Question

I’m having trouble getting the first float element in a list. What I’ve done so far (completely useless, maybe):

get_float( _, F ) :- float( F ).

get_float( [ First | Rest ], F ) :-
    get_float( Rest, F ).

Gives me this:

some_pred( P ) :-
    get_float( SomeList, FloatNumber ),
    writeln( FloatNumber ). % --> prints a stack position

Answer 1

Try this

get_float([], _).

get_float( [ First | Rest ], F ) :-
    (float(First), F = First);
    get_float( Rest, F ).