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Today's Topics:
1. Re: monads / do syntax (Thiago Negri)
2. Re: Error Loading Stdm.lhs in Haskell platform 2012
(Stephen Tetley)
3. Thread Blocking (mukesh tiwari)
4. Re: Thread Blocking (Eugene Perederey)
5. Re: Thread Blocking (mukesh tiwari)
6. Re: Thread Blocking (Eugene Perederey)
----------------------------------------------------------------------
Message: 1
Date: Tue, 4 Sep 2012 13:38:42 -0300
From: Thiago Negri <[email protected]>
Subject: Re: [Haskell-beginners] monads / do syntax
To: Christopher Howard <[email protected]>
Cc: Haskell Beginners <[email protected]>
Message-ID:
<CABLneZvsjXsVTinNrhJG9hUkW_01d3-O=jeuqpjashs-ccp...@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
Go line by line, except the last one:
a) When you see the pattern "a <- b", just swap it with "b >>= \s ->";
b) When you see the pattern "b", put a ">>" at the end of the line.
In your case:
| h = (return 1 :: IO Integer) >>= \a ->
| return 2 >>= \b ->
| return (a + b + 1)
An example when you have a line without an assignment ("<-"), this:
| h = do a <- (return 1 :: IO Integer)
| b <- (return 2)
| putStrLn "Hello, world!"
| return (a + b + 1)
Turns into:
| h = (return 1 :: IO Integer) >>= \a ->
| return 2 >>= \b ->
| putStrLn "Hello, world!" >>
| return (a + b + 1)
2012/9/4 Christopher Howard <[email protected]>:
> What does the following do expression translate into? (I.e., using >>=
> operator and lambda functions.)
>
> code:
> --------
> h = do a <- (return 1 :: IO Integer)
> b <- (return 2)
> return (a + b + 1)
> --------
------------------------------
Message: 2
Date: Tue, 4 Sep 2012 17:40:45 +0100
From: Stephen Tetley <[email protected]>
Subject: Re: [Haskell-beginners] Error Loading Stdm.lhs in Haskell
platform 2012
To: Iwan Awaludin <[email protected]>
Cc: [email protected]
Message-ID:
<CAB2TPRDoOVD_M4Br-=vfgdggakw0p3xukh1qtyrtt4h2pmc...@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
The code for the book is written in Haskell '98, but recent versions
of GHC default to Haskell2010.
A salient difference between H98 and H2012 is the removed of n + k
patterns which generates the error you are seeing.
I can't find the exact command to use in the GHC docs to enable H98,
but you could try the following old flag which disables GHCs
extensions:
> ghci -fno-glasgow-exts
------------------------------
Message: 3
Date: Wed, 5 Sep 2012 00:24:30 +0530
From: mukesh tiwari <[email protected]>
Subject: [Haskell-beginners] Thread Blocking
To: [email protected]
Message-ID:
<CAFHZvE9pKn7_EM9t=x3sfay3oqvnmrmk_7xe9ro9jswbqpn...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Hello All
I was going trough Real World Haskell and it says "If we try to put a value
into an MVar that is already full, our thread is put to sleep until another
thread takes the value out". I wrote a simple code to block main
import Data.List
import Control.Concurrent
fun m = do
putMVar m 10
return ()
main = do
m <- newEmptyMVar
forkIO $ fun m
putMVar m 10
return ()
What I am expecting that main should be blocked at least couple of times
but its behaving more deterministically.
[mukesh.tiwari@ Programming]$ ghc-7.4.1 -threaded -fforce-recomp
Concurrent.hs
[1 of 1] Compiling Main ( Concurrent.hs, Concurrent.o )
Linking Concurrent ...
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
[mukesh.tiwari@ Programming]$
I am expecting to get thread blocked indefinitely on MVar at least half the
time. Could some one please tell me why this deterministic behavior ?
Regards
Mukesh Tiwari
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------------------------------
Message: 4
Date: Tue, 4 Sep 2012 12:02:51 -0700
From: Eugene Perederey <[email protected]>
Subject: Re: [Haskell-beginners] Thread Blocking
To: mukesh tiwari <[email protected]>
Cc: [email protected]
Message-ID:
<CAFTqo17X50xRZntCuG=7Z7LpEm=t8-xxlgfugbn+gmidrxv...@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
Why do you think main should block more than once?
I see only two possible scenarios: the fun thread puts to mvar first
thus blocking main,
or 10 is put into mvar in main, blocking the other thread indefinitely.
On 4 September 2012 11:54, mukesh tiwari <[email protected]> wrote:
> Hello All
> I was going trough Real World Haskell and it says "If we try to put a value
> into an MVar that is already full, our thread is put to sleep until another
> thread takes the value out". I wrote a simple code to block main
>
> import Data.List
> import Control.Concurrent
>
> fun m = do
> putMVar m 10
> return ()
>
>
> main = do
> m <- newEmptyMVar
> forkIO $ fun m
> putMVar m 10
> return ()
>
> What I am expecting that main should be blocked at least couple of times
> but its behaving more deterministically.
> [mukesh.tiwari@ Programming]$ ghc-7.4.1 -threaded -fforce-recomp
> Concurrent.hs
> [1 of 1] Compiling Main ( Concurrent.hs, Concurrent.o )
> Linking Concurrent ...
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> [mukesh.tiwari@ Programming]$
>
> I am expecting to get thread blocked indefinitely on MVar at least half the
> time. Could some one please tell me why this deterministic behavior ?
> Regards
> Mukesh Tiwari
>
>
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/beginners
>
--
Best,
Eugene Perederey
------------------------------
Message: 5
Date: Wed, 5 Sep 2012 00:46:36 +0530
From: mukesh tiwari <[email protected]>
Subject: Re: [Haskell-beginners] Thread Blocking
To: Eugene Perederey <[email protected]>
Cc: [email protected]
Message-ID:
<CAFHZvE-=bJVtdE9aRryYkkVg7V6u-GVj1G71h5q-o=cohvw...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Hi Eugene
Thank you for reply.
On Wed, Sep 5, 2012 at 12:32 AM, Eugene Perederey <
[email protected]> wrote:
> Why do you think main should block more than once?
> I see only two possible scenarios: the fun thread puts to mvar first
> thus blocking main,
>
So at least in this case I should get thread blocked indefinitely in an
MVar operation
> or 10 is put into mvar in main, blocking the other thread indefinitely.
>
or main will execute and fun thread will die. There are 50 - 50 chance for
this ( assuming both are equally likely ). I did some modification in my
code and Now I am consistently getting "Concurrent: thread blocked
indefinitely in an MVar operation"
import Data.List
import Control.Concurrent
fun m = do
putMVar m 10
return ()
main = do
m <- newEmptyMVar
forkIO $ fun m
putStrLn "I am inside main"
putMVar m 10
return ()
[mukesh.tiwari@ Programming]$ ghc-7.4.1 -threaded -fforce-recomp
Concurrent.hs
[1 of 1] Compiling Main ( Concurrent.hs, Concurrent.o )
Linking Concurrent ...
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
I am inside main
Concurrent: thread blocked indefinitely in an MVar operation
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
I am inside main
Concurrent: thread blocked indefinitely in an MVar operation
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
I am inside main
Concurrent: thread blocked indefinitely in an MVar operation
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
I am inside main
Concurrent: thread blocked indefinitely in an MVar operation
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
I am inside main
Concurrent: thread blocked indefinitely in an MVar operation
My question is why the outcome in first case is deterministic. Every time
the code executing ( at least half the time main thread should be blocked
) .
Regards
Mukesh Tiwari
>
> On 4 September 2012 11:54, mukesh tiwari <[email protected]>
> wrote:
> > Hello All
> > I was going trough Real World Haskell and it says "If we try to put a
> value
> > into an MVar that is already full, our thread is put to sleep until
> another
> > thread takes the value out". I wrote a simple code to block main
> >
> > import Data.List
> > import Control.Concurrent
> >
> > fun m = do
> > putMVar m 10
> > return ()
> >
> >
> > main = do
> > m <- newEmptyMVar
> > forkIO $ fun m
> > putMVar m 10
> > return ()
> >
> > What I am expecting that main should be blocked at least couple of times
> > but its behaving more deterministically.
> > [mukesh.tiwari@ Programming]$ ghc-7.4.1 -threaded -fforce-recomp
> > Concurrent.hs
> > [1 of 1] Compiling Main ( Concurrent.hs, Concurrent.o )
> > Linking Concurrent ...
> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> > [mukesh.tiwari@ Programming]$
> >
> > I am expecting to get thread blocked indefinitely on MVar at least half
> the
> > time. Could some one please tell me why this deterministic behavior ?
> > Regards
> > Mukesh Tiwari
> >
> >
> > _______________________________________________
> > Beginners mailing list
> > [email protected]
> > http://www.haskell.org/mailman/listinfo/beginners
> >
>
>
>
> --
> Best,
> Eugene Perederey
>
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------------------------------
Message: 6
Date: Tue, 4 Sep 2012 12:27:29 -0700
From: Eugene Perederey <[email protected]>
Subject: Re: [Haskell-beginners] Thread Blocking
To: mukesh tiwari <[email protected]>
Cc: [email protected]
Message-ID:
<caftqo16tp92gs9pnkadptsscj9qerb1xnhkh4_ctgowtybu...@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
I added a few prints to your code
fun m = do
putStrLn "fun1"
putMVar m 10
putStrLn "fun2"
main = do
m <- newEmptyMVar
forkIO $ fun m
putStrLn "main1"
putMVar m 10
putStrLn "main2"
It works 50/50 for me in Mac OS X 10.6.8.
On 4 September 2012 12:16, mukesh tiwari <[email protected]> wrote:
> Hi Eugene
> Thank you for reply.
>
> On Wed, Sep 5, 2012 at 12:32 AM, Eugene Perederey
> <[email protected]> wrote:
>>
>> Why do you think main should block more than once?
>> I see only two possible scenarios: the fun thread puts to mvar first
>> thus blocking main,
>
>
> So at least in this case I should get thread blocked indefinitely in an MVar
> operation
>
>>
>> or 10 is put into mvar in main, blocking the other thread indefinitely.
>
>
> or main will execute and fun thread will die. There are 50 - 50 chance for
> this ( assuming both are equally likely ). I did some modification in my
> code and Now I am consistently getting "Concurrent: thread blocked
> indefinitely in an MVar operation"
>
>
> import Data.List
> import Control.Concurrent
>
> fun m = do
> putMVar m 10
> return ()
>
>
> main = do
> m <- newEmptyMVar
> forkIO $ fun m
> putStrLn "I am inside main"
>
> putMVar m 10
> return ()
>
> [mukesh.tiwari@ Programming]$ ghc-7.4.1 -threaded -fforce-recomp
> Concurrent.hs
> [1 of 1] Compiling Main ( Concurrent.hs, Concurrent.o )
> Linking Concurrent ...
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> I am inside main
> Concurrent: thread blocked indefinitely in an MVar operation
>
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> I am inside main
> Concurrent: thread blocked indefinitely in an MVar operation
>
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> I am inside main
> Concurrent: thread blocked indefinitely in an MVar operation
>
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> I am inside main
> Concurrent: thread blocked indefinitely in an MVar operation
>
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
> I am inside main
> Concurrent: thread blocked indefinitely in an MVar operation
>
> My question is why the outcome in first case is deterministic. Every time
> the code executing ( at least half the time main thread should be blocked )
> .
>
> Regards
> Mukesh Tiwari
>
>>
>>
>> On 4 September 2012 11:54, mukesh tiwari <[email protected]>
>> wrote:
>> > Hello All
>> > I was going trough Real World Haskell and it says "If we try to put a
>> > value
>> > into an MVar that is already full, our thread is put to sleep until
>> > another
>> > thread takes the value out". I wrote a simple code to block main
>> >
>> > import Data.List
>> > import Control.Concurrent
>> >
>> > fun m = do
>> > putMVar m 10
>> > return ()
>> >
>> >
>> > main = do
>> > m <- newEmptyMVar
>> > forkIO $ fun m
>> > putMVar m 10
>> > return ()
>> >
>> > What I am expecting that main should be blocked at least couple of times
>> > but its behaving more deterministically.
>> > [mukesh.tiwari@ Programming]$ ghc-7.4.1 -threaded -fforce-recomp
>> > Concurrent.hs
>> > [1 of 1] Compiling Main ( Concurrent.hs, Concurrent.o )
>> > Linking Concurrent ...
>> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
>> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
>> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
>> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
>> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
>> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
>> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
>> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
>> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
>> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
>> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
>> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
>> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
>> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
>> > [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2
>> > [mukesh.tiwari@ Programming]$
>> >
>> > I am expecting to get thread blocked indefinitely on MVar at least half
>> > the
>> > time. Could some one please tell me why this deterministic behavior ?
>> > Regards
>> > Mukesh Tiwari
>> >
>> >
>> > _______________________________________________
>> > Beginners mailing list
>> > [email protected]
>> > http://www.haskell.org/mailman/listinfo/beginners
>> >
>>
>>
>>
>> --
>> Best,
>> Eugene Perederey
>
>
--
Best,
Eugene Perederey
------------------------------
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