Summary Programming Fundamentals Functions Cheat Sheet — Haskell Function Reference & Exercises

, 1) Find the last element
of a list without
using last

last' ::
(a) - a last" : (a) - a


last' [] = error 'erro' last" [] + error


last'[x] = last"(x) = x


last' (x: xs) = last' as last" = .
head reverse




2) last but one element of the list

but Last :: (a] -
a butlast' : [a] - a


but Last [b ,
-j =
b but Last' = reverses !!

but Last (- : (s) =
butLast as




3) kth element
of a list but the first element is 1.




kthFromone :: (a] - Int-a

kthFromone list k = list !! (k 1) -




4) Product a list of numbers


myProd Num :: a = (a] - a
my
Prod' Num : a => [a] -a



myProd[] 1 =
myRod' 5] =
1


myProd (x : (s) = x
*
(myProd(s) myProd' (x xs) : = ( *) x (myProd'xs)

5) Produces a list
of the first n integrer that are squares

squareUpto :: Int- (Int] SquareUpto' :: Int- [Int]
squareupto n =
(x 2(x =
(1 ... n]] squareupton = take n[x 2)x =
(1 ...
3]

6) produces a list
of ist - squars and smaller than a
given value


squareSmaller :: Int- (Int]
squarsmalle n =
[y) y
=
SquaresUpton ,
y< n]

7) function that splits an
even-length list into two halves

halve :· (a) +
((a) (a]) ,



halve xs -
(take n Xs , drop n xs)
where 'div'2
n =
length as




5) function that uturn third element in a list

third :: [a) - a third' : [a] + a third" :: [a] - a


third <S = head (tail (tail(s) third'us =s !! 2 third") - : - : -) =

↳ third-head .tail tail .