gistfile1.txt

module InvertedReg where

import Control.Monad
import Control.Applicative

import Data.Monoid

data Generator s = Gen { generate :: [s] }

instance Monoid (Generator s) where
    mempty = Gen []

    mappend (Gen ls) (Gen rs) = 
        Gen (zipDiagonallyWith mappend ls rs)

zipDiagonallyWith f ls rs = map (uncurry mappend) (zipDiagonally ls rs)

zipDiagonally ls rs = go 1
  where
    go n = ls