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Today's Topics:
1. bracket or how to release ressources. (PICCA Frederic-Emmanuel)
2. Re: bracket or how to release ressources. (Rein Henrichs)
3. Re: bracket or how to release ressources.
(PICCA Frederic-Emmanuel)
----------------------------------------------------------------------
Message: 1
Date: Sat, 26 Mar 2016 18:59:38 +0000
From: PICCA Frederic-Emmanuel
<[email protected]>
To: "[email protected]" <[email protected]>
Subject: [Haskell-beginners] bracket or how to release ressources.
Message-ID:
<a2a20ec3b8560d408356cac2fc148e53b305e...@sun-dag3.synchrotron-soleil.fr>
Content-Type: text/plain; charset="us-ascii"
Hello, I try to write a sort of withxxx method whcih release a file
withH5File :: FilePath -> (HId_t -> IO r) -> IO r
withH5File name = bracket (withCString name acquire) h5f_close
where
acquire file = h5f_open file h5f_ACC_RDONLY h5p_DEFAULT
In my case h5f_open return a HId_t value (HId_t Int)
If something went wrong the returned value is negativ.
In that case I do not need to h5f_close the file but instead return an error
My question is how should I write the bracket part when the finaliser
(h5f_close) depends on the result of the acquire part.
thanks for your help
Frederic
------------------------------
Message: 2
Date: Sat, 26 Mar 2016 19:40:18 +0000
From: Rein Henrichs <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] bracket or how to release ressources.
Message-ID:
<cajp6g8z6gf+rbzowkepz-9pveqhuu-a7g1vucyk0zyefure...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
If your finalization step depends on the result of your action, bracket is
not an appropriate choice. It is for resources that are known at the time
they are acquired.
On Sat, Mar 26, 2016 at 11:59 AM PICCA Frederic-Emmanuel <
[email protected]> wrote:
> Hello, I try to write a sort of withxxx method whcih release a file
>
> withH5File :: FilePath -> (HId_t -> IO r) -> IO r
> withH5File name = bracket (withCString name acquire) h5f_close
> where
> acquire file = h5f_open file h5f_ACC_RDONLY h5p_DEFAULT
>
> In my case h5f_open return a HId_t value (HId_t Int)
> If something went wrong the returned value is negativ.
> In that case I do not need to h5f_close the file but instead return an
> error
>
> My question is how should I write the bracket part when the finaliser
> (h5f_close) depends on the result of the acquire part.
>
> thanks for your help
>
> Frederic
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>
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Message: 3
Date: Sun, 27 Mar 2016 07:33:27 +0000
From: PICCA Frederic-Emmanuel
<[email protected]>
To: "The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell" <[email protected]>
Subject: Re: [Haskell-beginners] bracket or how to release ressources.
Message-ID:
<a2a20ec3b8560d408356cac2fc148e53b305e...@sun-dag3.synchrotron-soleil.fr>
Content-Type: text/plain; charset="us-ascii"
Looking at the haskellforall I found something which should be interesting in
my case
A type dedicated to this sort of problem. the Resource Monad.
I will investigate :)
thanks
Frederic
[1] http://www.haskellforall.com/2013/06/the-resource-applicative.html
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