bug#13617: 24.2.92; [PATCH] Add strip-string

bug#13617: 24.2.92; [PATCH] Add strip-string

[Leo Liu]

Hello Stefan,

Any objection to adding a general utility function strip-string?

Thanks,
Leo.

diff --git a/lisp/subr.el b/lisp/subr.el
index 72b629d6..afa0b753 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -3683,6 +3683,19 @@ (defun subst-char-in-string (fromchar tochar string &optional inplace)
 	  (aset newstr i tochar)))
     newstr))
 
+(defun strip-string (string &optional leading-chars trailing-chars)
+  "Strip STRING of LEADING-CHARS and TRAILING-CHARS.
+LEADING-CHARS and TRAILING-CHARS defaults to \" \f\t\n\r\v\"."
+  (let ((lchars (if (equal leading-chars "")
+		    ""
+		  (concat "[" (or leading-chars " \f\t\n\r\v") "]*")))
+	(rchars (if (equal trailing-chars "")
+		    ""
+		  (concat "[" (or trailing-chars " \f\t\n\r\v") "]*"))))
+    (string-match (concat "\\`" lchars "\\(\\(?:.\\|\n\\)*?\\)" rchars "\\'")
+		  string)
+    (match-string 1 string)))
+
 (defun replace-regexp-in-string (regexp rep string &optional
 					fixedcase literal subexp start)
   "Replace all matches for REGEXP with REP in STRING.

bug#13617: 24.2.92; [PATCH] Add strip-string

[Andreas Schwab]

Leo Liu <sdl.web@gmail.com> writes:

> +		  (concat "[" (or leading-chars " \f\t\n\r\v") "]*")))

What about characters that are special in [...]?

Andreas.

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"And now for something completely different."

bug#13617: 24.2.92; [PATCH] Add strip-string

[Leo Liu]

On 2013-02-03 16:23 +0800, Andreas Schwab wrote:
> What about characters that are special in [...]?

I am thinking of document how leading-chars and trailing-chars should be
written i.e. should be written as if in a [] regexp but without the
enclosing []. What do you think?

Leo

bug#13617: 24.2.92; [PATCH] Add strip-string

[Andreas Schwab]

You could use the same rules as skip-chars-forward.

Andreas.

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GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

bug#13617: 24.2.92; [PATCH] Add strip-string

[Leo Liu]

On 2013-02-03 16:56 +0800, Andreas Schwab wrote:
> You could use the same rules as skip-chars-forward.

I looked at skip-chars-forward before opening this bug but found it
complicate things by introducing new rules.

In strip-string the idea is to have a default covering 90% of the use
cases:

(strip-string s)        ; strip both
(strip-string s nil "") ; strip leading
(strip-string s "")     ; strip trailing

Refer users to regexp as in (info "(elisp)Regexp Special") for the
remaining 10% use cases.

Regards,
Leo

bug#13617: 24.2.92; [PATCH] Add strip-string

[Leo Liu]

Hello Stefan,

On 2013-02-03 17:40 +0800, Leo Liu wrote:
> I looked at skip-chars-forward before opening this bug but found it
> complicate things by introducing new rules.
>
> In strip-string the idea is to have a default covering 90% of the use
> cases:
>
> (strip-string s)        ; strip both
> (strip-string s nil "") ; strip leading
> (strip-string s "")     ; strip trailing
>
> Refer users to regexp as in (info "(elisp)Regexp Special") for the
> remaining 10% use cases.
>
> Regards,
> Leo

What is your take on this?

BTW, comment-string-strip cannot handle strings with newline in them, is
this an oversight?

Leo

bug#13617: 24.2.92; [PATCH] Add strip-string

[Andreas Röhler]

Am 03.02.2013 10:40, schrieb Leo Liu:
> On 2013-02-03 16:56 +0800, Andreas Schwab wrote:
>> You could use the same rules as skip-chars-forward.
>

+1
> I looked at skip-chars-forward before opening this bug but found it
> complicate things by introducing new rules.
>

Which one?
IMO you may use skip-chars... internally, which is fast and reliable.

> In strip-string the idea is to have a default covering 90% of the use
> cases:
>
> (strip-string s)        ; strip both
> (strip-string s nil "") ; strip leading
> (strip-string s "")     ; strip trailing

Suggest keeping either boolean for not, resp. default,
or a string containing chars overriding the default.

while this is obsolet meanwhile:

http://lists.gnu.org/archive/html/gnu-emacs-sources/2007-01/msg00004.html

Andreas

>
> Refer users to regexp as in (info "(elisp)Regexp Special") for the
> remaining 10% use cases.
>
> Regards,
> Leo
>
>
>
>
>

bug#13617: 24.2.92; [PATCH] Add strip-string

[Lars Ingebrigtsen]

Leo Liu <sdl.web@gmail.com> writes:

> Any objection to adding a general utility function strip-string?

This seems to have been implemented in the meantime as `string-trim'.

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