:- op(1000,xfy,&).
:- op(1100,xfy,exor).

solve(true):- !.
solve(\+P):- !, \+solve(P).
solve( (P, Q) ) :- !, solve(P), solve(Q).
solve(write(X)):-!,write(X).
solve( P ) :- clause(P, Body), solve(Body).
%Note: the 'write' isn't 'pure' prolog/logic
%Also note that generating solutions (rather than testing) will be... wonky.

%This next one's a bit silly. And, yes, I realize that SWI has a built-in xor.
solve( (P exor Q) ):- !,(solve(P)->A=1;A=0),(solve(Q)->B=1;B=0),1 is A+B.

%Also silly. An 'and' that *isn't* short-circuited!
solve( (P & Q) ):- !,solve(P)->solve(Q);(solve(Q),fail).

%Dummy Facts:
person(earl).
person(moo).
person(mindy).

%So, solve(person(moo)) succeeds,
%    solve(person(foxwell)) fails,
%    solve(person(X)) solves for X.
%
%solve(person(earl),person(mindy)) will NOT succeed,
%however
%solve((person(earl),person(mindy)) *will*!