Strip a set of characters from a string
You are encouraged to solve this task according to the task description, using any language you may know.
The task is to create a function that strips a set of characters from a string. The function should take two arguments: the first argument being a string to stripped and the second, a string containing the set of characters to be stripped. The returned string should contain the first string, stripped of any characters in the second argument:
<lang pseudocode> print stripchars("She was a soul stripper. She took my heart!","aei") Sh ws soul strppr. Sh took my hrt!</lang>
Ada
<lang Ada>with Ada.Text_IO;
procedure Strip_Characters_From_String is
function Strip(The_String: String; The_Characters: String)
return String is
Keep: array (Character) of Boolean := (others => True);
Result: String(The_String'Range);
Last: Natural := Result'First-1;
begin
for I in The_Characters'Range loop
Keep(The_Characters(I)) := False;
end loop;
for J in The_String'Range loop
if Keep(The_String(J)) then
Last := Last+1;
Result(Last) := The_String(J);
end if;
end loop;
return Result(Result'First .. Last);
end Strip;
S: String := "She was a soul stripper. She took my heart!";
begin -- main
Ada.Text_IO.Put_Line(Strip(S, "aei"));
end Strip_Characters_From_String;</lang>
Output:
> ./strip_characters_from_string Sh ws soul strppr. Sh took my hrt!
ALGOL 68
<lang algol68>#!/usr/local/bin/a68g --script #
PROC strip chars = (STRING mine, ore)STRING: (
STRING out := "";
FOR i FROM LWB mine TO UPB mine DO
IF NOT char in string(mine[i], LOC INT, ore) THEN
out +:= mine[i]
FI
OD;
out[@LWB mine]
);
printf(($gl$,stripchars("She was a soul stripper. She took my heart!","aei")))</lang> Output:
Sh ws soul strppr. Sh took my hrt!
AutoHotkey
<lang AutoHotkey>MsgBox % stripchars("She was a soul stripper. She took my heart!","aei")
StripChars(string, charsToStrip){
Loop Parse, charsToStrip
StringReplace, string, string, % A_LoopField, , All
return string
}</lang> Output:
Sh ws soul strppr. Sh took my hrt!
AWK
<lang AWK>#!/usr/bin/awk -f BEGIN {
x = "She was a soul stripper. She took my heart!"; print x; gsub(/[aei]/,"",x); print x;
}</lang>
Output:
She was a soul stripper. She took my heart! Sh ws soul strppr. Sh took my hrt!
BASIC
<lang qbasic>DECLARE FUNCTION stripchars$(src AS STRING, remove AS STRING)
PRINT stripchars$("She was a soul stripper. She took my heart!", "aei")
FUNCTION stripchars$(src AS STRING, remove AS STRING)
DIM l0 AS LONG, t AS LONG, s AS STRING
s = src
FOR l0 = 1 TO LEN(remove)
DO
t = INSTR(s, MID$(remove, l0, 1))
IF t THEN
s = LEFT$(s, t - 1) + MID$(s, t + 1)
ELSE
EXIT DO
END IF
LOOP
NEXT
stripchars$ = s
END FUNCTION</lang>
Output:
Sh ws soul strppr. Sh took my hrt!
See also: Liberty BASIC, PureBasic
Bracmat
This solution handles Unicode (utf-8) characters. Optimizations are: (1) the chars string is hard-coded into the pattern before the pattern is used in the match expression, (2) the output characters are stacked (cheap) rather than appended (expensive). The result string is obtained by stringizing the stack and reversing. To make multibyte characters survive, they are reversed before being put onto the stack. A problem is that this code is negligent of diacritical marks.
<lang bracmat>( ( strip
= string chars s pat
. !arg:(?string.?chars)
& :?s
&
' ( ?
( %
: [%( utf$!sjt
& ( @($chars:? !sjt ?)
| rev$!sjt !s:?s
)
& ~
)
)
?
)
: (=?pat)
& @(!string:!pat)
| rev$(str$!s)
)
& out
$ (strip$("Аппетит приходит во время еды".веп)
);</lang> Output:
Атит риходит о рмя ды
C
<lang c>#include <string.h>
- include <stdio.h>
- include <stdlib.h>
/* removes all chars from string */
char *strip_chars(char *string, char *chars) {
char * newstr = malloc(strlen(string) + 1); int counter = 0;
for ( ; *string; string++) {
if (!strchr(chars, *string)) {
newstr[ counter ] = *string;
++ counter;
}
}
newstr[counter] = 0; return newstr;
}
int main(void) {
char *new = strip_chars("She was a soul stripper. She took my heart!", "aei");
printf("%s\n", new);
free(new); return 0;
}</lang>
Result:
Sh ws soul strppr. Sh took my hrt!
With table lookup
<lang C>#include <stdio.h>
- include <stdlib.h>
- include <string.h>
char *strip(char * str, char *pat) { /* char replacement is typically done with lookup tables if * the replacement set can be large: it turns O(m n) into * O(m + n). * If same replacement pattern is going to be applied to many * strings, it's better to build a table beforehand and reuse it. * If charset is big like unicode, table needs to be implemented * more efficiently, say using bit field or hash table -- it * all depends on the application. */ int i = 0, tbl[128] = {0}; while (*pat != '\0') tbl[(int)*(pat++)] = 1;
char *ret = malloc(strlen(str)); do { if (!tbl[(int)*str]) ret[i++] = *str; } while (*(str++) != '\0');
/* assuming realloc is efficient and succeeds; if not, we could * do a two-pass, count first, alloc and strip second */ return realloc(ret, i); }
int main() { char * x = strip("She was a soul stripper. She took my heart!", "aei"); printf(x); free(x);
return 0; }</lang>Output same as above.
C++
<lang cpp>#include <algorithm>
- include <iostream>
- include <string>
std::string stripchars(std::string str, const std::string &chars) {
str.erase(
std::remove_if(str.begin(), str.end(), [&](char c){
return chars.find(c) != std::string::npos;
}),
str.end()
);
return str;
}
int main() {
std::cout << stripchars("She was a soul stripper. She took my heart!", "aei") << '\n';
return 0;
}</lang> Output:
Sh ws soul strppr. Sh took my hrt!
C#
<lang C sharp> using System;
public static string RemoveCharactersFromString(string testString, string removeChars) {
char[] charAry = removeChars.ToCharArray();
string returnString = testString;
foreach (char c in charAry)
{
while (returnString.IndexOf(c) > -1)
{
returnString = returnString.Remove(returnString.IndexOf(c), 1);
}
}
return returnString;
} </lang>
Usage: <lang C sharp> using System;
class Program {
static void Main(string[] args)
{
string testString = "She was a soul stripper. She took my heart!";
string removeChars = "aei";
Console.WriteLine(RemoveCharactersFromString(testString, removeChars));
}
} </lang> Output:
Sh ws soul strppr. Sh took my hrt!
Using Regex: <lang C sharp> using System; using System.Text.RegularExpressions;
private static string RegexRemoveCharactersFromString(string testString, string removeChars) {
string pattern = "[" + removeChars + "]"; return Regex.Replace(testString, pattern, "");
}</lang>
Common Lisp
<lang lisp>(defun strip-chars (str chars)
(remove-if (lambda (ch) (find ch chars)) str))
(strip-chars "She was a soul stripper. She took my heart!" "aei")
- => "Sh ws soul strppr. Sh took my hrt!"
</lang>
D
<lang d>import std.stdio, std.string;
void main() {
auto s = "She was a soul stripper. She took my heart!";
auto ss = "Sh ws soul strppr. Sh took my hrt!";
assert(s.removechars("aei") == ss);
}</lang>
Delphi
<lang Delphi>program StripCharacters;
{$APPTYPE CONSOLE}
uses SysUtils;
function StripChars(const aSrc, aCharsToStrip: string): string; var
c: Char;
begin
Result := aSrc; for c in aCharsToStrip do Result := StringReplace(Result, c, , [rfReplaceAll, rfIgnoreCase]);
end;
const
TEST_STRING = 'She was a soul stripper. She took my heart!';
begin
Writeln(TEST_STRING); Writeln(StripChars(TEST_STRING, 'aei'));
end.</lang>
Fortran
<lang Fortran>elemental subroutine strip(string,set)
character(len=*), intent(inout) :: string
character(len=*), intent(in) :: set
integer :: old, new, stride
old = 1; new = 1
do
stride = scan( string( old : ), set )
if ( stride > 0 ) then
string( new : new+stride-2 ) = string( old : old+stride-2 )
old = old+stride
new = new+stride-1
else
string( new : ) = string( old : )
return
end if
end do
end subroutine strip</lang>Note: Since strip is an elemental subroutine, it can be called with arrays of strings as well.
Go
<lang go>package main
import (
"fmt" "strings"
)
func stripchars(str, chr string) string {
return strings.Map(func(r rune) rune {
if strings.IndexRune(chr, r) < 0 {
return r
}
return -1
}, str)
}
func main() {
fmt.Println(stripchars("She was a soul stripper. She took my heart!",
"aei"))
}</lang> Output:
Sh ws soul strppr. Sh took my hrt!
Groovy
Solution: <lang groovy>def stripChars = { string, stripChars ->
def list = string as List list.removeAll(stripChars as List) list.join()
}</lang>
Test: <lang groovy>println (stripChars('She was a soul stripper. She took my heart!', 'aei'))</lang>
Output:
Sh ws soul strppr. Sh took my hrt!
Haskell
I decided to make the string the second argument and the characters the first argument, because it is more likely for someone to partially apply the characters to be stripped (making a function that strips certain characters), than the string. <lang haskell>stripChars :: String -> String -> String stripChars = filter . flip notElem</lang>
testing in GHCI:
> stripChars "aei" "She was a soul stripper. She took my heart!" "Sh ws soul strppr. Sh took my hrt!"
Icon and Unicon
The following works in both languages: <lang unicon>procedure main(A)
cs := \A[1] | 'aei' # argument is set of characters to strip every write(stripChars(!&input, cs)) # strip all input lines
end
procedure stripChars(s,cs)
ns := "" s ? while ns ||:= (not pos(0), tab(upto(cs)|0)) do tab(many(cs))) return ns
end</lang>
Sample runs:
->strip She was a soul stripper. She took my heart! Sh ws soul strppr. Sh took my hrt! Aardvarks are ant eaters. Ardvrks r nt trs. ->strip AEIOUaeiou Aardvarks are ant eaters. rdvrks r nt trs. ->
J
Solution:
The dyadic primitive -. (Less) is probably the simplest way to solve this task.
Example Usage: <lang j> 'She was a soul stripper. She took my heart!' -. 'aei' Sh ws soul strppr. Sh took my hrt!</lang>
Java
<lang Java>class StripChars {
public static String stripChars(String inString, String toStrip) {
return inString.replaceAll("[" + toStrip + "]", "");
}
public static void main(String[] args) {
String sentence = "She was a soul stripper. She took my heart!";
String chars = "aei";
System.out.println("sentence: " + sentence);
System.out.println("to strip: " + chars);
System.out.println("stripped: " + stripChars(sentence, chars));
}
}</lang>
output:
sentence: She was a soul stripper. She took my heart! to strip: aei stripped: Sh ws soul strppr. Sh took my hrt!
JavaScript
<lang JavaScript>function stripchars(string, chars) {
return string.replace(RegExp('['+chars+']','g'), );
}</lang>
Logo
<lang logo>to strip :string :chars
output filter [not substringp ? :chars] :string
end
print strip "She\ was\ a\ soul\ stripper.\ She\ took\ my\ heart! "aei
bye</lang>
output:
Sh ws soul strppr. Sh took my hrt!
Lua
<lang lua>function stripchars( str, chr )
local s = "" for g in str:gmatch( "[^"..chr.."]" ) do s = s .. g end return s
end
print( stripchars( "She was a soul stripper. She took my heart!", "aei" ) )</lang>
Liberty BASIC
<lang lb> Print stripchars$("She was a soul stripper. She took my heart!", "aei", 1) End
Function stripchars$(strip$, chars$, num)
For i = 1 To Len(strip$)
If Mid$(strip$, i, 1) <> Mid$(chars$, num, 1) Then
stripchars$ = (stripchars$ + Mid$(strip$, i, 1))
End If
Next i
If (num <= Len(chars$)) Then stripchars$ = stripchars$(stripchars$, chars$, (num + 1))
End Function
</lang>
Mathematica
<lang Mathematica>stripchars[a_,b_]:=StringReplace[a,(#->"")&/@Characters[b]] stripchars["She was a soul stripper. She took my heart!","aei"] ->Sh ws soul strppr. Sh took my hrt!</lang>
MATLAB / Octave
<lang MATLAB> function str = stripchars(str, charlist)
charlist = unique(charlist);
for k=1:length(charlist)
str(str==charlist(k)) = [];
end;
end; </lang>
>>stripchars('She was a soul stripper. She took my heart!','aei')
ans = Sh ws soul strppr. Sh took my hrt!
Nemerle
<lang Nemerle>StripChars( text : string, remove : string ) : string {
def chuck = Explode(remove); Concat( "", Split(text, chuck))
}</lang>
NetRexx
<lang NetRexx>/* NetRexx */
options replace format comments java crossref savelog symbols
say stripchars("She was a soul stripper. She took my heart!", "aei")
return
method stripchars(haystack, chs) public static
loop c_ = 1 to chs.length needle = chs.substr(c_, 1) haystack = haystack.changestr(needle, ) end c_
return haystack
</lang>
Objective-C
<lang objc>@interface NSString (StripCharacters) - (NSString *) stripCharactersInSet: (NSCharacterSet *) chars; @end
@implementation NSString (StripCharacters) - (NSString *) stripCharactersInSet: (NSCharacterSet *) chars {
return [[self componentsSeparatedByCharactersInSet:chars] componentsJoinedByString:@""];
} @end</lang>
To use: <lang objc> NSString *aString = @"She was a soul stripper. She took my heart!";
NSCharacterSet* chars = [NSCharacterSet characterSetWithCharactersInString:@"aei"];
// Display the NSString. NSLog(@"%@", [aString stripCharactersInSet:chars]);</lang>
OCaml
<lang ocaml>let stripchars s cs =
let len = String.length s in
let res = String.create len in
let rec aux i j =
if i >= len then String.sub res 0 j
else if String.contains cs s.[i] then
aux (succ i) (j)
else begin
res.[j] <- s.[i];
aux (succ i) (succ j)
end
in
aux 0 0</lang>
testing in the toplevel:
# stripchars "She was a soul stripper. She took my heart!" "aei" ;; - : string = "Sh ws soul strppr. Sh took my hrt!"
PARI/GP
GP should not be used for string manipulation. A good solution to this problem would probably involve system("perl -e...
<lang parigp>stripchars(s, bad)={
bad=Set(Vec(Vecsmall(bad))); s=Vecsmall(s); my(v=[]); for(i=1,#s,if(!setsearch(bad,s[i]),v=concat(v,s[i]))); Strchr(v)
}; stripchars("She was a soul stripper. She took my heart!","aei")</lang>
Pascal
See Delphi
Perl
Note: this example uses a regular expression character class. Certain characters, like hyphens and brackets, may need to be escaped. <lang perl>sub stripchars {
my ($s, $chars) = @_; $s =~ s/[$chars]//g; return $s;
}
print stripchars("She was a soul stripper. She took my heart!", "aei"), "\n";</lang> Output:
Sh ws soul strppr. Sh took my hrt!
Another good option for stripping characters is to use the tr/// operator. This option is very efficient when the set of characters to strip is fixed at compile time, because tr/// is specifically designed for transforming and deleting characters. Note that hyphens also have special meaning in this case.
<lang perl>$str =~ tr/aei//d;</lang>
Since the characters used for tr/// must be fixed at compile time, unfortunately, it requires the use of an eval to do this generally for any set of characters provided at runtime:
<lang perl>sub stripchars {
my ($s, $chars) = @_;
eval("\$s =~ tr/$chars//d;");
return $s;
}</lang>
Perl 6
<lang perl6>sub strip_chars ( $s, $chars ) {
return $s.trans( $chars.comb X=> );
}
say strip_chars( 'She was a soul stripper. She took my heart!', 'aei' );</lang>
Output:
Sh ws soul strppr. Sh took my hrt!
PHP
<lang php><?php function stripchars($s, $chars) {
return str_replace(str_split($chars), "", $s);
}
echo stripchars("She was a soul stripper. She took my heart!", "aei"), "\n"; ?></lang> Output:
Sh ws soul strppr. Sh took my hrt!
PicoLisp
<lang PicoLisp>(de strDiff (Str1 Str2)
(pack (diff (chop Str1) (chop Str2))) )</lang>
Output:
: (strDiff "She was a soul stripper. She took my heart!" "aei") -> "Sh ws soul strppr. Sh took my hrt!"
PL/I
<lang PL/I> strip_chars: procedure (text, chars) returns (character (100) varying);
declare text character (*) varying, chars character (*) varying; declare out_text character (100); declare ch character (1); declare (i, j) fixed binary;
j = 0;
do i = 1 to length(text);
ch = substr(text, i, 1);
if index(chars, ch) = 0 then
do; j = j + 1; substr(out_text, j, 1) = ch; end;
end;
return (substr(out_text, 1, j) );
end strip_chars; </lang>
PureBasic
PureBasic uses a single (for ASCII) or a two-byte (for Unicode) null to signal the end of a string. Nulls are thus excluded from the allowable characters to strip as they can't be included in a PureBasic string. <lang PureBasic>Procedure.s stripChars(source.s, charsToStrip.s)
Protected i, *ptrChar.Character, length = Len(source), result.s
*ptrChar = @source
For i = 1 To length
If Not FindString(charsToStrip, Chr(*ptrChar\c))
result + Chr(*ptrChar\c)
EndIf
*ptrChar + SizeOf(Character)
Next
ProcedureReturn result
EndProcedure
If OpenConsole()
PrintN(stripChars("She was a soul stripper. She took my heart!", "aei"))
Print(#CRLF$ + #CRLF$ + "Press ENTER to exit"): Input()
CloseConsole()
EndIf</lang> Sample output:
Sh ws soul strppr. Sh took my hrt!
Python
Not using regular expressions
<lang python>>>> def stripchars(s, chars): ... return s.translate(None, chars) ... >>> stripchars("She was a soul stripper. She took my heart!", "aei") 'Sh ws soul strppr. Sh took my hrt!'</lang>
<lang python>>>> import string >>> def stripchars(s, chars): ... return s.translate(string.maketrans("", ""), chars) ... >>> stripchars("She was a soul stripper. She took my heart!", "aei") 'Sh ws soul strppr. Sh took my hrt!'</lang>
Implemented manually: <lang python>>>> def stripchars(s, chars): ... return "".join(c for c in s if c not in chars) ... >>> stripchars("She was a soul stripper. She took my heart!", "aei") 'Sh ws soul strppr. Sh took my hrt!'</lang>
Using regular expressions
<lang python>>>> import re >>> def stripchars(s, chars): return re.sub('[%s]+' % re.escape(chars), , s)
>>> stripchars("She was a soul stripper. She took my heart!", "aei") 'Sh ws soul strppr. Sh took my hrt!' >>> </lang>
REXX
<lang REXX>/* Rexx */
Do
Say stripchars("She was a soul stripper. She took my heart!", "aei")
Return
End Exit
stripchars:
Procedure
Do
Parse arg haystack, chs
Do c_ = 1 to length(chs) needle = substr(chs, c_, 1) haystack = changestr(needle, haystack, ) End c_
Return haystack
End Exit </lang>
Ruby
<lang ruby>>> "She was a soul stripper. She took my heart!".delete("aei") => "Sh ws soul strppr. Sh took my hrt!"</lang>
Scala
<lang scala>def stripChars(s:String, ch:String)= s filterNot (ch contains _)
stripChars("She was a soul stripper. She took my heart!", "aei") // => Sh ws soul strppr. Sh took my hrt!</lang>
Sed
Using echo and piping it through a sed filter: <lang bash>#!/bin/bash
strip_char() {
echo "$1" | sed "s/[$2]//g"
}
</lang>
Seed7
<lang seed7>$ include "seed7_05.s7i";
const func string: stripchars (in string: mainStri, in string: charList) is func
result
var string: strippedStri is "";
local
var char: ch is ' ';
begin
strippedStri := mainStri;
for ch range charList do
strippedStri := replace(strippedStri, str(ch), "");
end for;
end func;
const proc: main is func
begin
writeln(stripchars("She was a soul stripper. She took my heart!", "aei"));
end func;</lang>
Output:
Sh ws soul strppr. Sh took my hrt!
Standard ML
<lang sml>fun stripchars (string, chars) = let
fun aux c =
if String.isSubstring (str c) chars then
""
else
str c
in
String.translate aux string
end</lang>
testing in the interpreter:
- stripchars ("She was a soul stripper. She took my heart!", "aei") ;
val it = "Sh ws soul strppr. Sh took my hrt!" : string
Alternately: <lang sml>fun stripchars (string, chars) =
String.concat (String.tokens (fn c => String.isSubstring (str c) chars) string)
</lang>
testing in the interpreter:
- stripchars ("She was a soul stripper. She took my heart!", "aei") ;
val it = "Sh ws soul strppr. Sh took my hrt!" : string
Smalltalk
<lang smalltalk> | stripChars | stripChars := [ :string :chars | string reject: [ :c | chars includes: c ] ]. stripChars value: 'She was a soul stripper. She took my heart!' value: 'aei'.
"'Sh ws soul strppr. Sh took my hrt!'" </lang>
Tcl
<lang tcl>proc stripchars {str chars} {
foreach c [split $chars ""] {set str [string map [list $c ""] $str]}
return $str
}
set s "She was a soul stripper. She took my heart!" puts [stripchars $s "aei"]</lang>
UNIX Shell
One would normally do this using the standard tr(1) command:
<lang bash>strip_chars() {
echo "$1" | tr -d "$2"
}</lang>
But it can also be accomplished with bash's built-in parameter expansions:
<lang bash>function strip_chars {
echo "${1//[$2]}"
}</lang>
Test code:
<lang bash> strip_chars "She was a soul stripper. She took my heart!" aei</lang>
Output:
Sh ws soul strppr. Sh took my hrt!
TXR
This solution uses the functions compl-span-str and span-str, which are based directly on the standard C library functions strspn and strcspn (or, rather, their wchar_t counterparts wcsspn and wcscspn).
<lang txr>@(next :args) @arg1 @arg2 @(do (defun strip-chars (str set)
(for ((pieces ()) (str-suffix str))
((not (zerop (length str-suffix))) (cat-str (nreverse pieces) ""))
()
(let* ((len-piece (compl-span-str str-suffix set))
(piece (sub-str str-suffix 0 len-piece))
(suff0 (sub-str str-suffix len-piece nil))
(len-non-piece (span-str suff0 set)))
(push piece pieces)
(set str-suffix (sub-str suff0 len-non-piece nil))))))
@(bind result @(strip-chars arg1 arg2))</lang>
$ ./txr rosetta/strip-chars.txr "she was a soul stripper. she stole my heart." "aei" arg1="she was a soul stripper. she stole my heart." arg2="aei" result="sh ws soul strppr. sh stol my hrt."
Ursala
Normally there's no need to define this operation because it's built in. <lang Ursala>strip = ~&j
- cast %s
test = strip('she was a soul stripper. she took my heart','aei')</lang> output:
'sh ws soul strppr. sh took my hrt'
- Programming Tasks
- String manipulation
- Ada
- ALGOL 68
- AutoHotkey
- AWK
- BASIC
- Bracmat
- C
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- TXR
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- Openscad/Omit