I got problem with quadrating equation implementation in prolog. I know some basics but at same point I can not understand output of swish.swi console. I would appreciate any help or suggestions from your side about my errors.
delta(A, B, C, D):- D is B*B - 4*A*C.
equation(A,B,C,X):- D1<0,delta(A,B,C,D1),X is 0. % or false... but how to retur false there?
equation(A,B,C,X):- D1 =:= 0,delta(A,B,C,D1),X is -B/2*A.
equation(A,B,C,X): D1>0,delta(A,B,C,D1),X is -B-sqrt(D1)/2*A.
equation(A,B,C,X): D1>0,delta(A,B,C,D1),X is -B+sqrt(D1)/2*A.
I am getting two errors there after runnign equation(2, 0, 1, X).
Full stop in clause-body? Cannot redefine ,/2
</2: Arguments are not sufficiently instantiated
about
Arguments are not sufficiently instantiated
you must swap delta/4 and the test. Also, it's better to use if/then/else, to avoid recomputing the result:
equation(A,B,C,X) :-
delta(A,B,C,D1),
( D1 < 0
-> X is 0
; D1 =:= 0
-> X is -B/2*A
; X is -B-sqrt(D1)/2*A
).