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Re: Regular expression search
Re: Regular expression search
Wed, 1 Nov 2006 13:10:59 -0800
thank you for your explanation. The [[:print:]] notation didn't quite work
either, but following your suggestion I tried \\S- and it worked.
(defun vb-first-printable ()
( if (re-search-forward "\\S-" (line-end-position) 't)
Boy, nothing is what it seems with emacs :-)
On Wednesday 01 November 2006 12:04, Kevin Rodgers wrote:
> vb wrote:
> > let's say I need a function to find first printable character on the line
> > where the pointer is. This is what I'm trying to use:
> > (defun vb-first-printable ()
> > (interactive)
> > (let (limit-position)
> > (beginning-of-line)
> > (next-line 1)
> > (setq limit-position (point))
> > (previous-line 1)
> > (re-search-forward "\\S" limit-position 't)))
> > when I try executing this, I get the following error:
> > ====================================================
> > Debugger entered--Lisp error: (invalid-regexp "Premature end of regular
> > expression")
> > re-search-forward("\\S" 3543 t)
> > (let (limit-position) (beginning-of-line) (next-line 1) (setq
> > limit-position (point)) (previous-line 1) (re-search-forward "\\S"
> > limit-position (quote t)))
> > vb-first-printable()
> > call-interactively(vb-first-printable)
> > ===================================================
> > the same problem happens when I try re-search-forward from the command
> > line: if I enter "\S" as the pattern to search, I get "premature end of
> > regular expression" error, but if I enter "\\S" as the regular
> > expression pattern, the only thing it finds is this pattern (\\S) itself
> > (as I try it on the same file where the source code is).
> > What am I missing here?
> Commands that prompt you for a regexp allow you to enter it directly;
> but when calling a Lisp function you have to specify the regexp as a
> string, and in order to represent a backslash within a (double quote-
> delimited) string literal you must double it: "This string has 1
> backslash (here: \\) and 1 double quote (here: \")." And of course
> the `\\' regexp matches the backslash character itself.
> The manual states:
> | `\sC'
> | matches any character whose syntax is C. Here C is a character
> | that designates a particular syntax class: thus, `w' for word
> | constituent, `-' or ` ' for whitespace, `.' for ordinary
> | punctuation, etc. *Note Syntax::.
> | `\SC'
> | matches any character whose syntax is not C.
> So you must specify a syntax class `C', e.g. `w' for word constituent,
> `-' or ` ' for whitespace, `.' for ordinary punctuation, etc.
> But as there is no syntax class for printable or non-printable
> characters, that seems like a dead end. But there is the [:print:]
> character class that you can use in regular expressions.
> And finally, all that limit-position/next-line/point/previous-line stuff
> can be replaced by line-end-position:
> (defun vb-first-printable ()
> (re-search-forward "[[:print:]]" (line-end-position)))