DeepArrow-0.0.1: Arrows for "deep application"Source codeContentsIndex
Control.Arrow.DeepArrow
Portabilityportable
Stabilityexperimental
Maintainerconal@conal.net
Contents
The DeepArrow class
Composable function extractors
Composable input extractors
Misc functions
Some utilities
Description
"Deep arrows" as an Arrow subclass.
Synopsis
class Arrow ~> => DeepArrow (~>) where
result :: (b ~> b') -> (a -> b) ~> (a -> b')
idA :: a ~> a
dupA :: a ~> (a, a)
fstA :: (a, b) ~> a
sndA :: (a, b) ~> b
funF :: (c -> a, b) ~> (c -> (a, b))
funS :: (a, c -> b) ~> (c -> (a, b))
funR :: (a -> c -> b) ~> (c -> a -> b)
curryA :: ((a, b) -> c) ~> (a -> b -> c)
uncurryA :: (a -> b -> c) ~> ((a, b) -> c)
swapA :: (a, b) ~> (b, a)
lAssocA :: (a, (b, c)) ~> ((a, b), c)
rAssocA :: ((a, b), c) ~> (a, (b, c))
funFirst :: DeepArrow ~> => (d ~> (c -> a)) -> (d, b) ~> (c -> (a, b))
funSecond :: DeepArrow ~> => (d ~> (c -> b)) -> (a, d) ~> (c -> (a, b))
funResult :: DeepArrow ~> => (d ~> (c -> b)) -> (a -> d) ~> (c -> a -> b)
inpF :: DeepArrow ~> => ((a, b) -> c) ~> (a -> b -> c)
inpS :: DeepArrow ~> => ((a, b) -> c) ~> (b -> a -> c)
inpFirst :: DeepArrow ~> => ((a -> c) ~> (d -> a' -> c)) -> ((a, b) -> c) ~> (d -> (a', b) -> c)
inpSecond :: DeepArrow ~> => ((b -> c) ~> (d -> b' -> c)) -> ((a, b) -> c) ~> (d -> (a, b') -> c)
flipA :: DeepArrow ~> => (a -> c -> b) ~> (c -> a -> b)
unzipA :: DeepArrow ~> => (a ~> (b, c)) -> (a ~> b, a ~> c)
(->|) :: (DeepArrow ~>, FunArr ~> w) => w (a -> b) -> w (b -> c) -> w (a -> c)
The DeepArrow class
class Arrow ~> => DeepArrow (~>) whereSource

Arrows for deep application. Most of these methods could be defined using arr, but arr is not definable for some types. If your DeepArrow instance has arr, you might want to use these implementations

    idA      = arr id
    fstA     = arr fst
    dupA     = arr (\ x -> (x,x))
    sndA     = arr snd
    funF     = arr (\ (f,b) -> \ c -> (f c, b))
    funS     = arr (\ (a,f) -> \ c -> (a, f c))
    funR     = arr flip
    curryA   = arr curry
    uncurryA = arr uncurry
    swapA    = arr (\ (a,b) -> (b,a))
    lAssocA  = arr (\ (a,(b,c)) -> ((a,b),c))
    rAssocA  = arr (\ ((a,b),c) -> (a,(b,c)))

If your DeepArrow instance does not have arr, you'll have to come up with other definitions. In any case, I recommend the following definitions, which mirror Arrow defaults while avoiding arr. Be sure also to define arr or pure to yield an error message (rather than ping-ponging infinitely between them via the Arrow default definitions).

    second f = swapA >>> first f >>> swapA
    f &&& g  = dupA  >>> f *** g

In a few cases, there are default methods, as noted below. The defaults do not use arr.

Methods
result :: (b ~> b') -> (a -> b) ~> (a -> b')Source
Direct arrow into a function's result. Analogous to first and second.
idA :: a ~> aSource
Identity.
dupA :: a ~> (a, a)Source
Duplicate.
fstA :: (a, b) ~> aSource
Extract first.
sndA :: (a, b) ~> bSource
Extract second.
funF :: (c -> a, b) ~> (c -> (a, b))Source
Extract function from first element.
funS :: (a, c -> b) ~> (c -> (a, b))Source
Extract function from second element.
funR :: (a -> c -> b) ~> (c -> a -> b)Source
Extract function from result.
curryA :: ((a, b) -> c) ~> (a -> b -> c)Source
Curry arrow.
uncurryA :: (a -> b -> c) ~> ((a, b) -> c)Source
Uncurry arrow.
swapA :: (a, b) ~> (b, a)Source
Swap elements. Has default.
lAssocA :: (a, (b, c)) ~> ((a, b), c)Source
Left-associate. Has default.
rAssocA :: ((a, b), c) ~> (a, (b, c))Source
Right-associate. Has default.
show/hide Instances
DeepArrow (->)
(DeepArrow ar, DeepArrow ar') => DeepArrow (Pair2 ar ar')
Composable function extractors
funFirst :: DeepArrow ~> => (d ~> (c -> a)) -> (d, b) ~> (c -> (a, b))Source
Promote a function extractor into one that reaches into the first element of a pair.
funSecond :: DeepArrow ~> => (d ~> (c -> b)) -> (a, d) ~> (c -> (a, b))Source
Promote a function extractor into one that reaches into the second element of a pair.
funResult :: DeepArrow ~> => (d ~> (c -> b)) -> (a -> d) ~> (c -> a -> b)Source
Promote a function extractor into one that reaches into the result element of a function.
Composable input extractors
inpF :: DeepArrow ~> => ((a, b) -> c) ~> (a -> b -> c)Source
Extract the first component of a pair input.
inpS :: DeepArrow ~> => ((a, b) -> c) ~> (b -> a -> c)Source
Extract the second component of a pair input.
inpFirst :: DeepArrow ~> => ((a -> c) ~> (d -> a' -> c)) -> ((a, b) -> c) ~> (d -> (a', b) -> c)Source
inpSecond :: DeepArrow ~> => ((b -> c) ~> (d -> b' -> c)) -> ((a, b) -> c) ~> (d -> (a, b') -> c)Source
Misc functions
flipA :: DeepArrow ~> => (a -> c -> b) ~> (c -> a -> b)Source
Flip argument order
unzipA :: DeepArrow ~> => (a ~> (b, c)) -> (a ~> b, a ~> c)Source
Like unzip but for DeepArrow arrows instead of lists.
Some utilities
(->|) :: (DeepArrow ~>, FunArr ~> w) => w (a -> b) -> w (b -> c) -> w (a -> c)Source
Compose wrapped functions
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