Safe Haskell	Safe-Inferred
Language	Haskell2010

Data.Functor.Monadic

Description

Helper functions for functors.

These operators are designed to make the interoperation between monadic and pure computations more convenient by allowing them to be chained together without peppering the program with superflouos return statements.

Each function is a pure analogue of a monadic one. The correspondences are as follows:

>$> ~ >>= (bind)
$> ~ >> (throw away left argument)
<$ ~ << (re-exported from Data.Functor)
<$< ~ =<< (same as <$>, but with the precedence of >>=)
>=$> ~ >=> (Kleisli composition)
<$=< ~ <=< (flipped Kleisli composition)

Lastly, |> is left-to-right function composition (flipped version of $).

Synopsis

Documentation

module Data.Functor

(>$>) :: Functor f => f a -> (a -> b) -> f b infixl 1 Source

Flipped fmap for chaining plain functions after a functor in the following way:

readFile '1.txt' >$> lines >$> map length >>= print

lines and map length are non-monadic functions, but peppering them with returns, as pure >>= necessitates, is quite tedious.

In general:

m >>= return . f   is the same as   m >$> f

($>) :: Functor f => f b -> a -> f a infixl 1 Source

Left-associatiative, flipped $>. Corresponds to >>

(<$<) :: Functor f => (a -> b) -> f a -> f b infixr 1 Source

Right-associative infix synonym for fmap.

(>=$>) :: Functor f => (a -> f b) -> (b -> c) -> a -> f c infixl 1 Source

Application of >$> to Kleisli composition >=> Use is analogous to that of >$>, e.g.

 f :: FilePath -> IO ()
 f = (readFile >=$> lines >=$> map length >=> print)

In general:

 m >=$> f   is the same as   m >=> return . f

(<$=<) :: Functor f => (b -> c) -> (a -> f b) -> a -> f c infixr 1 Source

Flipped version of >=$>.

(|>) :: a -> (a -> b) -> b infixl 1 Source

Flipped version of $.