Safe Haskell	Safe-Inferred
Language	Haskell2010

Moo (signature^[?])

Description

A module signature for reader-like monads carrying a record-of-functions as environment.

To be useful for writing indefinite code, it should be expanded through "signature merging" to require extra instances for the main monad M (like MonadIO or MonadUnliftIO) and/or the environment type E (like some HasX typeclass).

https://github.com/danidiaz/really-small-backpack-example/tree/master/lesson3-signature-merging

Synopsis

data M :: Type -> Type
data E :: Type
data D :: Type -> Type
liftD :: D x -> M x

Documentation

data M :: Type -> Type #

A reader-like monad.

Instances

Instances details

Monad M #
Instance details Defined in Moo Methods (>>=) :: M a -> (a -> M b) -> M b # (>>) :: M a -> M b -> M b # return :: a -> M a #
Functor M #
Instance details Defined in Moo Methods fmap :: (a -> b) -> M a -> M b # (<$) :: a -> M b -> M a #
Applicative M #
Instance details Defined in Moo Methods pure :: a -> M a # (<>) :: M (a -> b) -> M a -> M b # liftA2 :: (a -> b -> c) -> M a -> M b -> M c # (>) :: M a -> M b -> M b # (<*) :: M a -> M b -> M a #
MonadReader E M #
Instance details Defined in Moo Methods ask :: M E # local :: (E -> E) -> M a -> M a # reader :: (E -> a) -> M a #

data E :: Type #

The monad environment.

Instances

Instances details

MonadReader E M #
Instance details Defined in Moo Methods ask :: M E # local :: (E -> E) -> M a -> M a # reader :: (E -> a) -> M a #

data D :: Type -> Type #

The monad in which the functions in the environment have their effects.

We don't require Functor, Applicative or Monad from D because the plan is to always lift D values to M as soon as they're obtained.

liftD :: D x -> M x #

Lifts an effects from the secondary monad D into M.