[Haskell-cafe] the Haskell "with" "pattern"?
jeremy at n-heptane.com
Wed Aug 6 03:25:41 EDT 2008
At Wed, 6 Aug 2008 00:43:55 -0500,
Galchin, Vasili wrote:
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> 1) Is there a common assumed semantics across all of the Haskell "with"
> things? withString? withData?
A vague semantic is that some resource is acquired, used, and then released.
> 2) If the answer to 1) is yes, then does this imply some kind of
> polymorphism? Couldn't "with" be "reduced" to a higher order function then
I think Control.Exception.bracket is used to implement many, but not
all, of the with* functions.
> newThing :: IO a
> newThing = ...
> destroyThing :: a -> IO b
> destroyThing ...
> withThing :: (Thing -> IO a) -> IO a
> withThing useThing = bracket newThing destroyThing useThing
I have not fully answered either of your questions, but hopefully this
is a start.
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