max.erl

-module(max).
-export([maxThree/3, howManyEqual/3, xOr1/2, xOr2/2, xOr3/2, tests/0]).

maxThree(X, Y, Z) -> max(X, max(Y, Z)).

xOr1(X, Y) -> not (X == Y).

xOr2(X, Y) -> X =/= Y.

xOr3(X, Y) -> X == not(Y).

xOr4(X, true) -> X == false;
xOr4(X, false) -> X == true.

howManyEqual(X, X, X) -> 3;
howManyEqual(X, X, _Y) -> 2;
howManyEqual(X, _Y, X) -> 2;
howManyEqual(_Y, X, X) -> 2;
howManyEqual(_X, _Y, _Z) -> 0.

tests() ->
    false = xOr1(false, false),
    true = xOr1(true, false),
    true = xOr1(false, true),
    false = xOr1(true, true),
    false = xOr2(false, false),
    true = xOr2(true, false),
    true = xOr2(false, true),
    false = xOr2(true, true),
    false = xOr3(false, false),
    true = xOr3(true, false),
    true = xOr3(false, true),
    false = xOr3(true, true),
    false = xOr4(false, false),
    true = xOr4(true, false),
    true = xOr4(false, true),
    false = xOr4(true, true),
    0 = howManyEqual(1,2,3),
    2 = howManyEqual(1,1,3),
    2 = howManyEqual(1,3,3),
    3 = howManyEqual(1,1,1),
    pass.