Problem 03

99 Haskell Problems

Problem 3

(*) Find the K’th element of a list. The first element in the list is number 1.

Example:

* (element-at '(a b c d e) 3)
c

Example in Haskell:

Prelude> elementAt [1,2,3] 2
2
Prelude> elementAt "haskell" 5
'e'

Solution:

elementAt x y = x !! (y - 1)

or

elementAt :: [a] -> Int -> a
elementAt (x:_) 1 = x
elementAt (_:xs) n = elementAt xs (n-1)
elementAt _ _ = error "invalid index"
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