Logic programming in C

Question

I am trying to implement some AI planning algorithms in C, but got stuck with the basic concept :)
Before jumping to the main problem, I tried implementing some small framework that would support propositional logic:

FORMULA f = PROPOSITION(a + 3 > 0);
FORMULA g = PROPOSITION(is_smaller_than(b, c));
f = AND(NOT(f), g);

Now, the problem is that I would like not to evaluate the expressions like 'a + 3 > 0' at the moment of defining the formula, but in some later phase:

bool res = EVALUATE(f);

I guess closures would have been handy in this case, but unfortunately I also like to stick to C99.

Any idea ?
How about extending this to predicate logic ?

The final goal (ideally) would be to build an AI planning library, which can be directly plugged-in to the application, and not to receive the problem as STRIPS program strings.

Thanks

Answer 1

OK,

As commented above I have solved the issue by using a structure with method pointer and data in it. This is the most common way of simulating closures in C.

My implementation is available here: https://github.com/pmilosev/clumsy