[Haskell-cafe] Question on a common pattern

Chris Dornan chris at chrisdornan.com
Mon Mar 14 17:12:06 CET 2011

Your first line is entirely natural.


The alternative doesn't look right at all.


I am not aware of a more concise alternative to this general construction
(assuming there are multiple case alternative, and that the work can't be
done with library functions).




From: haskell-cafe-bounces at haskell.org
[mailto:haskell-cafe-bounces at haskell.org] On Behalf Of tsuraan
Sent: 14 March 2011 15:49
To: haskell-cafe at haskell.org
Subject: [Haskell-cafe] Question on a common pattern


In my code, I'm doing this quite a lot:

x <- someIO
case x of
  Opt1 -> ...

Having a line for extracting the value from the IO (or STM) and then
acting on the value seems unnatural.  Is there a more concise way to
do this?  This code:

case someIO of
  Opt1 -> ...

Doesn't work, but is there something like that, that is valid?

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