Operand matching

gistfile1.pl

/* End cases, where str is atom or number */
count(Str, Op, 0) :- atom(Str).
count(Str, Op, 0) :- number(Str).

/* Program */
count(Str, Op, R) :- Str =..[A,B,C],
        test(A, Op, R1),
        count(B, Op, R2),
        count(C, Op, R3),
        R is R1 + R2 + R3.

count(Str, Op, R) :- Str =..[A,B],
        count(A, Op, R1),
        count(B, Op, R2),
        R is R1 + R2.

/* Test returns 1 if operand matches; else 0 */
test(Str, Op, R) :- Str = Op, atom(Str), R is 1; R is 0.