code: function homomorphism(f) {
      var A = f();
  
      return forAll(_.Int).satisfy(function(a) {
        function g(x) { return x * 2; }
  
        return A.of(g).ap(A.of(a)).isEqual(A.of(g(a)));
      });
    }
docs: /*
  3rd Law: Homomorphism
  'a.of(f).ap(a.of(x))' is equivalent to 'a.of(f(x))'