ANNOUNCE: nhc98-1.16
nhc98-1.16 -- http://www.haskell.org/nhc98 We announce a new release, 1.16, of the Haskell compiler nhc98, with the following new features and bugfixes of note. * nhc98 once again builds on Windows (Cygwin) with ghc. * nhc98 now works correctly in the presence of gcc-3.x. * A large subset of the 'base' package of hierarchical libraries is now included in the build. * The primitive FFI mechanism has been updated to match the latest official spec, and the full Foreign libraries are also included (in hierarchical form). * The library function List.sortBy now uses a stable O(n log n) mergesort. * Numerous other small fixes, including revisions to the Haskell'98 standard. * The website is now hosted at haskell.org * Our CVS repository is also now hosted at cvs.haskell.org Regards, The nhc98 team at York ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: data vs. newtype, abstractly
Hal Daume III wrote: | there is a difference between | | (N undefined) `seq` () | | and | | (D undefined) `seq` () The question stated without its constructor. My guess is no. /K ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: data vs. newtype, abstractly
my guess is no too. An informal argument to that: imagine the datatype is abstract and no functions which act on it are exported .call it 'Type'. since there are no non-bottom values of this type that are exported, the only way to create them is with bottom as in: (undefined :: Type) (or an equivalant) which is equivalant for a newtype (N undefined :: Type) and for a data (undefined :: Type) note that there is no way to create the (D undefined) which is what lets you observe the difference. therefore you cannot tell the difference... Just my line of thought which led to saying 'no', interpret it as you will. John On Sun, Mar 09, 2003 at 12:58:49PM +0100, Koen Claessen wrote: Hal Daume III wrote: | there is a difference between | | (N undefined) `seq` () | | and | | (D undefined) `seq` () The question stated without its constructor. My guess is no. /K ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell -- --- John Meacham - California Institute of Technology, Alum. - [EMAIL PROTECTED] --- ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
broken Research Letters link
``Algebraic Conversions'', A mathematical paper introducing a generalisation of homomorphism of universal algebras. In Research Letters in the Information and Mathematical Sciences Vol 2, May 2001. (pub by Massey University New Zealand). see also, \verb|http://www.massey.ac.nz/~wwiims/rlims| This web link is broken. My apologies ... http://iims.massey.ac.nz/research/letters/volume2number1/02mills.pdf will get you there. I tested it just now, it works fine. Regards, Bruce. ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: data vs. newtype, abstractly
On Sun, 9 Mar 2003, Hal Daume III wrote: well, yes, but if you export: mkN :: Int - N mkD :: Int - D or something like that, then they'll still bea ble to tell the difference, right? Well, yes, but I don't. In fact the type in question is an MVar which my abstraction ensures is always defined. My question came up in the context of describing such an abstract type for users of the type. Like many others, I like to include actual Haskell code where appropriate in the documentation. It didn't seem right to commit there to either `data` or `newtype`. Perhaps I'll use: type Foo a -- abstract Does that disturb anyone? Any other ideas? Dean ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
RE: palm?
John Meacham wrote: This may be an intractable goal, but is any project out there anywhere close to a working haskell 98(ish) implementation for the Palm Pilot? There would probably have to be some compromises, like 16 bit Ints and perhaps some other restrictions, but i don't think its impossible to get some sort of lazy implementation to work on such a resource starved architecture so has anyone given it a shot? Here at Macquarie University we have done some work on this. Matthew Tarnawsky ported the nhc98 runtime to the Palm as part of his 2002 honours project working with myself and Dom Verity. With this port it's possible to compile programs on a desktop machine and load the bytecode onto a Palm for execution. There is a limited interface to the Palm GUI libraries. Having said that, there is much to be done. The current implementation has only been lightly tested and there are a number of design decisions that we want to revisit, particularly relating to how garbage collection works. We are starting to port the work to a recent version of nhc98 and are looking at some of these questions. We hope to have something for others to play with in a few months. Stay tuned to this list for an announcement. Cheers, Tony Sloane -- Senior Lecturer Dept of Computing, Macquarie University Sydney, Australia ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: data vs. newtype, abstractly
Dean Herington writes: : | My question came up in the context of describing such an abstract type for | users of the type. Like many others, I like to include actual Haskell | code where appropriate in the documentation. It didn't seem right to | commit there to either `data` or `newtype`. Perhaps I'll use: | | type Foo a -- abstract | | Does that disturb anyone? Any other ideas? That's pretty close to Haddock's approach. For example, see newtype N4 in http://www.haskell.org/haddock/Test.hs : An abstract newtype - we show this one as data rather than newtype because the difference isn't visible to the programmer for an abstract type. ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: Persistant (as in on disk) data
hello, I'm not convinced that the binary library should natively support cyclic data. I think that if saying: print x would not terminate, then there's no reason that puts bh x should terminate. I like to think of puts as a binary version of print. (That is, of course, unless the instance writer for the Binary/Show instances of the type of x is smart enough to not keep writing the same thing over and over again.) I would challenge the interested party to write a Show instance of String which wouldn't loop indefinitely on repeat 'x'. well, it is your choice to think of it as you like, but this is not what my original mail was about. i think the ability to make data persistant is a useful one and it should be as transperant to the programmer as possible. when i write something like: ones = 1 : ones i don't think of printing infinately many ones in memory and i don't see why i should start thinking of it that way just because i want to make the object persistant. after all, one can think of the disk as a verys low memory. If the user has some cyclic data structure and they want to be able to write it in binary form, it should be on their shoulders to do it correctly, not on the library's. why is that? i thought the whole point of having nice tools is that you don't need to write mindless stuff and concentrate on the important bits of your program. i don't have to worry much about sharing and cyclic data when i program in Haskell (i.e. it just happens), why should i suddenly start to worry about that if i want to make something persistant across executions of my program. So essentially, I believe 'deriving Binary' should work identically to 'deriving Show', except using a binary rep instead of a string rep. something like that could be useful, but with drift and the atrem library one can already do some of that. and the aterm library is a reasonably portable way to represent terms. this is definately not what i had in mind in my original post. it in Haskell, as presumbably sharing is not observable from within the language. this is why the deriving bit seems essential - the compiler can perform some magic. I assume you mean something like: let x = ...some really large structure... y = [x,x] in puts bh y then the size of what is written is |x+c| not |2x| for some small c? If so, then I don't believe this can be implemented in the language; it would have to be in the compiler. this is what i meant by compiler magic. I see this as unlikely of happening because it would mean that all compilers would have to implement this identically and some might not handle sharing the same manner. different implementations do not need to implement sharing in the same way. they need to understand a common format. i am not saying designing such a format is easy, in fact things like: nats = 0 : map (+1) nats seem tricky as they involve functions. but persitance is useful. in fact as a beginning i was hoping for something that works in say GHC, and won't be too hard to implement. actually i thought it might already exist, but i guess not. bye iavor ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
FFI Tutorial / Examples
Hi all, I may be being a bit dense about this, but I am having some trouble understanding how to use FFI, especially with respect to interfacing Haskell lists/arrays to C arrays. For example, say I have the C functions void foo (double *input, double *output, int N); double bar (double *input, int N); and I want to create an FFI interface and have the resulting type signatures be foo :: Array Int Double - Array Int Double bar :: Array Int Double - Double where the bounds of the arrays are (0,N-1), and both foo and bar are pure. I read through the FFI docs, but I am still confused about how to do this. Can anyone point me to an FFI tutorial, or some examples? I have a feeling that once I see some examples using lists and arrays that things will fall into place. Thanks. -- Matthew Donadio ([EMAIL PROTECTED]) ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: palm?
What about a port to Windows CE (i.e., for Pocket PC's). Or even better yet, hugs for Pocket PC! -Matt On Sunday 09 March 2003 11:27 pm, Tony Sloane wrote: John Meacham wrote: This may be an intractable goal, but is any project out there anywhere close to a working haskell 98(ish) implementation for the Palm Pilot? There would probably have to be some compromises, like 16 bit Ints and perhaps some other restrictions, but i don't think its impossible to get some sort of lazy implementation to work on such a resource starved architecture so has anyone given it a shot? Here at Macquarie University we have done some work on this. Matthew Tarnawsky ported the nhc98 runtime to the Palm as part of his 2002 honours project working with myself and Dom Verity. With this port it's possible to compile programs on a desktop machine and load the bytecode onto a Palm for execution. There is a limited interface to the Palm GUI libraries. Having said that, there is much to be done. The current implementation has only been lightly tested and there are a number of design decisions that we want to revisit, particularly relating to how garbage collection works. We are starting to port the work to a recent version of nhc98 and are looking at some of these questions. We hope to have something for others to play with in a few months. Stay tuned to this list for an announcement. Cheers, Tony Sloane ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Fw: palm?
- Original Message - From: Tony Sloane [EMAIL PROTECTED] To: Kenny Lu Zhuo Ming [EMAIL PROTECTED] Sent: Monday, March 10, 2003 11:13 AM Subject: RE: palm? Hi Kenny, How about PocketPC? any porting is done on that? No, we have not done any work on Haskell on the PocketPC platform. Tony __ Do You Yahoo!? Promote your business from just $5 a month! http://sg.biztools.yahoo.com ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
GHC Error Message.
Hi,
Could someone please explain to me why the
following error message happen:
When I load the following code into GHC I get an
error message:
code:
---
data AParser String = AP
{apapply::([String]-[(String,[String])])}
instance Monad AParser where return
v = AP (\inp -
[(v,inp)]) (AP p) = f = AP (\inp -
concat [ apapply (f v) inp1 | (v,inp1) - p inp])
---
error:
---
Inferred type is less polymorphic than
expected Quantified type variable
`b' is unified with another quantified type variable `a'
When trying to generalise the type inferred for
`=' Signature
type: forall a1
b1.
AParser a1 - (a1 - AParser b1) - AParser
b1 Type to generalise: forall a1
b1.
AParser a1 - (a1 - AParser b1) - AParser b1 In
the instance declaration for `Monad AParser'Failed, modules loaded:
none.
---
But when I create thetype synonym
type Stack = [String]
data AParser String = AP {apapply::(Stack - [(String,Stack)])}
and use Stack instead of [String], GHC does not complain???
Thanks.
Mansour.
Alternatives to finalization
As the result of a conversation on haskell-gui, I have tried to implement the disallocation of resources when a stream is garbage collected. To explain myself: I have a function f :: IO [a] which returns a lazy stream after allocating some resource to feed it (say installing a callback). I wish that the resource could be disallocated when it's no longer used. I did the obvious implementation with Weak.addFinalizer; results are encouraging but not completely satisfying; the scheme I used is: f = do allocateResource l - makeTheStream addFinalizer l (disallocateResource) return l The problem is that if no memory is allocated, no garbage collection happens; of course finalization is not guaranteed, as the manual states. Another alternative is to make f return an esplicit close stream action: f :: IO ([a],IO ()) Is anyone willing to explain me other alternatives if there are, or to tell me that there aren't? Thanks for attention Vincenzo ___ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
