Adding a colon as a word boundary for syntax highlighting

Adding a colon as a word boundary for syntax highlighting

[Tim Johnson]

Hi:
I'm using the following regex subexpression:
"\\<\\("
As the left-hand word boundary for syntax highlighting in
a lisp-style programming language.

"\\(" adds the opening parenthesis as a word boundary.

I would like to add the colon (':') as an additional word
boundary character.
The subexpressions:
"\\<\\(:" and "\\<\\(\\:" don't seem to work.
In addition I have the following entry:
(?: . "w") to the syntax table. 
Could someone advise me on how to make this work correctly.

On a related note, I believe that there is an emacs add-on that
allows the user to test elisp regexes, but for the life of me,
I can't remember where to find it.
TIA
Tim

Re: Adding a colon as a word boundary for syntax highlighting

[Johan Bockgård]

Tim Johnson <tim@johnsons-web.com> writes:

> I'm using the following regex subexpression:
> "\\<\\("
> As the left-hand word boundary for syntax highlighting in
> a lisp-style programming language.
>
> "\\(" adds the opening parenthesis as a word boundary.

That doesn't make sense.

> I would like to add the colon (':') as an additional word
> boundary character.
> The subexpressions:
> "\\<\\(:" and "\\<\\(\\:" don't seem to work.
> In addition I have the following entry:
> (?: . "w") to the syntax table. 
> Could someone advise me on how to make this work correctly.

Note that font-lock can use a different syntax table than the mode's
ordinary syntax table.

> On a related note, I believe that there is an emacs add-on that
> allows the user to test elisp regexes, but for the life of me,
> I can't remember where to find it.

M-x re-builder or
regex-tool.el

-- 
Johan Bockgård

Re: Adding a colon as a word boundary for syntax highlighting

[Tim Johnson]

Johan Bockgård wrote:
 
>> "\\(" adds the opening parenthesis as a word boundary.
> 
> That doesn't make sense.
 IOWS, I'm wrong? Is "\\(" a meta character?
 Is it not properly escaped.
 
> M-x re-builder or
> regex-tool.el
Thanks
 

Re: Adding a colon as a word boundary for syntax highlighting

[Stefan Monnier]

> I'm using the following regex subexpression:
> "\\<\\("
> As the left-hand word boundary for syntax highlighting in
> a lisp-style programming language.

> "\\(" adds the opening parenthesis as a word boundary.

No, it doesn't.  "\\(" is a regexp element that marks the beginning of
a sub-regexp.  It needs a closing "\\)" before the regexp is valid.
It does nothing to parenthesis characters.

Emacs doesn't know "word boundary characters".  All it knows is that
some characters are word-constituents and others aren't.  And "\\<" is
a regexp that matches an empty string on the condition that the char on
the left is a non-word-constituent and the char on the right is
a word-constituent.

: by default is not considered as a word-constituent.  I'm not sure what
you mean by "adding a colon as a word boundary".

> On a related note, I believe that there is an emacs add-on that
> allows the user to test elisp regexes, but for the life of me,
> I can't remember where to find it.

M-x regexp-builder (bundled with Emacs-22)?


        Stefan

Re: Adding a colon as a word boundary for syntax highlighting

[Tim Johnson]

Stefan Monnier wrote:

 
> No, it doesn't.  "\\(" is a regexp element that marks the beginning of
> a sub-regexp.  It needs a closing "\\)" before the regexp is valid.
> It does nothing to parenthesis characters.
> 
> Emacs doesn't know "word boundary characters".  All it knows is that
> some characters are word-constituents and others aren't.  And "\\<" is
> a regexp that matches an empty string on the condition that the char on
> the left is a non-word-constituent and the char on the right is
> a word-constituent.
 Thank you for explaining the logic of this. 

> : by default is not considered as a word-constituent.  I'm not sure what
> you mean by "adding a colon as a word boundary".
 Perhaps my thinking should be revised to mean 
  "eliminate ':' as a word constituent"
Regards
Tim
 

Re: Adding a colon as a word boundary for syntax highlighting

[Stefan Monnier]

>  Perhaps my thinking should be revised to mean 
>   "eliminate ':' as a word constituent"

Better would be to describe concretely with an example what you want
to do.


        Stefan

Re: Adding a colon as a word boundary for syntax highlighting

[Tim Johnson]

Stefan Monnier wrote:

>>  Perhaps my thinking should be revised to mean
>>   "eliminate ':' as a word constituent"
> 
> Better would be to describe concretely with an example what you want
> to do.
> 
> 
>         Stefan
:-) I want to highlight "second" as in (second lst)
or "second" as in (std:second lst)

I created an intermediary solution by adding a group
with ":\\(" as the left regex. Works as I want...

The full solution might be something like this (I think,
but haven't combined them and haven't tested)
":\\(\\|\\<\\(" Where the alternatives are 1)empty string
2)colon

Unfortunately, I don't code elisp or elisp regexes for a living
and I tend to forget most of what I've learned from one session to
another.
I believe that your logical explanation put me on the right track.
thanks
----
Tim