vars_and_patterns.erl

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

xOr1(X, Y) when X and Y ->
  false;
xOr1(X, Y) when not(X or Y) ->
  false;
xOr1(_, _) -> true.

xOr2(X, Y) when X == Y ->
  false;
xOr2(_, _) -> true.

xOr3(X, Y) when X =/= Y ->
  true;
xOr3(_, _) -> false.

maxThree(A, B, C) when (A >= B) ->
  if
    A > C -> A;
    true -> C
  end;
maxThree(_, B, C) when (B >= C) -> B;
maxThree(_, _, C) -> C.

howManyEqual(A, A, A) -> 3;
howManyEqual(A, B, C) when (A =/= B) and (B =/= C) and (A =/= C) -> 0;
howManyEqual(_, _, _) -> 2.

vars_and_patterns_test.erl

-module(vars_and_patterns_test).
-include_lib("eunit/include/eunit.hrl").
-import(vars_and_patterns, [xOr1/2, xOr2/2, xOr3/2, maxThree/3, howManyEqual/3]).

xOr1_test() ->
  ?assertEqual(false, xOr1(false, false)),
  ?assertEqual(false, xOr1(true, true)),
  ?assertEqual(true, xOr1(true, false)),
  ?assertEqual(true, xOr1(false, true)).

xOr2_test() ->
  ?assertEqual(false, xOr2(false, false)),
  ?assertEqual(false, xOr2(true, true)),
  ?assertEqual(true, xOr2(true, false)),
  ?assertEqual(true, xOr2(false, true)).

xOr3_test() ->
  ?assertEqual(false, xOr3(false, false)),
  ?assertEqual(false, xOr3(true, true)),
  ?assertEqual(true, xOr3(true, false)),
  ?assertEqual(true, xOr3(false, true)).

maxThree_test() ->
  ?assertEqual(3, maxThree(1, 2, 3)),
  ?assertEqual(2, maxThree(2, 1, 2)),
  ?assertEqual(1, maxThree(1, 1, 1)),
  ?assertEqual(5, maxThree(2, 5, 3)).

howManyEqual_test() ->
  ?assertEqual(0, howManyEqual(1, 2, 3)),
  ?assertEqual(2, howManyEqual(1, 1, 3)),
  ?assertEqual(3, howManyEqual(0, 0, 0)),
  ?assertEqual(2, howManyEqual(1, 3, 3)),
  ?assertEqual(2, howManyEqual(1, 0, 1)).