fibandcuts.erl

-module(fibandcuts).
-export([factorial/1, fibonacci/1, pieces/1]).
-export([test_pieces/0,test_fibonacci/0]).
-author("Pradeep Pillai").


%Factorial of N
%1 * 2 * 3 * (N-1)
%Factorial of 0 is 0

factorial(0) -> 
    1;
factorial(N) when N > 0 ->
    N * factorial(N-1).


fibonacci(0) ->
    0;
fibonacci(1) ->
    1;
fibonacci(N) when N > 1 ->
   fibonacci(N - 2) + fibonacci(N - 1).

%when no cuts one piece of paper
%when on cut two piece so 1 + pieces(0) which evaluates to 1 + 1
%when 2 cuts so 2 + piece(1) = 2 + 1 + piece(0) = 2+1+1 = 4
%when 3 cuts so 3 + piece(2) = 3 + 2 + piece(1) = 3 + 2 + 1 + piece(0) = 3 + 2 + 1 + 1 = 7
pieces(0) ->
    1;
pieces(1) ->
    1 + pieces(0);
pieces(N) when N > 0->
    N + pieces(N - 1).



%%tests

test_pieces() ->
    (pieces(0) == 1) andalso (pieces(1) == 2) andalso (pieces(2) == 4).

test_fibonacci() ->
    (fibonacci(0) == 0) andalso (fibonacci(1) == 1) andalso (fibonacci(3) == 2).

Very Good!