[Haskell-cafe] Arrows extentions and ArrowApplicable

[Ross Paterson]

On Fri, Aug 28, 2009 at 02:33:08PM +0200, Maciej Piechotka wrote:
> 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

You can write

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

(See the Arrow notation section of the GHC User's Guide.)