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class Arrow a =>
ArrowError ex (a :: Type -> Type -> Type) | a -> exarrows Control.Arrow.Operations An arrow type that includes errors (or exceptions). Minimal definition: raise and tryInUnless. TODO: the operations here are inconsistent with other arrow transformers.
class Arrow a =>
ArrowReader r (a :: Type -> Type -> Type) | a -> rarrows Control.Arrow.Operations An arrow type that provides a read-only state (an environment). If you also need to modify the state, use ArrowState.
class Arrow a =>
ArrowState s (a :: Type -> Type -> Type) | a -> sarrows Control.Arrow.Operations An arrow type that provides a modifiable state, based of section 9 of Generalising Monads to Arrows, by John Hughes, Science of Computer Programming 37:67-111, May 2000.
class (Monoid w, Arrow a) =>
ArrowWriter w (a :: Type -> Type -> Type) | a -> warrows Control.Arrow.Operations An arrow type that collects additional output (of some Monoid type).
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arrows Control.Arrow.Transformer Construct a new arrow from an existing one.
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arrows Control.Arrow.Transformer.Error Adding a ErrorArrow to an arrow type, but not necessarily as the outer arrow transformer. Typically a composite arrow type is built by applying a series of arrow transformer to a base arrow (usually either a function arrow or a Kleisli arrow. One can add a transformer to the top of this stack using the lift method of the ArrowTransformer class, or remove a state transformer from the top of the stack using the runError encapsulation operator. The methods of this class add and remove state transformers anywhere in the stack. In the instance
instance Arrow a => ArrowAddError ex (ArrowError ex a) a
they are equivalent to lift and runError respectively. Instances are lifted through other transformers withinstance ArrowAddError ex a a' => ArrowAddError ex (FooArrow a) (FooArrow a')
This could be combined with handle, since the resulting arrow is always the arrow of the handler. Separating them has the advantage of consistency with the other arrows, and might give more helpful type error messages. -
arrows Control.Arrow.Transformer.Reader Adding a ReaderArrow to an arrow type, but not necessarily as the outer arrow transformer. Typically a composite arrow type is built by applying a series of arrow transformer to a base arrow (usually either a function arrow or a Kleisli arrow. One can add a transformer to the top of this stack using the lift method of the ArrowTransformer class, or remove a state transformer from the top of the stack using the runReader encapsulation operator. The methods of this class add and remove state transformers anywhere in the stack. In the instance
instance Arrow a => ArrowAddReader r (ArrowReader r a) a
they are equivalent to lift and runReader respectively. Instances are lifted through other transformers withinstance ArrowAddReader r a a' => ArrowAddReader r (FooArrow a) (FooArrow a')
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arrows Control.Arrow.Transformer.State Adding a StateArrow to an arrow type, but not necessarily as the outer arrow transformer. Typically a composite arrow type is built by applying a series of arrow transformer to a base arrow (usually either a function arrow or a Kleisli arrow. One can add a transformer to the top of this stack using the lift method of the ArrowTransformer class, or remove a state transformer from the top of the stack using the runState encapsulation operator. The methods of this class add and remove state transformers anywhere in the stack. In the instance
instance Arrow a => ArrowAddState s (ArrowState s a) a
they are equivalent to lift and runState respectively. Instances are lifted through other transformers withinstance ArrowAddState s a a' => ArrowAddState s (FooArrow a) (FooArrow a')
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arrows Control.Arrow.Transformer.Stream Adding a StreamArrow to an arrow type, but not necessarily as the outer arrow transformer. Typically a composite arrow type is built by applying a series of arrow transformer to a base arrow (usually either a function arrow or a Kleisli arrow. One can add a transformer to the top of this stack using the lift method of the ArrowTransformer class, or remove a state transformer from the top of the stack using the runStream encapsulation operator. The methods of this class add and remove state transformers anywhere in the stack. In the instance
instance Arrow a => ArrowAddStream (ArrowStream a) a
they are equivalent to lift and runStream respectively. Instances are lifted through other transformers withinstance ArrowAddStream a a' => ArrowAddStream (FooArrow a) (FooArrow a')
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arrows Control.Arrow.Transformer.Writer Adding a WriterArrow to an arrow type, but not necessarily as the outer arrow transformer. Typically a composite arrow type is built by applying a series of arrow transformer to a base arrow (usually either a function arrow or a Kleisli arrow. One can add a transformer to the top of this stack using the lift method of the ArrowTransformer class, or remove a state transformer from the top of the stack using the runWriter encapsulation operator. The methods of this class add and remove state transformers anywhere in the stack. In the instance
instance Arrow a => ArrowAddWriter w (ArrowWriter w a) a
they are equivalent to lift and runWriter respectively. Instances are lifted through other transformers withinstance ArrowAddWriter w a a' => ArrowAddWriter w (FooArrow a) (FooArrow a')