I would like to know if there is a way to write false in SWI Prolog instead of error. The situation is the following:
I have written a prolog program that says if a statement is a formula or not, for example:
?- fmla(or(a,b)). Answer = true
The problem is that if you enter fmla(or(a,ne(b))) prolog will say ERROR since it will try to match ne(b) to my database and it doesn't exist. I would prefer if it said false.
Here is the code just in case you want to check:
neg(F) :- fmla(F).
or(F,G) :- fmla(F), fmla(G).
fmla(F) :- at(F).
fmla(F) :- arg(1, F, A), call(F).
imp(F,G) :- fmla(or(neg(F),G)).
and(F,G) :- fmla(neg(or(neg(F),neg(G)))).
iff(F,G) :- and(imp(F,G),imp(G,F)).
Thank you :P!
PD: in order to simplify the program, the only atomic formulas are a and b.