-- Informatics 2A Assignment 1, Nov 2016
-- MH test program 4

-- Fast fibonacci function

ffib' :: Integer -> Integer -> Integer -> Integer ;
ffib' n i j =
        if n==0 then i else if n==1 then j else ffib' (n-1) j (i+j) ;

ffib :: Integer -> Integer ;
ffib n = ffib' n 0 1 ;

-- Test expression: ffib 20
-- Type should be:  Integer
-- Value should be: 6765