Prolog-Interpreter

This is a no bells and whistles prolog implementation (for the moment). Extra-logical and meta-logical predicates are not defined (yes, there is no cut). There are two sugarings for numbers and lists available:

• Numbers get translated into their Peano representations: 5 desugars to s(s(s(s(s(zero))))).
• Lists get translated into pairs: [a,b,c] desgugars to cons(a,cons(b,cons(c,empty))) and [x1,x2|xs] desugars to cons(x1,cons(x2,xs)).

The interpreter comes with a small prelude library of basic list/arithmetic operations that is automatically loaded. The arithmetic operations are very slow but with good reason: they are just regular predicates defined on Peano numbers.

Sample usage

Build with stack build or cabal build and run with stack exec -- prolog sample.pl or cabal run. From just the prelude, we can query:

> gcd(42,216,X)?
{ X = 6 };
no.
> append(X,Y,[a,b,c,d,e]), length(X,N), greater(N,2)?
{ X = [a,b,c], Y = [d,e], N = 3 };
{ X = [a,b,c,d], Y = [e], N = 4 };
{ X = [a,b,c,d,e], Y = [], N = 5 };
no.