how can I pass from DCG in Horn clauses with function \+

Question

I want to translate a grammar rule like this, into a clause

char(C) --> [C], { code_type(C, graph), \+ memberchk(C, "()") }.

but does not work

char(C,In,Out):-
   In=[C|Out],
   code_type(C, graph), 
   \+ memberchk(C, "()").

Answer 1

You can use the expand_term/2 built-in Prolog predicate to expand grammar rule into clauses:

?- expand_term((char(C) --> [C], { code_type(C, graph), \+ memberchk(C, "()") }), Clause).
Clause = (char(C, [C|_G1665], _G1651):- (code_type(C, graph), \+memberchk(C, [40, 41])), _G1651=_G1665).