THANK YOU! I haven't tested that yet but I think that is exactly what I was looking for there. Might be something to consider adding to pilog.l Seems to be fairly standard in prologs - and useful for creating parsers :-)
Beautiful code, thanks again so much! Cheers, Doug --- On Wed, 7/20/11, Alexander Burger <a...@software-lab.de> wrote: > From: Alexander Burger <a...@software-lab.de> > Subject: Re: pilog and Definite Clause Grammar (DCG) > To: picolisp@software-lab.de > Date: Wednesday, July 20, 2011, 2:20 AM > Hi Doug, > > > What's the best way to handle Definite Clause Grammar > syntax in pilog? > > .. > > So, I'm hoping for some pilog rules or a macro maybe > that can handle > > the --> (or equivalent) of DCG in pilog :-) > > I don't fully understand the context or purpose, but > > http://en.wikipedia.org/wiki/Definite_clause_grammar > > says that "DCG notation is just syntactic sugar for normal > definite > clauses in Prolog". > > So you can write a function 'dcg' which does the necessary > translation. > > I would simply call 'be' here, using 'macro' because 'be' > doesn't > evaluate its arguments (i.e. is a FEXPR): > > (de dcg CL > (macro > (be > ^(if (pair (cadr > CL)) > > (list (car CL) (list (cons (caadr CL) '@A) > '@A)) > > (cons > > (car CL) > > '("@In" "@Out") > > (let Vars > > (make > > (link "@In") > > (for (I . @) (cddr CL) > > (link (pack > "@" I)) ) > > (link "@Out") ) > > (mapcar list > > (cdr CL) > > Vars > > (cdr Vars) ) ) ) ) ) ) ) > > With that, the example in Wikipedia could be written as > > (dcg sentence nounPhrase > verbPhrase) > (dcg nounPhrase det noun) > (dcg verbPhrase verb nounPhrase) > (dcg det [the]) > (dcg det [a]) > (dcg noun [cat]) > (dcg noun [bat]) > (dcg verb [eats]) > > This expands to > > : (rules 'sentence 'nounPhrase > 'verbPhrase 'det 'noun 'verb) > 1 (be sentence ("@In" "@Out") (nounPhrase > "@In" "@1") (verbPhrase "@1" "@Out")) > 1 (be nounPhrase ("@In" "@Out") (det > "@In" "@1") (noun "@1" "@Out")) > 1 (be verbPhrase ("@In" "@Out") (verb > "@In" "@1") (nounPhrase "@1" "@Out")) > 1 (be det ((the . @A) @A)) > 2 (be det ((a . @A) @A)) > 1 (be noun ((cat . @A) @A)) > 2 (be noun ((bat . @A) @A)) > 1 (be verb ((eats . @A) @A)) > -> verb > > Does this help? > > Cheers, > - Alex > -- > UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe > -- UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
