Copyright	Copyright (c) 2010--2015 wren gayle romano
License	BSD
Maintainer	wren@community.haskell.org
Stability	provisional
Portability	Haskell98 + CPP
Safe Haskell	None
Language	Haskell98

Data.Or

Contents

Non-truncating zipping functions

Description

A data type for non-exclusive disjunction. This is helpful for things like a generic merge function on sets/maps which could be union, mutual difference, etc. based on which Or value a function argument returns. Also useful for non-truncating zips (cf. zipOr) and other cases where you sometimes want an Either and sometimes want a pair.

Synopsis

Documentation

data Or a b #

A data type for non-exclusive disjunction.

Constructors

Fst a
Both a b
Snd b

Instances

(Eq b, Eq a) => Eq (Or a b) #
Methods (==) :: Or a b -> Or a b -> Bool # (/=) :: Or a b -> Or a b -> Bool #
(Read b, Read a) => Read (Or a b) #
Methods readsPrec :: Int -> ReadS (Or a b) # readList :: ReadS [Or a b] # readPrec :: ReadPrec (Or a b) # readListPrec :: ReadPrec [Or a b] #
(Show b, Show a) => Show (Or a b) #
Methods showsPrec :: Int -> Or a b -> ShowS # show :: Or a b -> String # showList :: [Or a b] -> ShowS #

elimOr :: (a -> c) -> (a -> b -> c) -> (b -> c) -> Or a b -> c #

Functional eliminator for Or.

eitherOr :: Either a b -> Or a b #

Convert an Either into an Or.

Non-truncating zipping functions

zipOr :: [a] -> [b] -> [Or a b] #

A variant of zip which exhausts both lists, annotating which list the elements came from. It will return zero or more Both, followed by either zero or more Fst or else zero or more Snd.

On GHC this is a "good producer" for list fusion.

zipOrWith :: (Or a b -> c) -> [a] -> [b] -> [c] #

A variant of zipOr with a custom Or-homomorphism.

On GHC this is a "good producer" for list fusion.

zipOrBy :: (Or a b -> c -> c) -> c -> [a] -> [b] -> c #

A variant of zipOr with a custom list-homomorphism.

zipOrWithBy #

Arguments

:: (Or a b -> c)	`Or` homomorphism
-> (c -> d -> d)	list homomorphism, `(:)` part
-> d	list homomorphism, `[]` part
-> [a]
-> [b]
-> d

A variant of zipOr with both a custom Or-homomorphism and a custom list-homomorphism. This is no more powerful than zipOrBy, but it may be more convenient to separate the handling of Or from the handling of (:).