter           */
  i=j
  End
Say ol
Output:
g, HHH, 5, YY, ++, ///, \

Pascal

program SplitChars;
{$IFDEF FPC}
  {$MODE DELPHI}{$COPERATORS ON}
{$ENDIF}
const
  TestString =  'gHHH5YY++///\';

function SplitAtChars(const S: String):String;
var
  i : integer;
  lastChar:Char;
begin
  result := '';
  IF length(s) > 0 then
  begin
    LastChar := s[1];
    result := LastChar;
    For i := 2 to length(s) do
    begin
      if s[i] <> lastChar then
      begin
        lastChar := s[i];
        result += ', ';
      end;
      result += LastChar;
    end;
  end;
end;

BEGIN
  writeln(SplitAtChars(TestString));
end.
Output:
g, HHH, 5, YY, ++, ///, \

Perl

use strict;
use warnings;
use feature 'say';
use utf8;
binmode(STDOUT, ':utf8');

for my $string (q[gHHH5YY++///\\], q[fffn⃗n⃗n⃗»»»  ℵℵ☄☄☃☃̂☃🤔🇺🇸🤦♂️👨‍👩‍👧‍👦]) {
    my @S;
    my $last = '';
    while ($string =~ /(\X)/g) {
        if ($last eq $1) { $S[-1] .= $1 } else { push @S, $1 }
        $last = $1;
    }
    say "Orginal: $string\n  Split: 「" . join('」, 「', @S) . "」\n";
}
Output:
Orginal: gHHH5YY++///\
  Split: 「g」, 「HHH」, 「5」, 「YY」, 「++」, 「///」, 「\」

Orginal: fffn⃗n⃗n⃗»»»  ℵℵ☄☄☃☃̂☃🤔🇺🇸🤦♂️👨‍👩‍👧‍👦
  Split: 「fff」, 「」, 「n⃗n⃗n⃗」, 「»»»」, 「  」, 「ℵℵ」, 「☄☄」, 「☃」, 「☃̂」, 「☃」, 「🤔」, 「🇺🇸」, 「🤦♂️」, 「👨‍👩‍👧‍👦」

Phix

function split_on_change(string s)
    string res = ""
    if length(s) then
        integer prev = s[1]
        for i=1 to length(s) do
            integer ch = s[i]
            if ch!=prev then
                res &= ", "
                prev = ch
            end if
            res &= ch
        end for
    end if
    return res
end function
 
puts(1,split_on_change(`gHHH5YY++///\`))
Output:
g, HHH, 5, YY, ++, ///, \

PicoLisp

(de splitme (Str)
   (let (Str (chop Str)  Fin)
      (glue
         ", "
         (make
            (for X Str
               (if (= X (car Fin))
                  (conc Fin (cons X))
                  (link (setq Fin (cons X))) ) ) ) ) ) )
(prinl (splitme "gHHH5YY++///\\"))
Output:
g, HHH, 5, YY, ++, ///, \

Pike

string input = "gHHH5YY++///\\"; // \ needs escaping
string last_char;
foreach(input/1, string char) {
    if(last_char && char != last_char)
        write(", ");
    write(char);
    last_char = char;
}
Output:
g, HHH, 5, YY, ++, ///, \

Plain English

To make sense of this example, you must understand riders. A rider is a simple abstraction for efficiently parsing strings. A rider is a record with an original substring, a source substring, and a token substring.

After executing the following code, for example:

Put "abcdef" into a string.
Slap a rider on the string.

The rider looks like this:

Original: "abcdef"
Source: "abcdef"
Token: ""

Now when we Bump the rider., it looks like this:

Original: "abcdef"
Source: "bcdef"
Token: "a"

Another bump, and:

Original: "abcdef"
Source: "cdef"
Token: "ab"

Now let's say we have a complete token and want to start a new one. We can Position the rider's token on the rider's source. and now the rider looks like this:

Original: "abcdef"
Source: "cdef"
Token: ""

And that's all there is to it.

To run:
Start up.
Split "gHHH5YY++///\" into some string things by change of character.
Write the string things on the console.
Destroy the string things.
Wait for the escape key.
Shut down.

To split a string into some string things by change of character:
If the string's length is less than 2, add the string to the string things; exit.
Slap a rider on the string.
Loop.
Move the rider (change of character rules).
Add the rider's token to the string things.
If the rider's source is blank, exit.
Repeat.

To move a rider (change of character rules):
Position the rider's token on the rider's source.
Loop.
If the rider's source is blank, exit.
If the rider's token is blank, bump the rider; repeat.
Put the rider's token's last plus 1 into a byte pointer.
If the rider's token's last's target is not the byte pointer's target, exit.
Bump the rider.
Repeat.

To write some string things to a console;
To write some string things on a console:
Get a string thing from the string things.
Loop.
If the string thing is nil, write "" on the console; exit.
Write the string thing's string on the console without advancing.
If the string thing's next is not nil, write ", " on the console without advancing.
Put the string thing's next into the string thing.
Repeat.
Output:
g, HHH, 5, YY, ++, ///, \

PowerShell

Translation of: BBC BASIC
function Split-String ([string]$String)
{
    [string]$c = $String.Substring(0,1)
    [string]$splitString = $c

    for ($i = 1; $i -lt $String.Length; $i++)
    { 
        [string]$d = $String.Substring($i,1)

        if ($d -ne $c)
        {
            $splitString += ", "
            $c = $d
        }

        $splitString += $d
    }

    $splitString
}
Split-String "gHHH5YY++///\"
Output:
g, HHH, 5, YY, ++, ///, \

PureBasic

Procedure splitstring(s$)
  Define *p.Character = @s$,
         c_buf.c = *p\c  
  While *p\c
    If *p\c = c_buf      
      Print(Chr(c_buf))
    Else
      Print(", ")
      c_buf = *p\c
      Continue
    EndIf
    *p + SizeOf(Character)
  Wend
EndProcedure

If OpenConsole()
  splitstring("gHHH5YY++///\")
  Input()
EndIf
Output:
g, HHH, 5, YY, ++, ///, \

Python

Python3.6+

Using [itertools.groupby].

from itertools import groupby

def splitter(text):
    return ', '.join(''.join(group) for key, group in groupby(text))

if __name__ == '__main__':
    txt = 'gHHH5YY++///\\'      # Note backslash is the Python escape char.
    print(f'Input: {txt}\nSplit: {splitter(txt)}')
Output:
Input: gHHH5YY++///\
Split: g, HHH, 5, YY, ++, ///, \

Python: Using zip

def splitterz(text):
    return (''.join(x + ('' if x == nxt else ', ') 
            for x, nxt in zip(txt, txt[1:] + txt[-1])))

if __name__ == '__main__':
    txt = 'gHHH5YY++///\\'
    print(splitterz(txt))
Output:
g, HHH, 5, YY, ++, ///, \

Python2

import itertools

try: input = raw_input
except: pass

s = input()
groups = []
for _, g in itertools.groupby(s):
    groups.append(''.join(g))
print('      input string:  %s' % s)
print('     output string:  %s' % ', '.join(groups))
Output:
  when using the default input
      input string:  gHHH5YY++///\
     output string:  g, HHH, 5, YY, ++, ///, \

Quackery

[ dup size 2 < 
  iff size done
  behead swap
  [] nested join
  witheach
    [ over != if 
      [ drop i^ 1+
        conclude ] ] ] is $run  ( $ --> n )

[ dup size 2 < if done
  dup $run split
  dup [] = 
  iff drop done
  dip [ $ ", " join ]
  recurse join ]       is runs$ ( $ --> $ )

Testing in Quackery shell.

/O> $ "gHHH5YY++///\" runs$ echo$
... 
g, HHH, 5, YY, ++, ///, \
Stack empty.

Racket

Translation of: Python
#lang racket
(define (split-strings-on-change s)
  (map list->string (group-by values (string->list s) char=?)))

(displayln (string-join (split-strings-on-change #<<<
gHHH5YY++///\
<
                                                 )
                        ", "))
Output:
g, HHH, 5, YY, ++, ///, \

Raku

(formerly Perl 6)

Works with: Rakudo version 2017.05
sub group-chars ($str) { $str.comb: / (.) $0* / }

# Testing:

for Q[gHHH5YY++///\], Q[fffn⃗n⃗n⃗»»»  ℵℵ☄☄☃☃̂☃🤔🇺🇸🤦‍♂️👨‍👩‍👧‍👦] -> $string {
    put 'Original: ', $string;
    put '   Split: ', group-chars($string).join(', ');
}
Output:
Original: gHHH5YY++///\
   Split: g, HHH, 5, YY, ++, ///, \
Original: fffn⃗n⃗n⃗»»»  ℵℵ☄☄☃☃̂☃🤔🇺🇸🤦‍♂️👨‍👩‍👧‍👦
   Split: fff, , n⃗n⃗n⃗, »»»,   , ℵℵ, ☄☄, ☃, ☃̂, ☃, 🤔, 🇺🇸, 🤦‍♂️, 👨‍👩‍👧‍👦

The second test-case is to show that Raku works with strings on the Unicode grapheme level, handles whitespace, combiners, and zero width characters up to Unicode Version 13.0 correctly. (Raku generally tracks updates to the Unicode spec and typically lags no more than a month behind.) For those of you with browsers unable to display the second string, it consists of:

  • {LATIN SMALL LETTER F} x 3
  • {ZERO WIDTH NO-BREAK SPACE} x 3
  • {LATIN SMALL LETTER N, COMBINING RIGHT ARROW ABOVE} x 3
  • {RIGHT-POINTING DOUBLE ANGLE QUOTATION MARK} x 3
  • {SPACE} x 2,
  • {ALEF SYMBOL} x 2,
  • {COMET} x 2,
  • {SNOWMAN} x 1,
  • {SNOWMAN, COMBINING CIRCUMFLEX ACCENT} x 1
  • {SNOWMAN} x 1,
  • {THINKING FACE} x 1
  • {REGIONAL INDICATOR SYMBOL LETTER U, REGIONAL INDICATOR SYMBOL LETTER S} x 1
  • {FACE PALM, ZERO WIDTH JOINER, MALE SIGN, VARIATION SELECTOR-16} x 1
  • {MAN, ZERO WIDTH JOINER, WOMAN, ZERO WIDTH JOINER, GIRL, ZERO WIDTH JOINER, BOY} x 1

REXX

version 1

/*REXX program splits a string based on change of character ───► a comma delimited list.*/
parse arg str                                    /*obtain optional arguments from the CL*/
if str==''  then str= 'gHHH5YY++///\'            /*Not specified?  Then use the default.*/
p=left(str, 1)                                   /*placeholder for the "previous" string*/
$=                                               /*     "       "   "    output      "  */
     do j=1  for length(str);  @=substr(str,j,1) /*obtain a character from the string.  */
     if @\==p  then $=$', '                      /*Not replicated char? Append delimiter*/
     p=@;           $=$ || @                     /*append a character to the  $  string.*/
     end   /*j*/                                 /* [↓]  keep peeling chars until done. */
say '          input string: '      str          /*display the original string & output.*/
say '         output string: '      $            /*stick a fork in it,  we're all done. */
output   when using the default input:
          input string:  gHHH5YY++///\
         output string:  g, HHH, 5, YY, ++, ///, \

version 2

/* REXX */
Parse arg str                         /*obtain optional arguments from the CL*/
if str==''  then str= 'gHHH5YY++///\' /*Not specified?  Then use the default.*/
input=str
x=''
cp=''
result=''
Do While str<>''
  Parse Var str c +1 str
  If c==cp Then x=x||c
  Else Do
    If x>>'' Then
      result=result||x', '
    x=c
    End
  cp=c
  End
result=result||x
say '      input string: '    input
say '     output string: '    result

{{out]]

      input string:  gHHH5YY++///\
     output string:  g, HHH, 5, YY, ++, ///, \

Ring

see split("gHHH5YY++///\")

func split(s )
     c =left (s, 1)
     split = ""
     for i = 1 to len(s)
         d = substr(s, i, 1)
         if d != c
            split = split + ", "
            c = d 
         ok
         split = split + d 
     next
     return split

Output:

g, HHH, 5, YY, ++, ///, \

Ruby

def split(str)
  puts " input string: #{str}"
  s = str.chars.chunk(&:itself).map{|_,a| a.join}.join(", ")
  puts "output string: #{s}"
  s
end

split("gHHH5YY++///\\")
Output:
 input string: gHHH5YY++///\
output string: g, HHH, 5, YY, ++, ///, \

Rust

fn splitter(string: &str) -> String {
    let chars: Vec<_> = string.chars().collect();
    let mut result = Vec::new();
    let mut last_mismatch = 0;
    for i in 0..chars.len() {
        if chars.len() == 1 {
            return chars[0..1].iter().collect();
        }
        if i > 0 && chars[i-1] != chars[i] {
            let temp_result: String = chars[last_mismatch..i].iter().collect();
            result.push(temp_result);
            last_mismatch = i;
        }
        if i == chars.len() - 1 {
            let temp_result: String = chars[last_mismatch..chars.len()].iter().collect();
            result.push(temp_result);
        }
    }
    result.join(", ")
}

fn main() {
    let test_string = "g";
    println!("input string: {}", test_string);
    println!("output string: {}", splitter(test_string));

    let test_string = "";
    println!("input string: {}", test_string);
    println!("output string: {}", splitter(test_string));

    let test_string = "gHHH5YY++///\\";
    println!("input string: {}", test_string);
    println!("output string: {}", splitter(test_string));
}
Output:
input string: g
output string: g
input string: 
output string: 
input string: gHHH5YY++///\
output string: g, HHH, 5, YY, ++, ///, \

Alternate using IterTools

use itertools::Itertools;

pub fn split_text(s: &str) -> Vec<String> {
    let mut r = Vec::new();
    for (_, group) in &s.chars().into_iter().group_by(|e| *e) {
        r.push(group.map(|e| e.to_string()).join(""));
    }
    r
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_splitting_text() {
        assert_eq!(split_text("gHHH5YY++///\\"), vec!["g", "HHH", "5", "YY", "++", "///", "\\"]);
        assert!(split_text("").is_empty());
    }
}

Scala

// Split a (character) string into comma (plus a blank) delimited strings
// based on a change of character (left to right).
// See https://rosettacode.org/wiki/Split_a_character_string_based_on_change_of_character#Scala

def runLengthSplit(s: String): String = /// Add a guard letter
  (s + 'X').sliding(2).map(pair => pair.head + (if (pair.head != pair.last) ", " else "")).mkString("")

println(runLengthSplit("""gHHH5YY++///\"""))
Output:
See it in running in your browser by ScalaFiddle (JavaScript)

or by Scastie (JVM).

def runLengthSplit(s:String):List[String] = {
  def recursiveSplit(acc:List[String], rest:String): List[String] = rest match {
    case "" => acc
    case _ => {
      val (h, t) = rest.span(_ == rest.head)
      recursiveSplit(acc :+ h, t)
    }
  }

  recursiveSplit(Nil, s)
}

val result = runLengthSplit("""gHHH5YY++///\""")
println(result.mkString(","))
Output:
g,HHH,5,YY,++,///,\

Sed

echo 'gHHH5YY++///\' | sed 's/\(.\)\1*/&, /g;s/, $//'

Output:

g, HHH, 5, YY, ++, ///, \

Sidef

func group(str) {
    gather {
        while (var match = (str =~ /((.)\g{-1}*)/g)) {
            take(match[0])
        }
    }
}

say group(ARGV[0] \\ 'gHHH5YY++///\\').join(', ')
Output:
g, HHH, 5, YY, ++, ///, \

SNOBOL4

* Program: split_on_change_of_character.sbl
* To run: sbl split_on_change_of_character.sbl
* Description: Split a (character) string into comma (plus a blank)
* delimited strings based on a change of character   (left to right).
*
* Blanks should be treated as any other character
* (except they are problematic to display clearly).
* The same applies to commas.
*
* For instance, the string:
*
* gHHH5YY++///\ 
* should be split and show:
*
* g, HHH, 5, YY, ++, ///, \ 
* Comment: Tested using the Spitbol for Linux version of SNOBOL4

	lf = substr(&alphabet,11,1) ;* New line or line feed

* Function split_cc will split a string on a change of character.
	define('split_cc(s)tchar,target,post')
	:(split_cc_end)
split_cc
	tchar = substr(s,1,1) :f(freturn)
	split_cc_pat = span(*tchar) . target (rpos(0) | len(1) . tchar rem) . post
split_cc2
	s ? split_cc_pat = post :f(split_cc3)
	split_cc = (ident(split_cc) target, split_cc ', ' target) :s(split_cc2)
split_cc3
	:(return)
split_cc_end

	test_string = "gHHH5YY++///\"
	output = test_string lf
	split_string = split_cc(test_string)
	output = split_string

END
Output:
gHHH5YY++///\

g, HHH, 5, YY, ++, ///, \

Standard ML

(*
 * Head-Tail implementation of grouping
 *)
fun group'     ac      nil = [ac]
  | group'     nil (y::ys) = group' [y] ys
  | group' (x::ac) (y::ys) = if x=y then group' (y::x::ac) ys else (x::ac) :: group' [y] ys

fun group xs = group' nil xs

fun groupString str = String.concatWith ", " (map implode (group (explode str)))
Output:
- groupString "gHHH5YY++///\\";
val it = "g, HHH, 5, YY, ++, ///, \\" : string

Swift

public extension String {
  func splitOnChanges() -> [String] {
    guard !isEmpty else {
      return []
    }

    var res = [String]()
    var workingChar = first!
    var workingStr = "\(workingChar)"

    for char in dropFirst() {
      if char != workingChar {
        res.append(workingStr)
        workingStr = "\(char)"
        workingChar = char
      } else {
        workingStr += String(char)
      }
    }

    res.append(workingStr)

    return res
  }
}

print("gHHH5YY++///\\".splitOnChanges().joined(separator: ", "))
Output:
g, HHH, 5, YY, ++, ///, \

Tailspin

composer splitEquals
  <reps> <nextReps>*
  rule reps: <'(.)\1*'>
  rule nextReps: <reps> -> \(', ' ! $ ! \)
end splitEquals

'gHHH5YY++///\' -> splitEquals -> !OUT::write
Output:
g, HHH, 5, YY, ++, ///, \

tbas

Translation of: BBC BASIC
SUB SPLITUNIQUE$(s$)
	DIM c$, d$, split$, i%
	c$ = LEFT$(s$, 1)
	split$ = ""
	FOR i% = 1 TO LEN(s$)
	  d$ = MID$(s$, i%, 1)
	  IF d$ <> c$ THEN
		split$ = split$ + ", "
		c$ = d$
	  END IF
	  split$ = split$ + d$
	NEXT
	RETURN split$
END SUB

PRINT SPLITUNIQUE$("gHHH5YY++///\")
END

Tcl

This is most concise with regular expressions. Note well the two steps: it could be achieved in one very clever regexp, but being that clever is usually a bad idea (for both readability and performance, in this case).

set string "gHHH5YY++///\\"

regsub -all {(.)\1*} $string {\0, } string
regsub {, $} $string {} string
puts $string
Output:
g, HHH, 5, YY, ++, ///, \

Transd

The task doesn't state explicitly about the order in which substrings should be displayed. So, here are two variants: one is order-preserving, the other is not order-preserving.

#lang transd

MainModule: {
    s: "gHHH5YY++///\\",
    _start: (λ
        (with res ""
            (for c in (split s "") do
                (if (neq Char(c) (back res)) (+= res ", "))
                (+= res c))
            (textout res))

        (lout "Second variant: ")

        (for v in (values (group-by (split s ""))) do
            (textout (if @idx ", ") (join v "")))
    )
}
Output:
g, HHH, 5, YY, ++, ///, \
Second variant:
++, ///, 5, HHH, YY, \, g

VBA

Option Explicit

Sub Split_string_based_on_change_character()
Dim myArr() As String, T As String

Const STRINPUT As String = "gHHH5YY++///\"
Const SEP As String = ", "
    
    myArr = Split_Special(STRINPUT)
    T = Join(myArr, SEP)
    Debug.Print Left(T, Len(T) - Len(SEP))
End Sub

Function Split_Special(Ch As String) As String()
'return an array of Strings
Dim tb, i&, st As String, cpt As Long, R() As String

    tb = Split(StrConv(Ch, vbUnicode), Chr(0))
    st = tb(LBound(tb))
    ReDim R(cpt)
    R(cpt) = st
    For i = 1 To UBound(tb)
        If tb(i) = st Then
            R(cpt) = R(cpt) & st
        Else
            st = tb(i)
            cpt = cpt + 1
            ReDim Preserve R(cpt)
            R(cpt) = st
        End If
    Next
    Split_Special = R
End Function
Output:
g, HHH, 5, YY, ++, ///, \

Vlang

fn main() {
	println(splitter('gHHH5YY++///\\')) \\ The "\" character needs to be escaped.
}

fn splitter(text string) string {
	mut check := text.substr(0, 1)
	mut new_text, mut temp := '', ''
	for index, _ in text {
		temp = text.substr(index, index + 1)
		if temp != check {
			new_text = new_text + ', '
			check = temp 
		}
		new_text = new_text + temp 
	}
	return new_text
}
Output:
g, HHH, 5, YY, ++, ///, \

Wren

var split = Fn.new { |s|
    if (s.count == 0) return ""
    var res = []
    var last = s[0]
    var curr = last
    for (c in s.skip(1)) {
        if (c == last) {
            curr = curr + c
        } else {
            res.add(curr)
            curr = c
        }
        last = c
    }
    res.add(curr)
    return res.join(", ")
}

var s = "gHHH5YY++///\\" 
System.print(split.call(s))
Output:
g, HHH, 5, YY, ++, ///, \

XLISP

(defun delimit (s)
	(defun delim (old-list new-list current-char)
		(if (null old-list)
			new-list
			(delim (cdr old-list) (append new-list
				(if (not (equal (car old-list) current-char))
					`(#\, #\Space ,(car old-list))
					(cons (car old-list) nil) ) )
			(car old-list) ) ) )
	(list->string (delim (string->list s) '() (car (string->list s)))) )

(display (delimit "gHHH5YY++///\\")) ;; NB. The "\" character needs to be escaped
Output:
g, HHH, 5, YY, ++, ///, \

XPL0

string 0;       \change to zero-terminated convention
char S;
[S:= "gHHH5YY++///\";
while S(0) do
        [ChOut(0, S(0));
        if S(1)#S(0) & S(1)#0 then Text(0, ", ");
        S:= S+1;
        ];
]
Output:
g, HHH, 5, YY, ++, ///, \

Yabasic

sub esplit$(instring$)
	if len(instring$) < 2 return instring$
    ret$ = left$(instring$,1)
    for i = 2 to len(instring$)
	if mid$(instring$,i,1) <> mid$(instring$, i - 1, 1) ret$ = ret$ + ", "
        ret$ = ret$ + mid$(instring$, i, 1)
    next i
   return ret$
end sub

print esplit$("gHHH5YY++///\\")

Z80 Assembly

PrintChar equ &BB5A ;Amstrad CPC BIOS call
Terminator equ 0    ;marks the end of a string
        org &8000

	LD HL,StringA
loop:
	ld a,(HL)		;load a char from (HL)
	cp Terminator	        ;is it the terminator?
	ret z			;if so, exit
	ld e,a			;store this char in E temporarily
	inc hl			;next char
	ld a,(HL)		;get next char
	cp Terminator	        ;is the next char the terminator?
	jp z,StringDone	        ;if so, print E and exit.

	;needed to prevent the last char from getting a comma and space.
	
	dec hl			;go back one so we don't skip any chars
	cp e                    ;does (HL) == (HL+1)?
	
	push af
	ld a,e
	call PrintChar		;either way, print E to screen.
	pop af			;retrieve the results of the last compare.
	
	jr z,SkipComma		;if A=E, no comma or space. Just loop again.
	ld a,','
	call PrintChar
	ld a,' '
	call PrintChar
SkipComma:
	inc hl			;next char
	jp loop			;back to start
StringDone:
	ld a,e			;last character in string is printed here.
	jp PrintChar
	
ReturnToBasic:
	RET
	

StringA:
	byte "gHHH5YY++///\",0
Output:
g, HHH, 5, YY, ++, ///, \

zkl

fcn group(str){
   C,out := str[0],Sink(C);
   foreach c in (str[1,*]){ out.write(if(c==C) c else String(", ",C=c)) }
   out.close();
}
group("gHHH5YY++///\\").println();
Output:
g, HHH, 5, YY, ++, ///, \

ZX Spectrum Basic

 10 LET s$="gHHH5YY++///\"
 20 LET c$=s$(1)
 30 LET n$=c$
 40 FOR i=2 TO LEN s$
 50 IF s$(i)<>c$ THEN LET n$=n$+", "
 60 LET n$=n$+s$(i)
 70 LET c$=s$(i)
 80 NEXT i
 90 PRINT n$
Output:
g, HHH, 5, YY, ++, ///, \