Re: Patch for lookaround assertion in regexp

[Juri Linkov]

> OTOH using something like PCRE would finally fix the currently erroneous
> implementation of classes like [:space:], which now is the same as \s-.
> (And personally I would gladly forgo the syntax categories for standard
> [:classes:], although I imagine the former might be used by the
> font-locking or somewhere... I never felt the need for them.)

`pcrecallout' could help to translate \c and \s to PCRE.

>From `man pcrecallout(3)':

    PCRE provides a feature called "callout", which is a means of
    temporarily passing control to the caller of PCRE in the middle of
    pattern matching. The caller of PCRE provides an external function
    by putting its entry point in the global variable pcre_callout. By
    default, this variable contains NULL, which disables all calling out.

    Within a regular expression, (?C) indicates the points at which the
    external function is to be called. Different callout points can be
    identified by putting a number less than 256 after the letter C.
    For example, this pattern has two callout points:

         (?C1)abc(?C2)def