Safe Haskell | Safe-Inferred |
---|
The ArrowList
type class, and a collection of list arrow related functions.
This typeclass can be used to embed functions producing multiple outputs into a
an arrow.
- class Arrow ar => ArrowList ar where
- unlist :: ArrowList ar => [b] `ar` b
- unite :: ArrowList ar => (a `ar` (b, b)) -> a `ar` b
- none :: ArrowList ar => a `ar` b
- concatA :: ArrowPlus ar => [a `ar` b] -> a `ar` b
- list :: ArrowList ar => (a `ar` b) -> a `ar` [b]
- empty :: ArrowList ar => (a `ar` b) -> a `ar` Bool
- isA :: ArrowList ar => (a -> Bool) -> a `ar` a
- ifA :: (ArrowList ar, ArrowChoice ar) => (a `ar` c) -> (a `ar` b) -> (a `ar` b) -> a `ar` b
- when :: (ArrowList ar, ArrowChoice ar) => (a `ar` a) -> (a `ar` b) -> a `ar` a
- guards :: (ArrowList ar, ArrowChoice ar) => (a `ar` c) -> (a `ar` b) -> a `ar` b
- filterA :: (ArrowChoice ar, ArrowList ar) => (a `ar` c) -> a `ar` a
- notA :: (ArrowList ar, ArrowChoice ar) => (a `ar` c) -> a `ar` a
- orElse :: (ArrowList ar, ArrowChoice ar) => (a `ar` b) -> (a `ar` b) -> a `ar` b
- maybeL :: ArrowList ar => Maybe a `ar` a
- optional :: (ArrowChoice ar, ArrowList ar) => (a `ar` b) -> a `ar` Maybe b
ArrowList type class.
class Arrow ar => ArrowList ar whereSource
The ArrowList
class represents two possible actions:
- Lifting functions from one value to a list of values into a list arrow.
- Mapping a function over the result list of a list arrow.
(Arrow (ListTArrow m), Monad m) => ArrowList (ListTArrow m) |
Creating list arrows.
unite :: ArrowList ar => (a `ar` (b, b)) -> a `ar` bSource
Take the output of an arrow producing two results and concatenate them into the result of the list arrow.
concatA :: ArrowPlus ar => [a `ar` b] -> a `ar` bSource
Collect the results of applying multiple arrows to the same input.
Collecting the results.
list :: ArrowList ar => (a `ar` b) -> a `ar` [b]Source
Collect the entire results of an list arrow as a singleton value in the result list.
empty :: ArrowList ar => (a `ar` b) -> a `ar` BoolSource
Returns a Bool
indicating whether the input arrow produce any results.
Conditional and filter arrows.
:: (ArrowList ar, ArrowChoice ar) | |
=> (a `ar` c) | Arrow used as condition. |
-> (a `ar` b) | Arrow to use when condition has results. |
-> (a `ar` b) | Arrow to use when condition has no results. |
-> a `ar` b |
Use the result a list arrow as a conditional, like an if-then-else arrow. When the first arrow produces any results the then arrow will be used, when the first arrow produces no results the else arrow will be used.
:: (ArrowList ar, ArrowChoice ar) | |
=> (a `ar` a) | The arrow to apply, |
-> (a `ar` b) | when this conditional holds. |
-> a `ar` a |
Apply a list arrow only when a conditional arrow produces any results.
When the conditional produces no results the output arrow behaves like the identity.
The second input arrow is used as the conditional, this allow
you to write: a `when` c
:: (ArrowList ar, ArrowChoice ar) | |
=> (a `ar` c) | When this condition holds, |
-> (a `ar` b) | then apply this arrow. |
-> a `ar` b |
Apply a list arrow only when a conditional arrow produces any results.
When the conditional produces no results the output arrow produces no results.
The first input arrow is used as the conditional, this allow you
to write: c `guards` a
filterA :: (ArrowChoice ar, ArrowList ar) => (a `ar` c) -> a `ar` aSource
Filter the results of an arrow with a predicate arrow, when the filter condition produces results the input is accepted otherwise it is excluded.
notA :: (ArrowList ar, ArrowChoice ar) => (a `ar` c) -> a `ar` aSource
Negation list arrow. Only accept the input when the condition produces no output.
orElse :: (ArrowList ar, ArrowChoice ar) => (a `ar` b) -> (a `ar` b) -> a `ar` bSource
Apply the input arrow, when the arrow does not produces any results the
second fallback arrow is applied.
Likely written infix like this a `orElse` b