Copyright	(c) Andrey Mokhov 2018-2019
License	MIT (see the file LICENSE)
Maintainer	andrey.mokhov@gmail.com
Stability	experimental
Safe Haskell	Safe-Inferred
Language	Haskell2010

Control.Selective.Free

Contents

Free selective functors
Static analysis

Description

This is a library for selective applicative functors, or just selective functors for short, an abstraction between applicative functors and monads, introduced in this paper: https://www.staff.ncl.ac.uk/andrey.mokhov/selective-functors.pdf.

This module defines free selective functors using the ideas from the Sjoerd Visscher's package 'free-functors': https://hackage.haskell.org/package/free-functors-1.0.1/docs/Data-Functor-HFree.html.

Synopsis

newtype Select f a = Select (forall g. Selective g => (forall x. f x -> g x) -> g a)
liftSelect :: f a -> Select f a
getPure :: Select f a -> Maybe a
getEffects :: Functor f => Select f a -> [f ()]
getNecessaryEffects :: Functor f => Select f a -> [f ()]
runSelect :: Selective g => (forall x. f x -> g x) -> Select f a -> g a
foldSelect :: Monoid m => (forall x. f x -> m) -> Select f a -> m

Free selective functors

newtype Select f a Source #

Free selective functors.

Constructors

Select (forall g. Selective g => (forall x. f x -> g x) -> g a)

Instances

Instances details

Applicative (Select f) Source #
Instance details Defined in Control.Selective.Free Methods pure :: a -> Select f a Source # (<>) :: Select f (a -> b) -> Select f a -> Select f b Source # liftA2 :: (a -> b -> c) -> Select f a -> Select f b -> Select f c Source # (>) :: Select f a -> Select f b -> Select f b Source # (<*) :: Select f a -> Select f b -> Select f a Source #
Functor (Select f) Source #
Instance details Defined in Control.Selective.Free Methods fmap :: (a -> b) -> Select f a -> Select f b Source # (<$) :: a -> Select f b -> Select f a Source #
Selective (Select f) Source #
Instance details Defined in Control.Selective.Free Methods select :: Select f (Either a b) -> Select f (a -> b) -> Select f b Source #

liftSelect :: f a -> Select f a Source #

Lift a functor into a free selective computation.

Static analysis

getPure :: Select f a -> Maybe a Source #

Extract the resulting value if there are no necessary effects.

getEffects :: Functor f => Select f a -> [f ()] Source #

Collect all possible effects in the order they appear in a free selective computation.

getNecessaryEffects :: Functor f => Select f a -> [f ()] Source #

Extract all necessary effects in the order they appear in a free selective computation.

runSelect :: Selective g => (forall x. f x -> g x) -> Select f a -> g a Source #

Given a natural transformation from f to g, this gives a canonical natural transformation from Select f to g. Note that here we rely on the fact that g is a lawful selective functor.

foldSelect :: Monoid m => (forall x. f x -> m) -> Select f a -> m Source #

Concatenate all effects of a free selective computation.