-- well, making choices really
-- when writing programs we need to make choices, there are 
-- 3 key ways to do this, the first is pattern matching

-- first we define a function
function1 :: Int->Int
function1 5 = 7
function1 7 = 2
function1 1 = 0
function1 x = x*2

-- this is evaluated in sequence, if the input is 5, then the 
-- output is 7, if 7 then 2, if 1 then 0, otherwise input*2

-- another key feature is the idea of the wildcard, that is
-- parameters we do not care the value of in the pattern match,
-- often used as the last value, as the wildcard matches anything
function2 :: Int->Int
function2 4 = 2
function2 1 = 9
function2 _ = 0

-- This also works fine with more than one paramters
function3 :: Int->Int->Int
function3 5 x = x+2           -- so if the first parameter is 5, then...
function3 y 6 = y
function3 _ _ = 0


-- the other option that are used for more sophisticated forking
-- is the "guard"
function4 :: Int->Int
function4 x | x == 5 = 2
            | (x*3) == 8 = 1
            | y = 0 = 5
            | otherwise = 92
  where
    y = mod x 2

-- finally for very very simple forks we have an if
function5 :: Int->Int
function5 x = if x == 7 then 4 else 2