🚀 go-pugleaf

This is a reply to article <358@quintus.UUCP>  (R. O'Keefe)
whose author does not understand why the mentioned metainterpreter does not
work for programs containing metacall if ! does cut outside the scope of call/1;
so, I will show it:

first of all, the metainterpreter does not handle builtinpredicates, so
one has to add a rule like:

	prove(Goal) :-
		builtin(Goal) , ! ,
		call(Goal) .

suppose there are two definitions of rule/4:

	rule(a(X),[],0,[call(X)]) .
	rule(a(X),[],0,[write('not cut away')]) .

and execute the query

	?- prove(a(!)) .

the result is the same is for the program

	a(X) :- call(X) .
	a(X) :- write('not cut away') .
	
	and query ?- a(!) .

only if !/0 does NOT cut outside call/1