[Haskell-cafe] Arrows extentions and ArrowApplicable

2009-08-28 Thread 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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Re: [Haskell-cafe] Arrows extentions and ArrowApplicable

2009-08-28 Thread 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.)
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