Hey,
I just wondered if you can define Applicative instances for arrows?
Basicly what I thought of is:
I have a type for my arrow which is "CollectA" (using HXT here):
type CollectA a = SomeArrow XmlTree a
And my datatype which I want to construct:
data Test = Test
{ testString :: String
, testInt :: Int
}
With the functions:
collectString :: CollectA String
collectInt :: CollectA Int
Now, what I currently do is something like:
collectTest :: CollectA Test
collectTest = getChildren
>>> someOtherArrow -- etc...
>>> proc foo -> do
s <- collectString -< foo
i <- collectInt -< foo
returnA -< Test s i
With Applicatives that proc-do-part would become:
collectTest' :: CollectA Test
collectTest' = ... -- arrow stuff
>>> Test <$> collectString
<*> collectInt
Is something like this possible? I don't understand that "proc" part
good enough to see what it's actually doing there, maybe someone with a
better understanding for this could help out? :)
Thx,
- Nils
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