{-
File: PracticeAnswers.hs
Desc: some practice stuff for 
basic haskell and functional 
programming concepts
-}


module PracticeAnswers where


{-
Function: myflip
takes a list and reverses every other element
if the list is of odd length it will leave the last element alone
-}

myflip (x:y:xs) = y:x:myflip(xs)
myflip  x = x



{-
Function: removeplace
removes an element in a list at position i
-}

removeplace ([], i) = []
removeplace (x:xs, i) = if i == 1 then removeplace (xs, 0)
                        else x:removeplace(xs, i - 1)

{-
Function: member
takes an element n 
returns true if it is in the list, false if not
-}

member (n, []) = False
member (n, x:xs) = if x == n then True
                        else member(n, xs)


{-
Function: summation
given a list of integers, add them together
must use recursion and not the built in 
function
-}
summation [] = 0
summation (x:xs) = x + summation(xs)

{-
Function: fac
find the factorial of a given integer
-}

fac 0 = 1
fac x = x * fac( x - 1)

{-
Function: addone
given a list of integers, add 1
to each item of the list
-}

add x y =  x + y
addonetoall (x:xs) = map (add 1) (x:xs)

{-
Function: myreverse
return a list of items in reverse order
-}

myreverse :: [a] -> [a]
myreverse (x:[])  = []
myreverse (x:xs) = xs ++ [x]