prolog - reversible "binary to number" predicate

Question

What is the best way to convert binary bits (it might be a list of 0/1, for example) into numbers in a reversible way. I've written a native predicate in swi, but is there better solution ? Best regards

Answer 1

Use CLP(FD) constraints, for example:

:- use_module(library(clpfd)).

binary_number(Bs0, N) :-
        reverse(Bs0, Bs),
        foldl(binary_number_, Bs, 0-0, _-N).

binary_number_(B, I0-N0, I-N) :-
        B in 0..1,
        N #= N0 + B*2^I0,
        I #= I0 + 1.

Example queries:

?- binary_number([1,0,1], N).
N = 5.

?- binary_number(Bs, 5).
Bs = [1, 0, 1] .

?- binary_number(Bs, N).
Bs = [],
N = 0 ;
Bs = [N],
N in 0..1 ;
etc.