test for shy-group "feature"?

test for shy-group "feature"?

[Drew Adams]

Emacs 22 has shy groups for regexps; previous versions did not.

When writing conditional code that tries to work with multiple Emacs
versions, it is usually better to test fboundp, boundp, or featurep, than it
is to test the major version. I couldn't find any function, variable, or
feature associated with this new "feature", shy groups. Is there one that I
might have missed? Thanks.

Re: test for shy-group "feature"?

[Lennart Borgman]

Drew Adams wrote:

>Emacs 22 has shy groups for regexps; previous versions did not.
>
>When writing conditional code that tries to work with multiple Emacs
>versions, it is usually better to test fboundp, boundp, or featurep, than it
>is to test the major version. I couldn't find any function, variable, or
>feature associated with this new "feature", shy groups. Is there one that I
>might have missed? Thanks.
>  
>
My guess is that you will find no updates on the elisp level that are 
tied to shy regexp groups. But I am not sure.

RE: test for shy-group "feature"?

[Drew Adams]

    >Emacs 22 has shy groups for regexps; previous versions did not.
    >
    >When writing conditional code that tries to work with multiple Emacs
    >versions, it is usually better to test fboundp, boundp, or
    >featurep, than it
    >is to test the major version. I couldn't find any function,
    >variable, or
    >feature associated with this new "feature", shy groups. Is
    >there one that I
    >might have missed? Thanks.

    My guess is that you will find no updates on the elisp level that are
    tied to shy regexp groups. But I am not sure.

There are elisp updates (e.g. in regexpt-opt), but I couldn't find any new
function, variable, or feature definitions.

Re: test for shy-group "feature"?

[David Kastrup]

"Drew Adams" <drew.adams@oracle.com> writes:

> Emacs 22 has shy groups for regexps; previous versions did not.

Wrong.

* Lisp changes in Emacs 21.1 (see following page for display-related features)

[...]

** Regular expressions now support intervals \{n,m\} as well as
Perl's shy-groups \(?:...\) and non-greedy *? +? and ?? operators.
Also back-references like \2 are now considered as an error if the
corresponding subgroup does not exist (or is not closed yet).
Previously it would have been silently turned into `2' (ignoring the `\').

> When writing conditional code that tries to work with multiple Emacs
> versions, it is usually better to test fboundp, boundp, or featurep, than it
> is to test the major version. I couldn't find any function, variable, or
> feature associated with this new "feature", shy groups. Is there one that I
> might have missed? Thanks.

(if (string-match "\\(?:\\)" "")
   ...
 ...)

-- 
David Kastrup, Kriemhildstr. 15, 44793 Bochum

RE: test for shy-group "feature"?

[Drew Adams]

    > Emacs 22 has shy groups for regexps; previous versions did not.

    Wrong.

    ** Regular expressions now support intervals \{n,m\} as well as
    Perl's shy-groups \(?:...\) and non-greedy *? +? and ?? operators.
    Also back-references like \2 are now considered as an error if the
    corresponding subgroup does not exist (or is not closed yet).
    Previously it would have been silently turned into `2'
    (ignoring the `\').

I didn't find any reference to "shy" by grepping the source code. Thanks for
looking in News.

    > When writing conditional code that tries to work with multiple Emacs
    > versions, it is usually better to test fboundp, boundp, or
    > featurep, than it
    > is to test the major version. I couldn't find any function,
    > variable, or
    > feature associated with this new "feature", shy groups. Is
    > there one that I
    > might have missed? Thanks.

    (if (string-match "\\(?:\\)" "")
       ...
     ...)

Very good (elegant - it even acts as an explanatory comment).

Thanks.