semigroupoids-6.0.0.1: Semigroupoids: Category sans id
Safe HaskellSafe
LanguageHaskell2010

Semigroupoids.Do

Description

This module re-exports operators from Data.Functor.Apply and Data.Functor.Bind, but under the same names as their Applicative and Monad counterparts. This makes it convenient to use do-notation on a type that is a Bind but not a monad (or an Apply but not an Applicative with ApplicativeDo), either using the QualifiedDo extension or the more traditional RebindableSyntax.

{-# LANGUAGE ApplicativeDo #-}
{-# LANGUAGE QualifiedDo #-}

foo :: Apply f => f a -> f b -> f (a, b)
foo as bs = Semi.do
  a <- as
  b <- bs
  pure (a, b)


bar :: Bind m => (a -> b -> m c) -> m a -> m b -> m c
bar f as bs = Semi.do
  a <- as
  b <- bs
  f a b
Synopsis

Documentation

fmap :: Functor f => (a -> b) -> f a -> f b #

(<*) :: Apply f => f a -> f b -> f a #

Since: 5.3.6

(*>) :: Apply f => f a -> f b -> f b #

Since: 5.3.6

(<*>) :: Apply f => f (a -> b) -> f a -> f b #

Since: 5.3.6

(>>) :: Bind m => m a -> m b -> m b #

Since: 5.3.6

(>>=) :: Bind m => m a -> (a -> m b) -> m b #

Since: 5.3.6

join :: Bind m => m (m a) -> m a #

pure :: Applicative f => a -> f a #

return :: Monad m => a -> m a #

fail :: Plus m => String -> m a #

Important note

This ignores whatever String you give it. It is a bad idea to use fail as a form of labelled error; instead, it should only be defaulted to when a pattern match fails.

Since: 5.3.6