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, ++, ///, \
Ada
<lang 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; </lang>
ALGOL 68
<lang algol68>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</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
ANSI BASIC
<lang ansibasic>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</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
AppleScript
<lang AppleScript>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</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
ARM Assembly
<lang ARM Assembly> /* 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, ++, ///, \
</lang>
AWK
<lang 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)
} </lang>
- 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. <lang freebasic>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$;
NEXT</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
BBC BASIC
<lang bbcbasic>REM >split PRINT FN_split( "gHHH5YY++///\" ) END
DEF FN_split( s$ ) 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$</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
C
<lang 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)); }</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
C#
<lang csharp>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);
}</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
C++
<lang cpp> // 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; }</lang>
- Output:
g, HHH, 5, , )), YY, ++, ,,,, ///, \
Clojure
<lang clojure>(defn print-cchanges [s]
(println (clojure.string/join ", " (map first (re-seq #"(.)\1*" s)))))
(print-cchanges "gHHH5YY++///\\") </lang>
- Output:
g, HHH, 5, YY, ++, ///, \
COBOL
<lang 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.
</lang>
- Output:
Requested string gHHH5YY++///\ g, HHH, 5, YY, ++, ///, \ With spaces and commas gHHH5 ))YY++,,,///\ g, HHH, 5, , )), YY, ++, ,,,, ///, \
Common Lisp
<lang 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++///\\") </lang>
- Output:
g, HHH, 5, YY, ++, ///, \
Doing more work that what's being ask, the following solution builds a list of strings then output it:
<lang lisp>(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++///\\")</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
D
<lang 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();
}</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
Dyalect
<lang dyalect>func String.smartSplit() {
var c var str = "" var last = this.len() - 1
for n in 0..last {
if c && this[n] != c {
str += ", "
}
c = this[n]
str += c
}
str
}
print("gHHH5YY++///\\".smartSplit())</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
EasyLang
<lang>a$ = "gHHH5YY++///\" a$[] = str_split a$ c$ = a$[0] for i range len a$[]
if a$[i] <> c$ b$ &= ", " c$ = a$[i] . b$ &= a$[i]
. print b$</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
Elixir
<lang 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++///\\")</lang>
- Output:
input string: gHHH5YY++///\ output string: g, HHH, 5, YY, ++, ///, \
F#
<lang fsharp>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++///\""")</lang>
- Output:
["g"; "HHH"; "5"; "YY"; "++"; "///"; "\"]
Factor
<lang factor>USE: splitting.monotonic "gHHH5YY++///\\" "aaabbccccdeeff" [ [ = ] monotonic-split ", " join print ] bi@</lang>
- Output:
g, HHH, 5, YY, ++, ///, \ aaa, bb, cccc, d, ee, ff
Forth
<lang Forth>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</lang>
- 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. <lang Fortran> 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</lang>
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, ++, ///, \
Go
Treating "character" as a byte: <lang go>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()
}</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
Haskell
<lang Haskell>import Data.List (group, intercalate)
main :: IO () main = putStrLn $ intercalate ", " (group "gHHH5YY++///\\")</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
IS-BASIC
<lang 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</lang>
J
Solution: <lang j>splitChars=: (1 ,~ 2 ~:/\ ]) <;.2 ] delimitChars=: ', ' joinstring splitChars</lang> Example Usage: <lang j> delimitChars 'gHHH5YY++///\' g, HHH, 5, YY, ++, ///, \</lang>
Java
<lang 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();
}
}</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
JavaScript
ES6
<lang JavaScript>(() => {
// GENERIC FUNCTIONS ------------------------------------------------------
// concat :: a -> [a] | [String] -> String const concat = xs => xs.length > 0 ? (() => { const unit = typeof xs[0] === 'string' ? : []; return unit.concat.apply(unit, xs); })() : [];
// group :: Eq a => [a] -> a const group = xs => groupBy((a, b) => a === b, xs);
// groupBy :: (a -> a -> Bool) -> [a] -> a const groupBy = (f, xs) => { const dct = xs.slice(1) .reduce((a, x) => { const h = a.active.length > 0 ? a.active[0] : undefined, blnGroup = h !== undefined && f(h, x); return { active: blnGroup ? a.active.concat([x]) : [x], sofar: blnGroup ? a.sofar : a.sofar.concat([a.active]) }; }, { active: xs.length > 0 ? [xs[0]] : [], sofar: [] }); return dct.sofar.concat(dct.active.length > 0 ? [dct.active] : []); };
// intercalate :: String -> [a] -> String const intercalate = (s, xs) => xs.join(s);
// map :: (a -> b) -> [a] -> [b] const map = (f, xs) => xs.map(f);
// show :: a -> String
const show = (...x) =>
JSON.stringify.apply(
null, x.length > 1 ? [x[0], null, x[1]] : x
);
// stringChars :: String -> [Char] const stringChars = s => s.split();
// TEST -------------------------------------------------------------------
return show(
intercalate(', ',
map(concat, group(stringChars('gHHH5YY++///\\')))
)
);
// -> "g, HHH, 5, YY, ++, ///, \\"
})();</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
jq
<lang 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], (.[$n:] | runs) end;
"gHHH5YY++///\\" | [runs] | join(", ")</lang>
- Output:
Using the -r ("raw output") command-line option of jq:
g, HHH, 5, YY, ++, ///, \
Jsish
Showing off a little unit testing...
Starting with <lang javascript>#!/usr/bin/env jsish
- 'Split a string based on change of character, in Jsish';
function splitOnChange(str:string):string {
if (str.length < 2) return str;
var last = str[0];
var result = last;
for (var pos = 1; pos < str.length; pos++) {
result += ((last == str[pos]) ? last : ', ' + str[pos]);
last = str[pos];
}
return result;
} provide('splitOnChange', 1.0);
/* literal backslash needs escaping during initial processing */
- splitOnChange('gHHH5YY++///\\');
- splitOnChange('a');
- splitOnChange('ab');
- splitOnChange('aaa');
- splitOnChange('aaaba');
- splitOnChange('gH HH5YY++//,/\\');</lang>
Then
prompt$ jsish -u -update true splitOnChange.jsi Created splitOnChange.jsi
Giving
<lang javascript>#!/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!
- /</lang>
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
<lang julia># v0.6 using IterTools
str = "gHHH5YY++///\\" sep = map(join, groupby(identity, str)) println("string: $str\nseparated: ", join(sep, ", "))</lang>
- Output:
string: gHHH5YY++///\ separated: g, HHH, 5, YY, ++, ///, \
Kotlin
<lang scala>// version 1.0.6
fun splitOnChange(s: String): String {
if (s.length < 2) return s
var t = s.take(1)
for (i in 1 until s.length)
if (t.last() == s[i]) t += s[i]
else t += ", " + s[i]
return t
}
fun main(args: Array<String>) {
val s = """gHHH5YY++///\""" println(splitOnChange(s))
}</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
Lua
Note that the backslash must be quoted as a double backslash as Lua uses C-like escape sequences. <lang Lua>function charSplit (inStr)
local outStr, nextChar = inStr:sub(1, 1)
for pos = 2, #inStr do
nextChar = inStr:sub(pos, pos)
if nextChar ~= outStr:sub(#outStr, #outStr) then
outStr = outStr .. ", "
end
outStr = outStr .. nextChar
end
return outStr
end
print(charSplit("gHHH5YY++///\\"))</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
Alternative: Simply scan difference in reverse order and insert delimiter in place, the loop counter i will not update with length of s. <lang lua>function splitdiff(s)
for i=#s,2,-1 do
if s:sub(i,i)~=s:sub(i-1,i-1) then
s = s:sub(1,i-1)..', '.. s:sub(i,-1)
end
end
return s
end</lang>
M2000 Interpreter
Stack New open a new stack object as current stack, and keep the old one. After the end of block execution old stack get back as current stack. Data statement push to bottom (we read from top, so using data we get a FIFO type). Letter$ pops a string or raise an error if no string found at the top of stack.
<lang M2000 Interpreter> 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++///\" </lang>
Maple
Added an additional backlash to escape the \ character at the end. <lang Maple>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++///\\");</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
Mathematica
The backslash (\) must be escaped with another backslash when defining the string. <lang Mathematica>StringJoin@@Riffle[StringCases["gHHH5YY++///\\", p : (x_) .. -> p], ", "]</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
MiniScript
<lang 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("") </lang>
Modula-2
<lang modula2>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.</lang>
- Output:
g HHH 5 YY ++ /// \
Nim
<lang 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++///\""")</lang>
ooRexx
<lang 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</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
Perl
<lang perl>my $str = 'gHHH5YY++///\\'; $str =~ s/((.)\g{-1}*)/$1, /g; $str =~ s/, $//; # remove trailing , print "$str\n"; </lang>
- Output:
g, HHH, 5, YY, ++, ///, \
Perl 6
<lang perl6>sub group-chars ($str) { $str.comb: / (.) $0* / }
- Testing:
for Q[gHHH5YY++///\], Q[fffn⃗n⃗n⃗»»» ℵℵ☄☄☃☃̂☃🤔🇺🇸🤦♂️👨👩👧👦] -> $string {
put 'Original: ', $string;
put ' Split: ', group-chars($string).join(', ');
}</lang>
- Output:
Original: gHHH5YY++///\ Split: g, HHH, 5, YY, ++, ///, \ Original: fffn⃗n⃗n⃗»»» ℵℵ☄☄☃☃̂☃🤔🇺🇸🤦♂️👨👩👧👦 Split: fff, , n⃗n⃗n⃗, »»», , ℵℵ, ☄☄, ☃, ☃̂, ☃, 🤔, 🇺🇸, 🤦♂️, 👨👩👧👦
The second test-case is to show that Perl 6 works with strings on the Unicode grapheme level, handles whitespace, combiners, and zero width characters up to Unicode Version 9.0, and multi-byte Emoji characters up to Version 4.0 correctly. (Perl 6 provisionally handles Unicode Versions 10.0 and Emoji Version 5.0 but they aren't released yet so aren't officially supported.) 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
Phix
<lang Phix>function split_on_change(string in) string out = ""
if length(in) then
integer prev = in[1]
for i=1 to length(in) do
integer ch = in[i]
if ch!=prev then
out &= ", "
prev = ch
end if
out &= ch
end for
end if
return out
end function
puts(1,split_on_change(`gHHH5YY++///\`))</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
PowerShell
<lang PowerShell> 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 }
$splitString
} </lang> <lang PowerShell> Split-String "gHHH5YY++///\" </lang>
- Output:
g, HHH, 5, YY, ++, ///, \
PureBasic
<lang purebasic>Procedure splitstring(s$)
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</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
Python
Python3.6+
Using [itertools.groupby]. <lang python>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)}')</lang>
- Output:
Input: gHHH5YY++///\ Split: g, HHH, 5, YY, ++, ///, \
Python: Using zip
<lang python>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))</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
Python2
<lang python>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))</lang>
- Output:
when using the default input
input string: gHHH5YY++///\
output string: g, HHH, 5, YY, ++, ///, \
Racket
<lang racket>#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++///\ <
)
", "))</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
REXX
version 1
<lang rexx>/*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. */</lang>
- output when using the default input:
input string: gHHH5YY++///\
output string: g, HHH, 5, YY, ++, ///, \
version 2
<lang rexx>/* 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 </lang> {{out]]
input string: gHHH5YY++///\
output string: g, HHH, 5, YY, ++, ///, \
Ring
<lang 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
</lang> Output:
g, HHH, 5, YY, ++, ///, \
Ruby
<lang 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++///\\")</lang>
- Output:
input string: gHHH5YY++///\ output string: g, HHH, 5, YY, ++, ///, \
Rust
<lang 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));
}</lang>
- Output:
input string: g output string: g input string: output string: input string: gHHH5YY++///\ output string: g, HHH, 5, YY, ++, ///, \
Scala
<lang 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++///\"""))</lang>
- Output:
See it in running in your browser by ScalaFiddle (JavaScript)
or by Scastie (JVM).
<lang Scala> 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(",")) </lang>
- Output:
g,HHH,5,YY,++,///,\
Sed
<lang sed> echo 'gHHH5YY++///\' | sed 's/\(.\)\1*/&, /g;s/, $//' </lang>
Sidef
<lang ruby>func group(str) {
gather {
while (var match = (str =~ /((.)\g{-1}*)/g)) {
take(match[0])
}
}
}
say group(ARGV[0] \\ 'gHHH5YY++///\\').join(', ')</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
Standard ML
<lang sml>(*
* Head-Tail implementation of grouping *)
fun group' ac nil = [ac]
| group' nil (y::ys) = group' [y] ys | group' (x::ac) (y::ys) = if x=y then group' (y::x::ac) ys else (x::ac) :: group' [y] ys
fun group xs = group' nil xs
fun groupString str = String.concatWith ", " (map implode (group (explode str)))</lang>
- Output:
- groupString "gHHH5YY++///\\"; val it = "g, HHH, 5, YY, ++, ///, \\" : string
tbas
<lang basic>SUB SPLITUNIQUE$(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</lang>
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).
<lang Tcl>set string "gHHH5YY++///\\"
regsub -all {(.)\1*} $string {\0, } string regsub {, $} $string {} string puts $string</lang>
VBA
<lang vb> Option Explicit
Sub Split_string_based_on_change_character() Dim myArr() As String, T As String
Const STRINPUT As String = "gHHH5YY++///\" Const SEP As String = ", "
myArr = Split_Special(STRINPUT) T = Join(myArr, SEP) Debug.Print Left(T, Len(T) - Len(SEP))
End Sub
Function Split_Special(Ch As String) As String() 'return an array of Strings Dim tb, i&, st As String, cpt As Long, R() As String
tb = Split(StrConv(Ch, vbUnicode), Chr(0))
st = tb(LBound(tb))
ReDim R(cpt)
R(cpt) = st
For i = 1 To UBound(tb)
If tb(i) = st Then
R(cpt) = R(cpt) & st
Else
st = tb(i)
cpt = cpt + 1
ReDim Preserve R(cpt)
R(cpt) = st
End If
Next
Split_Special = R
End Function </lang>
- Output:
g, HHH, 5, YY, ++, ///, \
XLISP
<lang lisp>(defun delimit (s) (defun delim (old-list new-list current-char) (if (null old-list) new-list (delim (cdr old-list) (append new-list (if (not (equal (car old-list) current-char)) `(#\, #\Space ,(car old-list)) (cons (car old-list) nil) ) ) (car old-list) ) ) ) (list->string (delim (string->list s) '() (car (string->list s)))) )
(display (delimit "gHHH5YY++///\\")) ;; NB. The "\" character needs to be escaped</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
zkl
<lang zkl>fcn group(str){
C,out := str[0],Sink(C);
foreach c in (str[1,*]){ out.write(if(c==C) c else String(", ",C=c)) }
out.close();
} group("gHHH5YY++///\\").println();</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
ZX Spectrum Basic
<lang basic> 10 LET s$="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$(i) 80 NEXT i 90 PRINT n$</lang>
- Output:
g, HHH, 5, YY, ++, ///, \
- String manipulation
- Simple
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