March 2001 - Haskell - Haskell.org

Re: the constant functor
by Tobias Haeberlein 27 Mar '01

27 Mar '01

> What is wrong with: > > class Functor ConstInt where > map f (Const n) = Const n Ups - absolutely nothing. I actually tried it with data ConstInt a = Int and didnt manage to make this an instance of class Functor. Sorry for giving the wrong example. -Tobi -- GMX - Die Kommunikationsplattform im Internet. http://www.gmx.net

1 0

the constant functor
by Tobias Haeberlein 27 Mar '01

27 Mar '01

I am trying to make all polynomial functors (in the categorical sense) an instance of the class Functor. Consider a datatype (corresponsing to a constant functor): data ConstInt a = Const Int ConstInt is clearly a functor in the categorical sense, but is 'ConstInt' also a functor in Haskell?? Any ideas how to make 'ConstInt' an instance of class Functor? -Tobi -- GMX - Die Kommunikationsplattform im Internet. http://www.gmx.net

1 0

Announce: Haskell libpq binding
by Wojciech Moczydlowski, Jr 23 Mar '01

23 Mar '01

The Haskell libpq (client-side PostgreSQL programming library) binding is now available to download, along with a simple DBI for Haskell, similar to this in Perl, allowing a programmer to write a database-independent code. It can be found at http://www.astercity.net/~khaliff/haskell/dbi/dbi.tgz. To compile, KDirect (http://www.astercity.net/~khaliff/kdirect) and the latest version of QForeign (http://sourceforge.net/projects/qforeign) is needed. It should compile both under ghc and nhc, yet only ghc was tested. It is no end-user product, though - there is no "install" rule in Makefile and Makefile editing is necessary, I'm afraid. If someone finds it useful or has any suggestions, I would love to hear them. Wojciech Moczydlowski, Jr

1 0

Re: Question concerning ftp and GHC binaries for HP-UX
by Bark Fook 23 Mar '01

23 Mar '01

> Message: 1 > From: "ADAMS,RICHARD (Non-HP-Roseville,ex1)" > <richard_adams(a)non.hp.com> > To: "'haskell(a)haskell.org'" <haskell(a)haskell.org> > Subject: Question concerning ftp and GHC binaries > for HP-UX > Date: Wed, 21 Mar 2001 12:24:15 -0700 > > I would like to download the GHC binaries to our HP > 9000 machine (HP-UX > 11.0), but have access only to ftp (i.e., no Web > browser is available). > Does anyone know what ftp address to use? Also, > does anyone know whether > the GHC binaries for the HP-UX operating system will > work on HP-UX 11.0? > > I am not sure whether it is relevant, but I use > Reflection terminal > emulation to telnet from my PC to the HP 9000 > machine. Truly 'hi-tech' :) . > > Thank you. > > Sincerely, > > Richard E. Adams > Softmatrix, Inc. > Roseville, CA > Email: richard_adams(a)non.hp.com > I encountered the same problem of downloading with ftp. However, even if you succeeded in downloading, I guess it would not work as we wish:(. The system I use is HP-UX 11.00 (64-bit) HPPA 2.0. And I downloaded the version 4.08.2 for hppa1.1-hp-hpux with HTTP. It ran (without explicit errors) and output sth when input sth.hs. However, each time when I ran the sth, I got core dump. I tried to recompile the compiler (or even Happy), of course, failed with the same symptom (or unHappy). If I know anyone has successfully run GHC without incurring core dumps in HP-UX 11.00 (64-bit), I'll be very happy if Happy works too:). If I have enough time, I wish I could port it to HP-UX 11.00 (64-bit). I'm very glad to know if there exists somebody who will aid me or play together with me over 64-bit ghc for 64-bit HPUXes. Should I attack the problem from HBC or nhc98? One more bad news, SMLNJ works on HP-UX 10.20, not on HP-UX 11.00, either:-(. I've tried and failed too. One more good news, Hugs98-Feb2001 does work in HP-UX 11.00 (64-bit). I swear, where only very few tweaks are needed. But I guess it's running in 32-bit mode:-). The last kisstion: Can I build ghc from Hugs, my god? __________________________________________________ Do You Yahoo!? Get email at your own domain with Yahoo! Mail. http://personal.mail.yahoo.com/

2 1

url update for Asperti & Longo: "Categories, Types and Structures"
by Jens-Ulrik Petersen 23 Mar '01

23 Mar '01

Hi Frank, Thanks for making <http://www.cs.uu.nl/people/franka/ref.html>. Good idea! "Frank Atanassow" <franka(a)cs.uu.nl> writes: > [1] Andrea Asperti and Giussepe Longo. Categories, Types and Structures. An > introduction to Category Theory for the working computer > scientist. MIT Press, 1991. > URL: http://www.dmi.ens.fr/users/longo/download.html It seems ENS's DMI bifurcated... the current url is now http://www.di.ens.fr/users/longo/download.html Maybe you could update the link on your page too. Thanks, Jens

1 0

Re: modules and re-export
by Sigbjorn Finne 21 Mar '01

21 Mar '01

Peter Thiemann thiemann(a)informatik.uni-freiburg.de writes: > > I have a little question about the following two modules. Suppose you > want to write your own variant of the prelude that redefines a couple > of names but leaves all the rest unchanged. The Haskell report says > that the following should work: > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > module BUG2A (module BUG2A, module Prelude) where > > import Prelude hiding (head) > > head = "HEAD" > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .... > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > module BUG2B where > > import qualified Prelude > import BUG2A > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > Unfortunately, this does not behave as (I think) it should: > > Reading file "BUG2B.hs": > Parsing..................................................................... ... > ERROR "BUG2B.hs": Entity "head" imported from module "BUG2A" already > defined in module "Prelude" > > However, this should be legal from my reading of the report. Hi Peter, yep, that's right, and it is a known wrinkle in Hugs' implementation of modules. I submitted a source fix which addresses just this a couple of weeks ago, http://haskell.cs.yale.edu/pipermail/hugs-bugs/2001-March/000184.html hopefully it will be included in future releases of Hugs98. hth --sigbjorn

2 1

Question concerning ftp and GHC binaries for HP-UX
by ADAMS,RICHARD (Non-HP-Roseville,ex1) 21 Mar '01

21 Mar '01

I would like to download the GHC binaries to our HP 9000 machine (HP-UX 11.0), but have access only to ftp (i.e., no Web browser is available). Does anyone know what ftp address to use? Also, does anyone know whether the GHC binaries for the HP-UX operating system will work on HP-UX 11.0? I am not sure whether it is relevant, but I use Reflection terminal emulation to telnet from my PC to the HP 9000 machine. Truly 'hi-tech' :) . Thank you. Sincerely, Richard E. Adams Softmatrix, Inc. Roseville, CA Email: richard_adams(a)non.hp.com

1 0

Re: modules and re-export
by Matthias Fischmann 21 Mar '01

21 Mar '01

Peter Thiemann <thiemann(a)informatik.uni-freiburg.de> writes: > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > module BUG2A (module BUG2A, module Prelude) where > import Prelude hiding (head) > head = "HEAD" > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > module BUG2B where > import qualified Prelude > import BUG2A > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > Unfortunately, this does not behave as (I think) it should: > [...] ghc-4.08.1 compiles it without complaining. A Hugs98 bug? -Matthias

1 0

Re: Coroutines
by Richard Uhtenwoldt 21 Mar '01

21 Mar '01

Andreas Gruenbacher writes: >It's not what I had in mind, though. Simon's MVars (in the Awkward Squad) >come pretty close, but they're still not the sort of (cooperative) >multitasking that I'm thinking of. I hope I'm not being too fussy, but seems to me that the CVar is what is needed, not the MVar: >main= > newCVar >>= \l0 -> > newCVar >>= \l1 -> > newCVar >>= \l2 -> > forkIO readInputLineAtATime l0 >> > forkIO printHeader "silly header" l0 l1 >> > forkIO numberLines 0 l1 l2 >> > printOutputLineAtATime l2 (untested code.)

1 0

GHC Mingw32 build
by Mike Thomas 20 Mar '01

20 Mar '01

Hi all.. What is the recommended way of making the Mingw32 build of GHC and all associated tools, eg HDirect, Green-card etc from the CVS? Cheers Mike Thomas

1 0