[Gass]

hi,
it is possible to use the only goal project to test clauses like this.

Code: Select all

class predicates
    power1:(real, integer, real).
clauses
power1(A,B,C):-
        bound(A),bound(B),!,
        C=exp(B*ln(A)).
goal
   power1(4,3,D).

It gives me an error at the predicates level
thanks

[Gass]

here a more complicated way to solve the problem:

Code: Select all

implement main
    open core
class predicates
    power1 : (real, integer, real [out]).
clauses
    power1(A, B, C) :-
        bound(A),
        bound(B),
        !,
        C = math::exp(B * math::ln(A)).
clauses
    run() :-
        power1(4, 4, C),
        stdio::write(" c = ", C),
        _ = console::readChar().
end implement main
goal
    console::runUtf8(main::run).

[Harrison Pratt]

I suggest using the [</>] button to format your code display.

Code: Select all

class predicates
    power1 : (real A, integer B, real PowerAB [out]).
clauses
    power1(A, B, C) :-
        C = math::exp(B * math::ln(A)).
 
clauses
    run() :-
        power1(4, 3, D),
        stdio::write("\n", D),
        _ = console::readLine().
 
end implement main
 
goal
    console::runUtf8(main::run).

[Thomas Linder Puls]

Goal mode does not exist any more.

Regarding the calculation itself you should notice the power operator (^):

Code: Select all

clauses
    run() :-
        stdio::writef("Power(4, 3) = %\n", 4 ^ 3).

See also Arithmetic Operators.