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prologprolog-cut

Prolog Cut Query

In Prolog using the cut. Why is the effect of the following query to return the following:

?- !,false.
no

yet this query returns the following: 

?- !;false.
yes
Solution

  • The first query performs an AND on ! (which always returns yes) and false, which always returns no. yes AND no = no.

    In the second query, the ! commits execution to the first branch, that is, !, which always returns yes.