prologsuccessor-arithmetics

how to turn a number from the unit form into an integer in prolog?

I have his code in prolog:

int2term(0,0).
int2term(N,s(T)) :- N>0, M is N-1, int2term(M,T).
int2term(N,p(T)) :- N<0, M is N+1, int2term(M,T).

that shows a number from this form s(s(0)) to this form 2 . I tried to make the reversed version specically 2 -> s(s(0)) using this but nothing : 

term2int(0,0).
term2int(N,T) :- N>0, M is N-1, term2int(M,s(T)).

Any suggestions ?

Solution

  • I have not tested this but it should work:

    term2int(0,0).

term2int(s(T),N) :- term2int(T,N1), N is N1+1.

term2int(p(T),N) :- term2int(T,N1), N is N1-1.

    No need to check if > 0 or otherwise, just use s and p for that case. Also N works as a counter.