Pattern matching issues

2011-07-12 Thread Panicz Maciej Godek 
Long time no see!

As we all know, The guile module (ice-9 match) includes an
implementation for a pattern matcher as specified by Andrew K. Wright.
I've recently been reading a book by Peter Norvig, where he came up
with the following notation for what he called "Segment Pattern
Matching" (in Common Lisp):

(pat-match '((?* ?p) need (?* ?x)) '(Mr Hulot and I need a vacation))

 should return ((?P MR HULLOT AND I) (?X A VACATION))

I've been wondering if there is a way to represent this sort of
pattern for the pattern matcher provided by Wright (and Guile).

Regards,
M.

Re: Pattern matching issues

2011-07-12 Thread Ludovic Courtès 
Hello,

Panicz Maciej Godek  skribis:

> (pat-match '((?* ?p) need (?* ?x)) '(Mr Hulot and I need a vacation))
>
>  should return ((?P MR HULLOT AND I) (?X A VACATION))
>
> I've been wondering if there is a way to represent this sort of
> pattern for the pattern matcher provided by Wright (and Guile).

I don’t think so, unfortunately.

That said, I recommend asking Alex Shinn since he’s the author of the
implementation that comes with Guile 2.0 (now maintained as part of
Chibi Scheme [0].)

Thanks,
Ludo’.

[0] 
https://code.google.com/p/chibi-scheme/source/browse/lib/chibi/match/match.scm

Re: Pattern matching issues

2011-07-12 Thread Marco Maggi 
Panicz Maciej Godek wrote:

> I've been  wondering if there  is a way to  represent this
> sort of pattern for the pattern matcher provided by Wright
> (and Guile).

The syntax should be something like:

(match '(Mr Hulot and I need a vacation)
  ((?x ... 'need ?y ...)
   (write (list ?x ?y))
   (newline)))

but at  present multiple ellipses  are not supported  at the
same level  (that is in the  same list or  the same vector).
It is  possible to do  it, but a  policy (greedy/non-greedy)
must  be  adopted  to  solve  ambiguous cases  and  it  gets
complicated.

HTH
-- 
Marco Maggi