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thezerobit/prolog peano

Created January 5, 2014 20:54
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Peano relation in Prolog using the CLP(FD) that ships with SWI-Prolog.
Raw
prolog peano
:- use_module(library(clpfd)).
peano(N,z) :- N #= 0.
peano(N,s(PDec)) :-
N #> 0,
N - 1 #= NDec,
peano(NDec, PDec).
% ?- peano(4, Q).
% Q = s(s(s(s(z)))) ;
% false.
% ?- peano(Q, s(s(s(s(z))))).
% Q = 4.
% ?- peano(0, Q).
% Q = z ;
% false.
% ?- peano(Q, z).
% Q = 0.
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