Safe Haskell | Safe-Inferred |
---|---|
Language | Haskell98 |
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 arr => ArrowList arr where
- unlist :: ArrowList arr => [b] `arr` b
- unite :: ArrowList arr => (a `arr` (b, b)) -> a `arr` b
- none :: ArrowList arr => a `arr` b
- concatA :: ArrowPlus arr => [a `arr` b] -> a `arr` b
- list :: ArrowList arr => (a `arr` b) -> a `arr` [b]
- empty :: ArrowList arr => (a `arr` b) -> a `arr` Bool
- isA :: ArrowList arr => (a -> Bool) -> a `arr` a
- ifA :: (ArrowList arr, ArrowChoice arr) => (a `arr` c) -> (a `arr` b) -> (a `arr` b) -> a `arr` b
- when :: (ArrowList arr, ArrowChoice arr) => (a `arr` a) -> (a `arr` b) -> a `arr` a
- guards :: (ArrowList arr, ArrowChoice arr) => (a `arr` c) -> (a `arr` b) -> a `arr` b
- filterA :: (ArrowChoice arr, ArrowList arr) => (a `arr` c) -> a `arr` a
- notA :: (ArrowList arr, ArrowChoice arr) => (a `arr` c) -> a `arr` a
- orElse :: (ArrowList arr, ArrowChoice arr) => (a `arr` b) -> (a `arr` b) -> a `arr` b
- maybeL :: ArrowList arr => Maybe a `arr` a
- optional :: (ArrowChoice arr, ArrowList arr) => (a `arr` b) -> a `arr` Maybe b
ArrowList type class.
class Arrow arr => ArrowList arr where Source
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.
Monad m => ArrowList (ListTArrow m) |
Creating list arrows.
unite :: ArrowList arr => (a `arr` (b, b)) -> a `arr` b Source
Take the output of an arrow producing two results and concatenate them into the result of the list arrow.
concatA :: ArrowPlus arr => [a `arr` b] -> a `arr` b Source
Collect the results of applying multiple arrows to the same input.
Collecting the results.
list :: ArrowList arr => (a `arr` b) -> a `arr` [b] Source
Collect the entire results of an list arrow as a singleton value in the result list.
empty :: ArrowList arr => (a `arr` b) -> a `arr` Bool Source
Returns a Bool
indicating whether the input arrow produce any results.
Conditional and filter arrows.
:: (ArrowList arr, ArrowChoice arr) | |
=> (a `arr` c) | Arrow used as condition. |
-> (a `arr` b) | Arrow to use when condition has results. |
-> (a `arr` b) | Arrow to use when condition has no results. |
-> a `arr` 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 arr, ArrowChoice arr) | |
=> (a `arr` a) | The arrow to apply, |
-> (a `arr` b) | when this conditional holds. |
-> a `arr` 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 arr, ArrowChoice arr) | |
=> (a `arr` c) | When this condition holds, |
-> (a `arr` b) | then apply this arrow. |
-> a `arr` 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 arr, ArrowList arr) => (a `arr` c) -> a `arr` a Source
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 arr, ArrowChoice arr) => (a `arr` c) -> a `arr` a Source
Negation list arrow. Only accept the input when the condition produces no output.
orElse :: (ArrowList arr, ArrowChoice arr) => (a `arr` b) -> (a `arr` b) -> a `arr` b infix 8 Source
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