[Haskell-cafe] Embedding Perl RegEx in Haskell

Brandon Allbery allbery.b at gmail.com
Thu Aug 18 23:27:07 CEST 2011

On Thu, Aug 18, 2011 at 14:01, C K Kashyap <ckkashyap at gmail.com> wrote:

> *Main> let re = listToSequence [ hello, oneOrMore world, hello ]
> *Main> re
> hello(world)+hello
> I am looking for suggestions on how I could encode the anchors - ^ and $
> and also how I could refer to captures. My goal is to be able to extend the
> idea to create an EDSL that could be used to build Perl tasks - such as
> filters, report generators etc

Why not just go with anchorHead and anchorTail or similar?  And a capture
could simply be

     capture name regularExpression

where name can be an Int or support the newer named capture syntaxes.  I'm
not sure I would bother with fancy symbols; if anything, I might in your
position go back to the old v8 regular expressions (or rather Henry
Spencer's unencumbered reimplementation) and use the symbolic names from
that; they were actually virtual machine opcodes.

(Or even

    capture (Maybe name) regularExpression

and (capture Nothing ...) could represent grouping.  That's certainly how
many actual RE implementations define it.)

Arguably this could be seen as a pointless exercise because I could chose to
> do the scripting in Haskell itself but I have a practical problem that I
> have to deal with clusters that have a little dated version of Linux where I
> could not really build the

(Don't even get me started on Linux backward incompatibility... I spent
years fighting that crap, it's one thing I do not at all miss from my old

brandon s allbery                                      allbery.b at gmail.com
wandering unix systems administrator (available)     (412) 475-9364 vm/sms
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