[Haskell-cafe] Explicitly passing an argument to an arrow
byorgey at seas.upenn.edu
Wed Oct 3 12:55:34 CEST 2012
On Wed, Oct 03, 2012 at 10:41:25AM +0200, Alfredo Di Napoli wrote:
> Hello everyone,
> sorry for the dumb question but I'm wrapping my head around arrow just from
> this morning.
> Consider this toy function to swap argument of a tuple:
> swapA' :: (Arrow a) => a ((b,c), (b,c)) (c,b)
> swapA' = swapFirst >>> swapSecond
> swapFirst = first $ arr snd
> swapSecond = second $ arr fst
> It works but requires to pass a tuple of tuple, namely ((b,c), (b,c)).
> How can I explicitly pass my tuple of tuple to swapFirst so I can simply
> swapA' (1,2)
> and get the correct result?
swapA' = dup >>> swapFirst >>> swapSecond
dup = id &&& id
I'm afraid I'm not confident I really understand your question,
however, so if that doesn't answer it, try asking again!
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