{-# OPTIONS_GHC -fno-warn-orphans #-}
{-
Copyright (C) 2018 Dr. Alistair Ward
This file is part of BishBosh.
BishBosh is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
BishBosh is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with BishBosh. If not, see .
-}
{- |
[@AUTHOR@] Dr. Alistair Ward
[@DESCRIPTION@] Defines a /pickler/ for 'Either'.
-}
module BishBosh.Data.Either(
-- * Functions
xpickle
) where
import qualified Text.XML.HXT.Arrow.Pickle as HXT
instance (HXT.XmlPickler l, HXT.XmlPickler r) => HXT.XmlPickler (Either l r) where
xpickle = xpickle HXT.xpickle HXT.xpickle
-- | Pickler for an arbitrary datum of type 'Either'.
xpickle :: HXT.PU l -> HXT.PU r -> HXT.PU (Either l r)
xpickle lPickler rPickler = HXT.xpAlt (
const 0 `either` const 1 -- Index into the subsequent pickler-list.
) [
HXT.xpWrap (
Left, -- Construct.
\(Left l) -> l -- Deconstruct.
) lPickler,
HXT.xpWrap (
Right, -- Construct.
\(Right r) -> r -- Deconstruct.
) rPickler
]