strange behaviour of `isearch-forward-regexp'

strange behaviour of `isearch-forward-regexp'

[Paul Pogonyshev]

GNU Emacs 21.3.50.1 (i686-pc-linux-gnu, X toolkit, Xaw3d scroll bars) of 2003-06-24 on localhost.localdomain

While searching for " ?t" regular expression, letter 't' in word
"reset" doesn't match.  This is very strange since searching for
"t?t" and even "^I?t" does match the letter.  Is it "a feature"
or a bug somewhere in Emacs?

Paul Pogonyshev

Re: strange behaviour of `isearch-forward-regexp'

[Kevin Rodgers]

Paul Pogonyshev wrote:

> GNU Emacs 21.3.50.1 (i686-pc-linux-gnu, X toolkit, Xaw3d scroll bars) of 2003-06-24 on localhost.localdomain
> 
> While searching for " ?t" regular expression, letter 't' in word
> "reset" doesn't match.  This is very strange since searching for
> "t?t" and even "^I?t" does match the letter.  Is it "a feature"
> or a bug somewhere in Emacs?


It's a feature, though it doesn't appear to be documented in the Emacs manual:

| search-whitespace-regexp's value is "\\s-+"
|
| Documentation:
| *If non-nil, regular expression to match a sequence of whitespace chars.
| This applies to regular expression incremental search.
| You might want to use something like "[ \t\r\n]+" instead.
| In the Customization buffer, that is `[' followed by a space,
| a tab, a carriage return (control-M), a newline, and `]+'.

You need to type `C-s C-q SPC ? t', or set search-whitespace-regexp to nil.

-- 
<a href="mailto:&lt;kevin.rodgers&#64;ihs.com&gt;">Kevin Rodgers</a>

Re: strange behaviour of `isearch-forward-regexp'

[Paul Pogonyshev]

I wrote:
> While searching for " ?t" regular expression, letter 't' in word
> "reset" doesn't match.  This is very strange since searching for
> "t?t" and even "^I?t" does match the letter.  Is it "a feature"
> or a bug somewhere in Emacs?

Kevin Rodgers wrote:

> It's a feature, though it doesn't appear to be documented in the Emacs manual:
>
> | search-whitespace-regexp's value is "\\s-+"
> |
> | Documentation:
> | *If non-nil, regular expression to match a sequence of whitespace chars.
> | This applies to regular expression incremental search.
> | You might want to use something like "[ \t\r\n]+" instead.
> | In the Customization buffer, that is `[' followed by a space,
> | a tab, a carriage return (control-M), a newline, and `]+'.
>
> You need to type `C-s C-q SPC ? t', or set search-whitespace-regexp to nil.

Wouldn't it solve the problem if `search-whitespacec-regexp' was set
to "\\(\\s-+\\)" by default?  Or would it break something match group
related?

And, btw, i'm not subscribed to the list.  Could you please CC answers
to me?

Paul Pogonyshev