Bound.Class

This module provides the Bound class, for performing substitution into things that are not necessarily full monad transformers.

Documentation

class Bound t where

Instances of Bound generate left modules over monads.

This means they should satisfy the following laws:

m >>>= return ≡ m
m >>>= (λ x → k x >>= h) ≡ (m >>>= k) >>>= h

This guarantees that a typical Monad instance for an expression type where Bound instances appear will satisfy the Monad laws (see doc/BoundLaws.hs).

If instances of Bound are monad transformers, then m >>>= f ≡ m >>= lift . f implies the above laws, and is in fact the default definition.

This is useful for types like expression lists, case alternatives, schemas, etc. that may not be expressions in their own right, but often contain expressions.

Minimal complete definition

Nothing

Methods

(>>>=) :: Monad f => t f a -> (a -> f c) -> t f c infixl 1

Perform substitution

If t is an instance of MonadTrans and you are compiling on GHC >= 7.4, then this gets the default definition:

m >>>= f = m >>= lift . f

Instances

Bound IdentityT

Bound ListT

Bound MaybeT

Bound (ContT c)

Bound (ReaderT r)

Bound (StateT s)

Error e => Bound (ErrorT e)

Monoid w => Bound (WriterT w)

Bound (Scope b)

Bound (Scope b)

Monoid w => Bound (RWST r w s)

(=<<<) :: (Bound t, Monad f) => (a -> f c) -> t f a -> t f c infixr 1

A flipped version of (>>>=).

(=<<<) = flip (>>>=)