prolog - I'm curious if Logic Programs can do algebra

Question

I read a brief article about Prolog and Logic Programming. I'm curious if Logic Programs can do algebra. Like would you be able to ask what the Variable of X is in the equation 5+X = 7 and get an answer of -2?

Answer 1

All serious Prolog systems provide constraint logic programming over finite domains, called CLP(FD) for short, with which you can solve many such equations easily. For example, with SICStus Prolog, SWI and Yap:

?- use_module(library(clpfd)).
true.

?- 5+X #= 7.
X = 2.

Apparently, the answer is 2 instead of -2. Also check out constraint logic programming over other domains, like the rationals with library(clpq).