The original example in the last section was this:
foo(A, B) :-
\+ (A = B),
A = 1,
B = 2.
foo(1, 2) returns true, so you'd expect f(A, B) to return A=1, B=2. But it returns false.
foo(A,B) fails because \+(A = B) fails, because A = B succeeds. That's because = is not an assignment but a unification, and in the query foo(A,B), A and B are variables, so they always unify.
In fact here I'm not sure whether the author expects = to work as an assignment or an equality. In \+(A = B) they seem to expect it to work as an equality, but in A = 1, B = 2, they seem to expect it to work as an assignment. It is neither.
I appreciate unification is confusing and takes effort to get one's head around, but note that the author is selling a book titled LOGIC FOR PROGR∀MMERS (in small caps) so they should really try to understand what the damn heck this logic programming stuff is all about. The book is $30.
Yes, and then they were horribly confused about why foo(A,B) fails, regardless. They clearly have heard of unification and find it a fascinating concept but have no idea what it means.
Honestly, we don't have to wrap everyone on the internets in a fuzzy warm cocoon of acceptance. Sometimes people talk bullshit. If they're open to learn, that's great, but the author is snarkily dismissing any criticism, so they can stew in their ignorance as far as I am concerned.
Like the OP says, the author didn't bother to RTFM before griping.
In fact here I'm not sure whether the author expects = to work as an assignment or an equality. In \+(A = B) they seem to expect it to work as an equality, but in A = 1, B = 2, they seem to expect it to work as an assignment. It is neither.
I appreciate unification is confusing and takes effort to get one's head around, but note that the author is selling a book titled LOGIC FOR PROGR∀MMERS (in small caps) so they should really try to understand what the damn heck this logic programming stuff is all about. The book is $30.