Control.Arrow.Machine.Misc.Discrete

Discrete type

This module should be imported manually. Qualified import is recommended.

This module provides an abstraction that continuous values with finite number of changing points.

>>> import qualified Control.Arrow.Machine.Misc.Discrete as D
>>> run (D.hold "apple" >>> D.arr reverse >>> D.edge) ["orange", "grape"]
["elppa", "egnaro", "eparg"]

In above example, input data of "reverse" is continuous. But the "D.edge" transducer extracts changing points without calling string comparison.

This is possible because the intermediate type T has the information of changes together with the value information.

data T a

The discrete signal type.

updates :: T a -> Event ()

value :: T a -> a

arr :: ArrowApply a => (b -> c) -> ProcessA a (T b) (T c)

arr2 :: ArrowApply a => (b1 -> b2 -> c) -> ProcessA a (T b1, T b2) (T c)

arr3 :: ArrowApply a => (b1 -> b2 -> b3 -> c) -> ProcessA a (T b1, T b2, T b3) (T c)

arr4 :: ArrowApply a => (b1 -> b2 -> b3 -> b4 -> c) -> ProcessA a (T b1, T b2, T b3, T b4) (T c)

arr5 :: ArrowApply a => (b1 -> b2 -> b3 -> b4 -> b5 -> c) -> ProcessA a (T b1, T b2, T b3, T b4, T b5) (T c)

constant :: ArrowApply a => c -> ProcessA a b (T c)

unsafeConstant :: ArrowApply a => c -> ProcessA a b (T c)

Constant without initial notifications. Users must manage initialization manually.

hold :: ArrowApply a => b -> ProcessA a (Event b) (T b)

accum :: ArrowApply a => b -> ProcessA a (Event (b -> b)) (T b)

fromEq :: (ArrowApply a, Eq b) => ProcessA a b (T b)

edge :: ArrowApply a => ProcessA a (T b) (Event b)

asUpdater :: ArrowApply a => a b c -> ProcessA a (T b) (Event c)

kSwitch :: ArrowApply a => ProcessA a b (T c) -> ProcessA a (b, T c) (Event t) -> (ProcessA a b (T c) -> t -> ProcessA a b (T c)) -> ProcessA a b (T c)

dkSwitch :: ArrowApply a => ProcessA a b (T c) -> ProcessA a (b, T c) (Event t) -> (ProcessA a b (T c) -> t -> ProcessA a b (T c)) -> ProcessA a b (T c)

Discrete algebra

Calculations between discrete types.

An example is below.

holdAdd ::
    (ArrowApply a, Num b) =>
    ProcessA a (Event b, Event b) (Discrete b)
holdAdd = proc (evx, evy) ->
  do
    x <- D.hold 0 -< evx
    y <- D.hold 0 -< evy
    D.eval (refer fst + refer snd) -< (x, y)

The last line is equivalent to "arr2 (+) -< (x, y)". Using Alg, you can construct more complex calculations between discrete signals.

newtype Alg a i o

Discrete algebra type.

Constructors

Alg

Fields

eval :: ProcessA a i (T o)

Instances

ArrowApply a => Functor (Alg a i)

ArrowApply a => Applicative (Alg a i)

(ArrowApply a, Num o) => Num (Alg a i o)

refer :: ArrowApply a => (e -> T b) -> Alg a e b