Running:
/Users/smtlaissezfaire/src/git/adventure_in_prolog (master)$ gprolog
GNU Prolog 1.4.4 (64 bits)
Compiled Sep 18 2017, 19:40:04 with clang
By Daniel Diaz
Copyright (C) 1999-2013 Daniel Diaz
| ?- consult(mortal).
compiling /Users/smtlaissezfaire/src/git/adventure_in_prolog/mortal.pl for byte code...
/Users/smtlaissezfaire/src/git/adventure_in_prolog/mortal.pl compiled, 3 lines read - 426 bytes written, 5 ms
(1 ms) yes
| ?- mortal(socrates).
| ?- X = socrates(X).
cannot display cyclic term for X
yes
| ?- consult(mortal).
compiling /Users/smtlaissezfaire/src/git/adventure_in_prolog/mortal.pl for byte code...
/Users/smtlaissezfaire/src/git/adventure_in_prolog/mortal.pl compiled, 4 lines read - 489 bytes written, 5 ms
yes
| ?- mortal(socrates).
yes
| ?- mortal(plato).
yes
| ?- mortal(foo).
no
| ?- reconsult(
)
.
uncaught exception: error(syntax_error('user_input:9 (char:1) expression expected'),read_term/3)
| ?- write('hello world')
.
hello world
yes
| ?-
| ?- mortal(X).
X = socrates ?
yes
| ?- mortal(X).
X = socrates ? ;
X = plato
yes