April 2004 - Glasgow-haskell-users

RE: Haskell performance
by Simon Marlow 07 Apr '04

07 Apr '04

> Okay. What's really bothering me is that I can't find any good > indication of what to do to get IO faster. Do I need to FFI the whole > thing and have a C library give me large chunks? Or can I get by with > hGet/PutArray? If so, what sizes should they be? Should I use memory > mapped files? hGet/PutArray should be pretty quick. For small requests, they get the usual buffering treatment that other Handle operations have, and for large requests the buffer is bypassed. For reading a file in one go, hGetArray (or hGetBuf) is the way to go. GHC itself uses hGetBuf for reading source files, hGetArray for reading interface files, and hPutBuf for writing output. Memory mapped files (mmap) should be even quicker. But then you'll have to use peek & co from Foreign to access the bytes. Cheers, Simon

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RE: turn off let floating
by Simon Peyton-Jones 07 Apr '04

07 Apr '04

Strangely (and bogusly) there is no such flag in GHC6.2. Someone must have noticed this already because it's there in the HEAD (-fno-full-laziness), and has been since Feb 2004. Strange. Simon | -----Original Message----- | From: glasgow-haskell-users-bounces(a)haskell.org [mailto:glasgow-haskell-users- | bounces(a)haskell.org] On Behalf Of Bernard James POPE | Sent: 06 April 2004 09:24 | To: glasgow-haskell-users(a)haskell.org | Cc: Bernard James POPE | Subject: turn off let floating | | Hi all, | | In the documentation for System.IO.Unsafe | it says: | | Make sure that the either you switch off let-floating, | or that the call to unsafePerformIO cannot float outside a lambda. | | My question is how can you turn off let floating? I can't seem to | find a flag that suggests this behaviour. | | Cheers, | Bernie. | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users(a)haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

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RE: :kind feature request in ghci
by Simon Peyton-Jones 05 Apr '04

05 Apr '04

Done! In the HEAD anyway, and will therefore be in 6.4 Simon Prelude> :k Int Int :: * Prelude> :k Maybe Maybe :: * -> * Prelude> :k Maybe Int Maybe Int :: * Prelude> :q | -----Original Message----- | From: glasgow-haskell-users-bounces(a)haskell.org [mailto:glasgow-haskell-users- | bounces(a)haskell.org] On Behalf Of S. Alexander Jacobson | Sent: 27 March 2004 15:33 | To: GHC users | Subject: :kind feature request in ghci | | I keep running into kind errors (see my most | recent post on Haskell cafe). Would it be | possible for ghci to expose a :kind function | that operates on types the way :type operates on | values? | | Alternatively, is there another way to | figure out how to create an instance of | a class like this? | | class MyClass a b where emptyVal::a b | | Here are one of the thing that don't work: | | type MyType a = [a] | instance MyClass (MyType a) a where emptyVal=[] | | And I have no idea why... | | -Alex- | | _________________________________________________________________ | S. Alexander Jacobson mailto:me@alexjacobson.com | tel:917-770-6565 http://alexjacobson.com | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users(a)haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

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RE: Subject: Generic compilation warnings...
by Simon Peyton-Jones 05 Apr '04

05 Apr '04

It should be ignored, but I've fixed it anyway. Thanks for mentioning it. Simon | -----Original Message----- | From: glasgow-haskell-users-bounces(a)haskell.org [mailto:glasgow-haskell-users- | bounces(a)haskell.org] On Behalf Of MR K P SCHUPKE | Sent: 17 February 2004 15:07 | To: glasgow-haskell-users(a)haskell.org | Subject: Subject: Generic compilation warnings... | | When deriving Data with all warnings enabled, for example compiling the | following line: | | data TestType = TestType Int deriving (Typeable,Data) | | ghc 6.2 gives the following warnings: | | Warning: Pattern match(es) are non-exhaustive | In a case alternative: | Patterns not matched: GHC.Base.I# #x with #x `notElem` [1#] | | Is there a problem with the 'derived' code, or should this warning be | ignored? | | regards, | Keean Schupke. | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users(a)haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

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RE: [Haskell] Dynamically loading wxhaskell?
by Simon Marlow 03 Apr '04

03 Apr '04

> On Thu, Apr 01, 2004 at 10:00:23AM +0100, Simon Marlow wrote: > > > > > Has anyone succeeded in getting wxhaskell to work under > ghci on Linux? > > > On my system, I get an error message > > > > > > Loading package unix ... ghc-6.2: can't load .so/.DLL for: dl > > > (libdl.so: cannot open shared object file: No such file > or directory) > > > > > > This sounds like it has nothing to do with wxhaskell, but is a GHC > > > problem. Any pointers? > > > > Is libdl.so in the usual place? (/usr/lib on my system) > > Yes. > > (FYI, this is a Debian unstable system.) > > Everything works with GHC, by the way. Very strange. Is /usr/lib/libdl.so perhaps a symlink to a library that doesn't exist? That could happen if an upgrade had gone wrong, perhaps. Cheers, Simon

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