Comparación de lenguajes de programación (funciones de cadena)

APL can use regular expressions directly:

Trim←'^ +| +$'⎕R''

Alternatively, a functional approach combining Boolean masks that filter away leading and trailing spaces:

Trim←{⍵/⍨(∨\∧∘⌽∨\∘⌽)' '≠⍵}

Or reverse and remove leading spaces, twice:

Trim←{(∨\' '≠⍵)/⍵}∘⌽⍣2

In AWK, one can use regular expressions to trim:

ltrim(v)=gsub(/^[ \t]+/,"",v)rtrim(v)=gsub(/[ \t]+$/,"",v)trim(v)=ltrim(v);rtrim(v)

or:

functionltrim(s){sub(/^[ \t]+/,"",s);returns}functionrtrim(s){sub(/[ \t]+$/,"",s);returns}functiontrim(s){returnrtrim(ltrim(s));}

There is no standard trim function in C or C++. Most of the available string libraries^[58] for C contain code which implements trimming, or functions that significantly ease an efficient implementation. The function has also often been called EatWhitespace in some non-standard C libraries.

In C, programmers often combine a ltrim and rtrim to implement trim:

#include<ctype.h>#include<string.h>voidrtrim(char*str){char*s;s=str+strlen(str);while(--s>=str){if(!isspace(*s)){break;}*s=0;}}voidltrim(char*str){size_tn;n=0;while(str[n]&&isspace((unsignedchar)str[n])){n++;}memmove(str,str+n,strlen(str)-n+1);}voidtrim(char*str){rtrim(str);ltrim(str);}

The open source C++ library Boost has several trim variants, including a standard one:^[59]

#include<boost/algorithm/string/trim.hpp>trimmed=boost::algorithm::trim_copy("string");

With boost's function named simply trim the input sequence is modified in-place, and returns no result.

Another open source C++ library Qt, has several trim variants, including a standard one:^[60]

#include<QString>trimmed=s.trimmed();

The Linux kernel also includes a strip function, strstrip(), since 2.6.18-rc1, which trims the string "in place". Since 2.6.33-rc1, the kernel uses strim() instead of strstrip() to avoid false warnings.^[61]

A trim algorithm in Haskell:

importData.Char(isSpace)trim::String->Stringtrim=f.fwheref=reverse.dropWhileisSpace

may be interpreted as follows: f drops the preceding whitespace, and reverses the string. f is then again applied to its own output. The type signature (the second line) is optional.

The trim algorithm in J is a functional description:

trim=.#~[:(+./\*.+./\.)' '&~:

That is: filter (#~) for non-space characters (' '&~:) between leading (+./\) and (*.) trailing (+./\.) spaces.

There is a built-in trim function in JavaScript 1.8.1 (Firefox 3.5 and later), and the ECMAScript 5 standard. In earlier versions it can be added to the String object's prototype as follows:

String.prototype.trim=function(){returnthis.replace(/^\s+/g,"").replace(/\s+$/g,"");};

Perl 5 has no built-in trim function. However, the functionality is commonly achieved using regular expressions.

Example:

$string=~s/^\s+//;# remove leading whitespace$string=~s/\s+$//;# remove trailing whitespace

or:

$string=~s/^\s+|\s+$//g;# remove both leading and trailing whitespace

These examples modify the value of the original variable $string.

Also available for Perl is StripLTSpace in String::Strip from CPAN.

There are, however, two functions that are commonly used to strip whitespace from the end of strings, chomp and chop:

• chop removes the last character from a string and returns it.
• chomp removes the trailing newline character(s) from a string if present. (What constitutes a newline is $INPUT_RECORD_SEPARATOR dependent).

In Raku, the upcoming sister language of Perl, strings have a trim method.

Example:

$string = $string.trim; # remove leading and trailing whitespace$string .= trim; # same thing

The Tclstring command has three relevant subcommands: trim, trimright and trimleft. For each of those commands, an additional argument may be specified: a string that represents a set of characters to remove—the default is whitespace (space, tab, newline, carriage return).

Example of trimming vowels:

setstringonomatopoeia settrimmed[stringtrim$stringaeiou];# result is nomatopsetr_trimmed[stringtrimright$stringaeiou];# result is onomatopsetl_trimmed[stringtrimleft$stringaeiou];# result is nomatopoeia

XSLT includes the function normalize-space(string) which strips leading and trailing whitespace, in addition to replacing any whitespace sequence (including line breaks) with one space.

Example:

<xsl:variablename='trimmed'><xsl:value-ofselect='normalize-space(string)'/></xsl:variable>

XSLT 2.0 includes regular expressions, providing another mechanism to perform string trimming.

Another XSLT technique for trimming is to utilize the XPath 2.0 substring() function.