General length

FoldLength.hs

{-|
General 'length' for any 'Foldable' structure.

> foldLength [undefined, undefined] = 2
-}

module FoldLength (foldLength1, foldLength2) where

import Data.Functor
import qualified Data.Foldable as F

------------------------------------------------------------------------

foldLength1 :: (Num i, F.Foldable t) => t a -> i
foldLength1 = F.foldl' (\z _ -> 1 + z) 0

foldLength2 :: (Functor t, F.Foldable t, Num i) => t a -> i
foldLength2 = F.sum . (1 <$)