ah.erl

-module(third).
-export([maxThree/3,howManyEqual/3,eXOR/2]).

eXOR(X,Y) when is_boolean(X) andalso is_boolean(Y) ->
    case {X,Y} of
        {Y,X} -> false;
        _ -> true
    end.

maxThree(A,B,C) when is_integer(A) andalso is_integer(B) andalso is_integer(C) ->
    max(max(A,B),C).

howManyEqual(A,B,C) when is_integer(A) andalso is_integer(B) andalso is_integer(C) ->
    case {A,B,C} of
        {_,A,A} -> 3;
        {B,A,_} -> 2;
        {C,_,A} -> 2;
        {_,C,B} -> 2;
        {_,_,_} -> 0
    end.

One thing I notice about function howManyEqual is, the arguments A, B, C don't need to be integers. By taking the guard off this function it could be reused for all kinds of Erlang terms, e.g. tuples, lists, etc. It'll work just fine. :-)

@blogscot oh, yes. Thank you for pointing out, awesome.

You can make howManyEqual without case:

howManyEqual(A, A, A) -> 3;
howManyEqual(_, A, A) -> 2;
howManyEqual(A, _, A) -> 2;
howManyEqual(A, A, _) -> 2;
howManyEqual(_, _, _) -> 0.

@hgisinger Thanks for sharing. I was aware of using functions matching but I felt guilty for defining the same 4+ functions' name.