Hello all,

I have experimented a bit with custom syntax for regular expression
matching. My goal was to implement some high-level constructs on top
of a low-level regexp library such as PCRE. The result of my (modest)
experiment is attached. It is a camlp4 grammar extension, which allows
writing

  extract x, y, ... matching e against r in e'

The semantics is as follows. The expression e is evaluated, yielding
a string which is matched against the regular expression r. r must be
either a constant string, or a compiled regular expression; if the
former, pre-compilation code is inserted transparently. The variables
x, y, ... etc. are then bound to the appropriate groups (i.e. x is
bound to the sub-string which matched the whole pattern, y is bound
to the sub-string which matched the first group, etc.) and can be
referred to within e'. Wildcards _ can be used instead of variables.

This is of course pretty modest, but it seems that, with a small
number of such constructs, O'Caml could be turned into a rather nice
textual manipulation language. (Something often requested on this
list.) Opinions and further suggestions are welcome.

-- 
François Pottier
Francois.Pottier@inria.fr
http://pauillac.inria.fr/~fpottier/

Here's how to use the syntax extension:

1. Compile it:

  ocamlc -pp "camlp4o -I `camlp4o -where`" -I `camlp4o -where` -c pcreg.ml

2. At the beginning of your source files, insert

  #load "pcreg.cmo";;

3. Compile your source files using the following option:

  -pp "camlp4o -I ."

   (in addition to any options necessary to include the PCRE library,
    e.g. -I +contrib).