May 2003 - Haskell-Cafe

Why no findM ? simple Cat revisited
by Ahn Ki-yung 11 Nov '03

11 Nov '03

Simple Cat (revisitied) \begin{code} import IO findM f [] = return Nothing findM f (x:xs) = do { v <- x; if f v then return (Just v) else findM f xs } isLeft (Left _) = True isLeft _ = False main = findM (isLeft) (hCat stdin) where hCat h = try (hGetLine h) : hCat h \end{code} This is my answer for the question of my own, which is posted a couple There are mapM, filterM in the Haskell 98 Standard Library. But why no findM there ? As you can see from simple cat, it seems quite useful. I think fildM should be added to the module Monad. -- Ahn Ki-yung

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How to... use haskell 'functions' in C(++) sources ?
by Antoine Utonium 02 Jun '03

02 Jun '03

Everything is in the title. I like "simplicity" of Haskell and would like to use what i write in my c/c++ programs. Thanks a lot by advance.

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RE: Help: writing ffi bindings to a C library
by Bayley, Alistair 31 May '03

31 May '03

So... I'm still trying to write this Oracle OCI ffi binding. Can anyone tell me how to declare the Haskell type for this function: sword OCIEnvCreate (OCIEnv **envp, ub4 mode, dvoid *ctxp, dvoid *(*malocfp)(dvoid *ctxp, size_t size), dvoid *(*ralocfp)(dvoid *ctxp, dvoid *memptr, size_t newsize), void (*mfreefp)(dvoid *ctxp, dvoid *memptr), size_t xtramem_sz, dvoid **usrmempp); Note that when I use it, I'm passing 0 (NULL) into almost all of the args, so the usage in C is typically: rc = OCIEnvCreate(&envhp, OCI_DEFAULT, 0, 0, 0, 0, 0, 0); i.e. I don't care about most of the args, so that should make the Haskell declaration simpler. Some of the arguments are pointers to functions, for example. What I can't figure out is how to declare the type of the first arg. Is is Ptr (Ptr OCIEnv) ? Here's what I have so far (not much, I know): > module Main where > import Foreign > import Foreign.C.Types > import Foreign.C.String > import Foreign.Ptr > data OCIEnv > foreign import ccall "oci.h OCIEnvCreate" ociEnvCreate :: Ptr OCIEnv -> Int -> Int -> Int -> Int -> Int -> Int -> Int -> Int -----Original Message----- From: Ronald Legere [mailto:rjljr2@yahoo.com] Sent: 21 May 2003 20:32 To: 'haskell-cafe(a)haskell.org' Subject: Re: Help: writing ffi bindings to a C library Agreeing with David, but I like to use types rather than (). YOu can do this because, in ghc, you can write: data Blah with no rhs, and it is understood to be an 'opaque' type. Ghc beleives any claims you make about passing Ptr Blah back and forth to C in your foreign import declarations <* Grin *>. As for passing structures back and forth, and accessing the components, you can do it from Haskell or from the "c-side"... I can send you a sample of doing it from haskell if you wish. Ron --- David Roundy <droundy(a)abridgegame.org> wrote: > On Wed, May 21, 2003 at 04:27:10PM +0100, Bayley, > Alistair wrote: > > construct a Ptr a? What type should "a" be?). > > Unless you actually need to ever access their > contents, I'd just define the > pointers to be of type Ptr (), essentially like a > void * pointer in C. No > need to use Storable if they are only ever accessed > through C functions > (which I would hope would be the case). > -- ***************************************************************** The information in this email and in any attachments is confidential and intended solely for the attention and use of the named addressee(s). This information may be subject to legal professional or other privilege or may otherwise be protected by work product immunity or other legal rules. It must not be disclosed to any person without our authority. If you are not the intended recipient, or a person responsible for delivering it to the intended recipient, you are not authorised to and must not disclose, copy, distribute, or retain this message or any part of it. *****************************************************************

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RE: how to break up a large module?
by Simon Peyton-Jones 30 May '03

30 May '03

A non-exported function can be inlined, and its definition deleted. If there is only one call site, it can be inlined no matter how big it is. S | -----Original Message----- | From: haskell-cafe-admin(a)haskell.org [mailto:haskell-cafe-admin@haskell.org] On Behalf Of Jerzy | Karczmarczuk | Sent: 30 May 2003 14:04 | To: haskell-cafe(a)haskell.org | Subject: Re: how to break up a large module? | | Simon Marlow wrote: | | > Be careful about accidental overloading: | ... | | > Be careful with exports. Prune export lists to just those functions | > which need to be exported. | | | How a too long export list can slow-down the target program? | | Jerzy Karczmarczuk | | _______________________________________________ | Haskell-Cafe mailing list | Haskell-Cafe(a)haskell.org | http://www.haskell.org/mailman/listinfo/haskell-cafe

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by tony2003＠yahoo.ca 30 May '03

30 May '03

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RE: how to break up a large module?
by Simon Marlow 30 May '03

30 May '03

> I recently spent a couple of hours breaking up a large module > (2.5k lines) > into several smaller modules. When I finally got it working, > I found that > my program took about 60% longer to run. This was running ghc with -O > optimization. > > Any suggestions how to go about breaking up a module in such > a way that it > doesn't slow things down? Do I just have to go adding INLINE > directives to > all my functions? Or is there some other trick I could use? Be careful about accidental overloading: GHC will specialise if it can see the uses of a function within a single module, but not when the function is in another module. Put type signatures on everything, and consider using SPECIALISE pragmas to eliminate overloading. Be careful with exports. Prune export lists to just those functions which need to be exported. Cheers, Simon

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RE: how to break up a large module?
by Simon Peyton-Jones 30 May '03

30 May '03

60% longer is a lot. I'm surprised. I'd try compiling the whole thing both ways with profiling on and see if that reveals anything S | -----Original Message----- | From: haskell-cafe-admin(a)haskell.org [mailto:haskell-cafe-admin@haskell.org] On Behalf Of David | Roundy | Sent: 30 May 2003 13:06 | To: haskell-cafe(a)haskell.org | Subject: how to break up a large module? | | I recently spent a couple of hours breaking up a large module (2.5k lines) | into several smaller modules. When I finally got it working, I found that | my program took about 60% longer to run. This was running ghc with -O | optimization. | | Any suggestions how to go about breaking up a module in such a way that it | doesn't slow things down? Do I just have to go adding INLINE directives to | all my functions? Or is there some other trick I could use? | | For the moment I've reverted to my single big file method, but it certainly | would be handy to be able to break that up so that it wouldn't take so long | to recompile. | -- | David Roundy | http://www.abridgegame.org | _______________________________________________ | Haskell-Cafe mailing list | Haskell-Cafe(a)haskell.org | http://www.haskell.org/mailman/listinfo/haskell-cafe

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how to break up a large module?
by David Roundy 30 May '03

30 May '03

I recently spent a couple of hours breaking up a large module (2.5k lines) into several smaller modules. When I finally got it working, I found that my program took about 60% longer to run. This was running ghc with -O optimization. Any suggestions how to go about breaking up a module in such a way that it doesn't slow things down? Do I just have to go adding INLINE directives to all my functions? Or is there some other trick I could use? For the moment I've reverted to my single big file method, but it certainly would be handy to be able to break that up so that it wouldn't take so long to recompile. -- David Roundy http://www.abridgegame.org

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Immediate business proposal
by DR MICHAEL KAGIDA 30 May '03

30 May '03

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Hello haskell-cafe !
by DR MICHAEL KAGIDA 29 May '03

29 May '03

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