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I am trying to learn Prolog. I have installed Gnu Prolog 1.4.4 on my Mac. I was directly following the example given in the Gnu Prolog Manual, section 4.2.3, "Consulting a Prolog program," but I am not getting the expected results:

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).
/* Hit Ctl-D here. */
user compiled, 3 lines read - 360 bytes written, 19084 ms

(1 ms) yes
| ?- even(X).
uncaught exception: error(existence_error(procedure,even/1),top_level/0)

I am getting the same (bad) results when I use an external file with my definitions. Any idea what is going wrong? Thanks.

Amittai Aviram
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