Rule and query Help in prolog

Question

There are facts like :

student(ram, cs). // ram is student of cs branch

student(kiri,it).

student(akshay,cs).

student(sanjay,me).

I want to write a rule to find out the classmates in any branch AND a query to list out students in a branch say cs. Please help.

what query I had to run if i had to find classmates of akshay?

Answer 1

this being a follow up of this previous question, let's keep on the same mood...

classmates(Classmates) :-
  aggregate(set(P), B^Q^(student(P,B), student(Q,B), P\=Q), Classmates).

yields

?- classmates(L).
L = [akshay, ram].

Answer 2

Two students are classmates if they are participating the same course.

classmates(X, Y) :- student(X, A), student(Y, A), X @< Y.

@</2 here is for suppressing duplicates. I.e it is enough to have only (A,B) without (B,A), (A,A) and (B,B).

?- classmates(X, Y).
X = akshay,
Y = ram ;
false.

To list out all students in a branch cs:

?- student(X, cs).
X = ram ;
X = akshay.