hjugement-web/src/Voting/Protocol/Utils.purs

   1 module Voting.Protocol.Utils where
   2
   3 import Control.Applicative (class Applicative, (<$))
   4 import Data.Boolean (otherwise)
   5 import Data.Eq (class Eq, (==), (/=))
   6 import Data.Function (($))
   7 import Data.List (List, (:))
   8 import Data.List as List
   9 import Data.List.Lazy as LL
  10 import Data.Maybe (Maybe(..), maybe)
  11 import Data.Traversable (sequence)
  12 import Data.Unit (Unit)
  13
  14 -- | The 'zipWith3' function takes a function which combines three
  15 -- elements, as well as three lists and returns a list of their point-wise
  16 -- combination, analogous to 'zipWith'.
  17 zipWith3 :: forall a b c d. (a->b->c->d) -> List a->List b->List c->List d
  18 zipWith3 z = go
  19  where
  20   go (a:as) (b:bs) (c:cs) = z a b c : go as bs cs
  21   go _ _ _                = List.Nil
  22
  23 -- | NOTE: check the lengths before applying @f@.
  24 isoZipWith :: forall a b c. (a->b->c) -> List a->List b->Maybe (List c)
  25 isoZipWith f as bs
  26  | List.length as /= List.length bs = Nothing
  27  | otherwise = Just (List.zipWith f as bs)
  28
  29 -- | NOTE: check the lengths before applying @f@.
  30 isoZipWith3 :: forall a b c d. (a->b->c->d) -> List a->List b->List c->Maybe (List d)
  31 isoZipWith3 f as bs cs
  32  | List.length as /= List.length bs = Nothing
  33  | List.length as /= List.length cs = Nothing
  34  | otherwise = Just (zipWith3 f as bs cs)
  35
  36 isoZipWithM :: forall f a b c.
  37  Applicative f =>
  38  f Unit -> (a->b->f c) -> List a->List b->f (List c)
  39 isoZipWithM err f as bs =
  40   maybe (List.Nil <$ err) sequence $
  41     isoZipWith f as bs