[Haskell-cafe] Arrows extentions and ArrowApplicable

[Maciej Piechotka]

Arrows syntax supports Arrow, ArrowChoice(if, case etc.) and
ArrowLoop(rec) - but not ArrowApplicable. Therefore it is not possible
to write:

proc x -> do
	a <- someArrow -< x
	a -< x

but

proc x -> do
	a <- someArrow -< x
	app -< (a, x)


and

proc x -> do
	a <- someArrow -< x
	app -< (otherArrow a, x)

instead of

proc x -> do
	a <- someArrow -< x
	otherArrow a -< x

Such approach adds some syntax sugar but without adding any additional
keyword and IMHO it can simplify writing ArrowApply (especially Kleisli
IO).

Regards
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