Lists with padding

Padme.hs

-- taken from http://stackoverflow.com/questions/21349408/zip-with-default-value-instead-of-dropping-values/21350096#21350096

module Main where

import Control.Applicative
import Data.Traversable
import Data.List

data Padme m = (:-)
  { padded :: [m]
  , padder :: m
  }
  deriving (Show, Eq)

instance Applicative Padme where
  pure = ([] :-)
  (fs :- f) <*> (ss :- s) = zapp fs ss :- f s where
    zapp [] ss = map f ss
    zapp fs [] = map ($ s) fs
    zapp (f : fs) (s : ss) = f s : zapp fs ss

instance Functor Padme where
  fmap = (<*>) . pure

deggar :: [String] -> [String]
deggar = transpose . padded . traverse (:- ' ')