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Re: 'once' predicate..


From: Henk Vandecasteele
Subject: Re: 'once' predicate..
Date: Tue, 05 Nov 2002 09:52:58 +0100
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.0.1) Gecko/20020823 Netscape/7.0

Dear,

once/1 should behave identical as with the definition:

once(Goal):- call(Goal), !.

or identical

once(Goal):- call(Goal) -> true.

Of course the compiler can optimise the call to once/1 to avoid the
metacall.

You can use the once/1 predicate when you are only interested in the
first solution of a call to a predicate. And thus avoid unnecesary
backtracking.

Regards,

Henk


Abhinav-Bhardwaj wrote:
hi,
can anybody explain what is 'once' predicate, and where it is
most commonly applied ?
thanks and regards,
Abhinav



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