I am pulling my hair out! I have installed gprolog (1.4.4) on my Mac, and I am following (I think) the instructions in the Gnu Prolog manual to the letter, but the interactive environment is not remembering my definitions:
GNU Prolog 1.4.4 (64 bits)
Compiled Sep 26 2016, 00:06:17 with clang
By Daniel Diaz
Copyright (C) 1999-2013 Daniel Diaz
| ?- [user].
compiling user for byte code...
even(0).
even(s(s(X))) :- even(X).
user compiled, 3 lines read - 362 bytes written, 21729 ms
(2 ms) yes
| ?- even(X).
uncaught exception: error(existence_error(procedure,even/1),top_level/0)
| ?-
As you can see from the interactive response, I enter Ctl-D after the second line of my knowledge base input (my only rule). Gprolog says that it has compiled my three lines. Why can't it recognize my query correctly? Thanks!
