efficiently checking that all the elements of a (big) list are the same

Question

Problem

Let us suppose that we have a list xs (possibly a very big one), and we want to check that all its elements are the same.

I came up wi

Answer 1

While not very efficient (it will traverse the whole list even if the first two elements don't match), here's a cheeky solution:

import Data.List (group)

allTheSame :: (Eq a) => [a] -> Bool
allTheSame = (== 1) . length . group

Just for fun.