Convert peano number s(N) to integer in Prolog

Question

I came across this natural number evaluation of logical numbers in a tutorial and it\'s been giving me some headache:

natural_number(0).
natural_number(s(N))         


        

Answer 1

Here is another solution that works "both ways" using library(clpfd) of SWI, YAP, or SICStus

:- use_module(library(clpfd)).

natsx_int(0, 0).
natsx_int(s(N), I1) :-
   I1 #> 0,
   I2 #= I1 - 1,
   natsx_int(N, I2).