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>
C
<lang c>#include <string.h>
- include <malloc.h>
- include <stdio.h>
/* checks if character exists in list */
int contains( char character, char * list ){
while( *list ){
if( character == *list )
return 1;
++ list;
}
return 0;
}
/* removes all chars from string */
char * strip_chars( char * string, char * chars ){
char * newstr = malloc( strlen( string ) ); int counter = 0;
while( *string ){
if( contains( *string, chars ) != 1 ){
newstr[ counter ] = *string;
++ counter;
}
++ string;
}
return newstr;
}
int main( int argc, char ** argv ){
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++
Note: this uses a C++0x lambda function <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!
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>
Go
<lang go>package main
import (
"fmt" "strings"
)
func stripchars(str, chr string) string {
return strings.Map(func(rune int) int {
if strings.IndexRune(chr, rune) < 0 {
return rune
}
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!
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>
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>
Perl
Caveat: in this version hyphens in the second argument can be used to specify ranges; if you need to actually strip hyphens, you need to put a backslash before it <lang perl>sub stripchars {
my ($s, $chars) = @_;
eval("\$s =~ tr/$chars//d;");
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!
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
<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>
Ruby
<lang ruby>>> "She was a soul stripper. She took my heart!".delete("aei") => "Sh ws soul strppr. Sh took my hrt!"</lang>
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
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>