Exercises from https://www.futurelearn.com/courses/functional-programming-erlang/

patterns.erl

-module(patterns).
-export([exxor/2,exxot/2,exxon/2,efix/2,maxThree/3,howManyEqual/3]).

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

exxot(X,Y) ->
    X == Y.

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

efix(X,Y) ->
    (X == Y) and (X > Y).

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

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

recursion.erl

-module(recursion).
-export([fib/1,pieces/1]).

fib(1) ->
    1;
fib(2) ->
    1;
fib(X) when X > 0 ->
    fib(X-1) + fib(X-2).

pieces(1) -> 
    2;
pieces(X) when X > 0 ->
    pieces(X-1) + X.