a challenging list question on prolog

I am ne开发者_如何学运维w on prolog. Can you help me to solve this problem, please.

exam(math, paul).

exam(phys, paul).

exam(cmpe, sofia).

exam(bio, george).

I want to implement the predicate otherExam(L, N). L is a lesson, and N is the list of all lessons (except L) haved by student of L.

otherExam(math,X). returns [phys]

otherExam(cmpe,X). returns []

otherExam(chem,X). returns false (no such lesson)

otherExam(math,[phys]) returns true

otherExam(X,[phys]). returns math

I haved stucked with this problem. If you help me, I will be very happy :))

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check findall/3 and select/3

findall/3 is used to get all the possible results from a query
for example, findall(X,ancestor(X,paul),L) will find all X such as X is an ancestor of paul and will put them in the list L