nth and nth0 do not work when the position is a number but the list is
free. Examples (on Ubuntu but MacOS is same I think):
address@hidden:~$ gprolog
GNU Prolog 1.3.2
By Daniel Diaz
Copyright (C) 1999-2009 Daniel Diaz
| ?- nth(1,B,c).
no
| ?- nth0(0,B,c).
no
Working examples:
| ?- nth(A,B,c).
A = 1
B = [c|_] ? ;
A = 2
B = [_,c|_] ? ;
A = 3
B = [_,_,c|_] ?
yes
| ?- nth0(A,B,c).
A = 0
B = [c|_] ?
yes
Cheers
--Jasper
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