Copyright	(c) The University of Glasgow 2001
License	BSD-style (see the file libraries/base/LICENSE)
Maintainer	libraries@haskell.org
Stability	provisional
Portability	portable
Safe Haskell	Safe
Language	Haskell2010

Control.Monad.Instances

Description

Deprecated: This module now contains no instances and will be removed in the future

This module is DEPRECATED and will be removed in the future!

Functor and Monad instances for (->) r and Functor instances for (,) a and Either a.

Synopsis

Documentation

class Functor f where Source

The Functor class is used for types that can be mapped over. Instances of Functor should satisfy the following laws:

fmap id  ==  id
fmap (f . g)  ==  fmap f . fmap g

The instances of Functor for lists, Maybe and IO satisfy these laws.

Minimal complete definition

fmap

Methods

fmap :: (a -> b) -> f a -> f b Source

(<$) :: a -> f b -> f a infixl 4 Source

Replace all locations in the input with the same value. The default definition is fmap . const, but this may be overridden with a more efficient version.

Instances

Functor [] Source
Methods fmap :: (a -> b) -> [a] -> [b] Source (<$) :: a -> [b] -> [a] Source
Functor IO Source
Methods fmap :: (a -> b) -> IO a -> IO b Source (<$) :: a -> IO b -> IO a Source
Functor Maybe Source
Methods fmap :: (a -> b) -> Maybe a -> Maybe b Source (<$) :: a -> Maybe b -> Maybe a Source
Functor ReadP Source
Methods fmap :: (a -> b) -> ReadP a -> ReadP b Source (<$) :: a -> ReadP b -> ReadP a Source
Functor ReadPrec Source
Methods fmap :: (a -> b) -> ReadPrec a -> ReadPrec b Source (<$) :: a -> ReadPrec b -> ReadPrec a Source
Functor Last Source
Methods fmap :: (a -> b) -> Last a -> Last b Source (<$) :: a -> Last b -> Last a Source
Functor First Source
Methods fmap :: (a -> b) -> First a -> First b Source (<$) :: a -> First b -> First a Source
Functor STM Source
Methods fmap :: (a -> b) -> STM a -> STM b Source (<$) :: a -> STM b -> STM a Source
Functor Handler Source
Methods fmap :: (a -> b) -> Handler a -> Handler b Source (<$) :: a -> Handler b -> Handler a Source
Functor ZipList Source
Methods fmap :: (a -> b) -> ZipList a -> ZipList b Source (<$) :: a -> ZipList b -> ZipList a Source
Functor Identity Source
Methods fmap :: (a -> b) -> Identity a -> Identity b Source (<$) :: a -> Identity b -> Identity a Source
Functor ArgDescr Source
Methods fmap :: (a -> b) -> ArgDescr a -> ArgDescr b Source (<$) :: a -> ArgDescr b -> ArgDescr a Source
Functor OptDescr Source
Methods fmap :: (a -> b) -> OptDescr a -> OptDescr b Source (<$) :: a -> OptDescr b -> OptDescr a Source
Functor ArgOrder Source
Methods fmap :: (a -> b) -> ArgOrder a -> ArgOrder b Source (<$) :: a -> ArgOrder b -> ArgOrder a Source
Functor ((->) r) Source
Methods fmap :: (a -> b) -> (->) r a -> (->) r b Source (<$) :: a -> (->) r b -> (->) r a Source
Functor (Either a) Source
Methods fmap :: (b -> c) -> Either a b -> Either a c Source (<$) :: b -> Either a c -> Either a b Source
Functor ((,) a) Source
Methods fmap :: (b -> c) -> (a, b) -> (a, c) Source (<$) :: b -> (a, c) -> (a, b) Source
Functor (ST s) Source
Methods fmap :: (a -> b) -> ST s a -> ST s b Source (<$) :: a -> ST s b -> ST s a Source
Functor (Proxy *) Source
Methods fmap :: (a -> b) -> Proxy * a -> Proxy * b Source (<$) :: a -> Proxy * b -> Proxy * a Source
Arrow a => Functor (ArrowMonad a) Source
Methods fmap :: (b -> c) -> ArrowMonad a b -> ArrowMonad a c Source (<$) :: b -> ArrowMonad a c -> ArrowMonad a b Source
Monad m => Functor (WrappedMonad m) Source
Methods fmap :: (a -> b) -> WrappedMonad m a -> WrappedMonad m b Source (<$) :: a -> WrappedMonad m b -> WrappedMonad m a Source
Functor (Const m) Source
Methods fmap :: (a -> b) -> Const m a -> Const m b Source (<$) :: a -> Const m b -> Const m a Source
Functor (ST s) Source
Methods fmap :: (a -> b) -> ST s a -> ST s b Source (<$) :: a -> ST s b -> ST s a Source
Functor f => Functor (Alt * f) Source
Methods fmap :: (a -> b) -> Alt * f a -> Alt * f b Source (<$) :: a -> Alt * f b -> Alt * f a Source
Arrow a => Functor (WrappedArrow a b) Source
Methods fmap :: (c -> d) -> WrappedArrow a b c -> WrappedArrow a b d Source (<$) :: c -> WrappedArrow a b d -> WrappedArrow a b c Source

class Applicative m => Monad m where Source

The Monad class defines the basic operations over a monad, a concept from a branch of mathematics known as category theory. From the perspective of a Haskell programmer, however, it is best to think of a monad as an abstract datatype of actions. Haskell's do expressions provide a convenient syntax for writing monadic expressions.

Instances of Monad should satisfy the following laws:

```
return a >>= k  =  k a
```
```
m >>= return  =  m
```

m >>= (x -> k x >>= h)  =  (m >>= k) >>= h

Furthermore, the Monad and Applicative operations should relate as follows:

```
pure = return
```
```
(<*>) = ap
```

The above laws imply:

```
fmap f xs  =  xs >>= return . f
```
```
(>>) = (*>)
```

and that pure and (<*>) satisfy the applicative functor laws.

The instances of Monad for lists, Maybe and IO defined in the Prelude satisfy these laws.

Minimal complete definition

(>>=)

Methods

(>>=) :: forall a b. m a -> (a -> m b) -> m b infixl 1 Source

Sequentially compose two actions, passing any value produced by the first as an argument to the second.

(>>) :: forall a b. m a -> m b -> m b infixl 1 Source

Sequentially compose two actions, discarding any value produced by the first, like sequencing operators (such as the semicolon) in imperative languages.

return :: a -> m a Source

Inject a value into the monadic type.

fail :: String -> m a Source

Fail with a message. This operation is not part of the mathematical definition of a monad, but is invoked on pattern-match failure in a do expression.

Instances

Monad [] Source
Methods (>>=) :: [a] -> (a -> [b]) -> [b] Source (>>) :: [a] -> [b] -> [b] Source return :: a -> [a] Source fail :: String -> [a] Source
Monad IO Source
Methods (>>=) :: IO a -> (a -> IO b) -> IO b Source (>>) :: IO a -> IO b -> IO b Source return :: a -> IO a Source fail :: String -> IO a Source
Monad Maybe Source
Methods (>>=) :: Maybe a -> (a -> Maybe b) -> Maybe b Source (>>) :: Maybe a -> Maybe b -> Maybe b Source return :: a -> Maybe a Source fail :: String -> Maybe a Source
Monad ReadP Source
Methods (>>=) :: ReadP a -> (a -> ReadP b) -> ReadP b Source (>>) :: ReadP a -> ReadP b -> ReadP b Source return :: a -> ReadP a Source fail :: String -> ReadP a Source
Monad ReadPrec Source
Methods (>>=) :: ReadPrec a -> (a -> ReadPrec b) -> ReadPrec b Source (>>) :: ReadPrec a -> ReadPrec b -> ReadPrec b Source return :: a -> ReadPrec a Source fail :: String -> ReadPrec a Source
Monad Last Source
Methods (>>=) :: Last a -> (a -> Last b) -> Last b Source (>>) :: Last a -> Last b -> Last b Source return :: a -> Last a Source fail :: String -> Last a Source
Monad First Source
Methods (>>=) :: First a -> (a -> First b) -> First b Source (>>) :: First a -> First b -> First b Source return :: a -> First a Source fail :: String -> First a Source
Monad STM Source
Methods (>>=) :: STM a -> (a -> STM b) -> STM b Source (>>) :: STM a -> STM b -> STM b Source return :: a -> STM a Source fail :: String -> STM a Source
Monad Identity Source
Methods (>>=) :: Identity a -> (a -> Identity b) -> Identity b Source (>>) :: Identity a -> Identity b -> Identity b Source return :: a -> Identity a Source fail :: String -> Identity a Source
Monad ((->) r) Source
Methods (>>=) :: (->) r a -> (a -> (->) r b) -> (->) r b Source (>>) :: (->) r a -> (->) r b -> (->) r b Source return :: a -> (->) r a Source fail :: String -> (->) r a Source
Monad (Either e) Source
Methods (>>=) :: Either e a -> (a -> Either e b) -> Either e b Source (>>) :: Either e a -> Either e b -> Either e b Source return :: a -> Either e a Source fail :: String -> Either e a Source
Monad (ST s) Source
Methods (>>=) :: ST s a -> (a -> ST s b) -> ST s b Source (>>) :: ST s a -> ST s b -> ST s b Source return :: a -> ST s a Source fail :: String -> ST s a Source
Monad (Proxy *) Source
Methods (>>=) :: Proxy * a -> (a -> Proxy * b) -> Proxy * b Source (>>) :: Proxy * a -> Proxy * b -> Proxy * b Source return :: a -> Proxy * a Source fail :: String -> Proxy * a Source
ArrowApply a => Monad (ArrowMonad a) Source
Methods (>>=) :: ArrowMonad a b -> (b -> ArrowMonad a c) -> ArrowMonad a c Source (>>) :: ArrowMonad a b -> ArrowMonad a c -> ArrowMonad a c Source return :: b -> ArrowMonad a b Source fail :: String -> ArrowMonad a b Source
Monad m => Monad (WrappedMonad m) Source
Methods (>>=) :: WrappedMonad m a -> (a -> WrappedMonad m b) -> WrappedMonad m b Source (>>) :: WrappedMonad m a -> WrappedMonad m b -> WrappedMonad m b Source return :: a -> WrappedMonad m a Source fail :: String -> WrappedMonad m a Source
Monad (ST s) Source
Methods (>>=) :: ST s a -> (a -> ST s b) -> ST s b Source (>>) :: ST s a -> ST s b -> ST s b Source return :: a -> ST s a Source fail :: String -> ST s a Source
Monad f => Monad (Alt * f) Source
Methods (>>=) :: Alt * f a -> (a -> Alt * f b) -> Alt * f b Source (>>) :: Alt * f a -> Alt * f b -> Alt * f b Source return :: a -> Alt * f a Source fail :: String -> Alt * f a Source