Re: framework for composing monads?

2001-02-18 Thread Elke Kasimir 

(Moving to haskell cafe...)

On 18-Feb-2001 Manuel M. T. Chakravarty wrote:
 It is even acceptable for me to manage the state in C -
 independent of the API design - but then some time there 
 will be the question: Why do I always say that that Haskell 
 is the better programming language, when I'm
 really doing all the tricky stuff in C?...
 
 Sure - therefore, I proposed to use `IORef's rather than C
 routines. 

Thanks for the hint! 

I took a look at them and now have some questions:

a) It is clear that I need some C-link to access the cli/odbc lib.
Up to now I planned to use Haskell Direct for this. Except of this, I want
to stick to Haskell 98 and seek for maximal portability. 

Practically, this raises the question of wether nhc and hbc support hslibs
or else I can provide a substitute for IORef's for these compilers.

Can someone give me hint?

b) What I finally need is "hidden state". My first attempt to get one 
using IORefs is:

 import IOExts

 state :: IORef Int
 state = unsafePerformIO $ newIORef 0

 main = seq state $ do
   writeIORef state 1
   currstate - readIORef state
   putStr (show currstate)

Is this the right way?

Cheers,
Elke


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Re: framework for composing monads?

2001-02-18 Thread Manuel M. T. Chakravarty 

Elke Kasimir [EMAIL PROTECTED] wrote,

 (Moving to haskell cafe...)
 
 On 18-Feb-2001 Manuel M. T. Chakravarty wrote:
  It is even acceptable for me to manage the state in C -
  independent of the API design - but then some time there 
  will be the question: Why do I always say that that Haskell 
  is the better programming language, when I'm
  really doing all the tricky stuff in C?...
  
  Sure - therefore, I proposed to use `IORef's rather than C
  routines. 
 
 Thanks for the hint! 
 
 I took a look at them and now have some questions:
 
 a) It is clear that I need some C-link to access the cli/odbc lib.
 Up to now I planned to use Haskell Direct for this. Except of this, I want
 to stick to Haskell 98 and seek for maximal portability. 

I am all for portable code, too.

 Practically, this raises the question of wether nhc and hbc support hslibs
 or else I can provide a substitute for IORef's for these compilers.

nhc does supports `IORef's (they come in the module
IOExtras).  I am not sure whether H/Direct works with nhc,
though.  Sigbjorn should be able to answer this.

 b) What I finally need is "hidden state". My first attempt to get one 
 using IORefs is:
 
  import IOExts
 
  state :: IORef Int
  state = unsafePerformIO $ newIORef 0
 
  main = seq state $ do
writeIORef state 1
currstate - readIORef state
putStr (show currstate)
 
 Is this the right way?

Yes, except that you want to have

  {-# NOINLINE state #-}

too.  Wouldn't be nice if ghc were to choose to inline
`state', would it? ;-)

Cheers,
Manuel

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Re: framework for composing monads?

2001-02-15 Thread Jan Kort 


Andy Gill's Monad Template Library is good for that, but the link
from the Haskell library page is broken:

  http://www.cse.ogi.edu/~andy/monads/doc.htm

  Jan

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