named choice points

[Thomas Sjöland]

Jorge M. Pelizzoni wrote:

>Hi, all!
>
>In Prolog there is a way to "name" choice points so as to allow cutting
>at once all choice points occurring after a referred choice point. 
>
There is not, as far as I can tell (or perhaps I didn't read the 
fine-print of the Prolog manuals).
A mechanism called "intelligent back-tracking"
 similar to what you refer to was discussed in the literature in the 
beginning of the eighties,
but was never adopted in Prolog, mainly due to interference with the 
non-logical aspects
of logic programming languages. Cut itself is hard enough to
understand and use. Introducing more complex control mechanisms was 
never accepted by
the logic programing community.

Another example from history was "meta-cut" used in addition to the 
ordinary "cut"
in one of IBM's Prolog systems.
I recall also "ancestral cut", perhaps the same operator, or not?

    -Thomas Sjöland, lecturer (for instance in the logic programing course)





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