November 2007 - Haskell-Cafe

Haskell code in Wordpress
by Paulo J. Matos 25 Nov '07

25 Nov '07

Hi all, I'm curious about the best way to typeset haskell code in a wordpress blog. Using blockquote removes all indentation. :-( Cheers, -- Paulo Jorge Matos - pocm at soton.ac.uk http://www.personal.soton.ac.uk/pocm PhD Student @ ECS University of Southampton, UK

6 6

problems building ycr2js
by Thomas Hartman 25 Nov '07

25 Nov '07

OK, I struggled through the instructions at http://haskell.org/haskellwiki/Yhc/Javascript/Users_guide#Downloading and am getting tripped up at (cd src/translator/js; make all install) any advice? ... blah blah blah.... ghc --make -i../../../depends/filepath splitter.hs -o /home/thartman/haskell-installs/yhc-install/yhc/src/translator/js/inst\ /bin/splitter [1 of 4] Compiling System.FilePath.Version_0_11 ( ../../../depends/filepath/System/FilePath/Version_0_11.hs, ../../../depend\ s/filepath/System/FilePath/Version_0_11.o ) [2 of 4] Compiling System.FilePath ( ../../../depends/filepath/System/FilePath.hs, ../../../depends/filepath/System/FilePat\ h.o ) [4 of 4] Compiling Main ( splitter.hs, splitter.o ) Linking /home/thartman/haskell-installs/yhc-install/yhc/src/translator/js/inst/bin/splitter ... echo > W3C/addtags.idl for tag in SUB SUP SPAN BDO I B U S \ STRIKE BIG SMALL EM STRONG DFN CODE \ SAMP KBD VAR CITE ACRONYM ABBR \ DD DT NOFRAMES NOSCRIPT ADDRESS CENTER ; do \ ltag=`echo ${tag:1} | tr [:upper:] [:lower:]` ; \ echo " interface HTML${tag:0:1}${ltag}Element : HTMLElement {" >> W3C/addtags.idl ; \ echo " };" >> W3C/addtags.idl ; \ echo >> W3C/addtags.idl ; \ done /bin/sh: Syntax error: Bad substitution make: *** [W3C/addtags.idl] Error 2

2 5

emacs haskellers: r-stripping files becomes popular
by Valery V. Vorotyntsev 25 Nov '07

25 Nov '07

Add the following lines to your ~/.emacs: ------- BEGIN OF ELISP CODE ------- ;(global-set-key (kbd "<f9> s") 'delete-trailing-whitespace) (defun delete-trailing-whitespace-if-confirmed () "Delete all the trailing whitespace across the current buffer, asking user for confirmation." (if (and (save-excursion (goto-char (point-min)) (re-search-forward "[[:space:]]$" nil t)) (y-or-n-p "Delete trailing whitespace? ")) (delete-trailing-whitespace))) (add-hook 'before-save-hook 'delete-trailing-whitespace-if-confirmed) ------- END OF ELISP CODE ------- Have fun! -- vvv

6 9

is there a more concise way to generate helper functions for a datatype built on records?
by Thomas Hartman 25 Nov '07

25 Nov '07

I think I'm running into more or less the same issue discussed at http://bloggablea.wordpress.com/2007/04/24/haskell-records-considered-grung… Just wondering if I missed anything, or if any of the ideas considering better records setter/getters have been implemented in the meantime. t. ************** -- Is there any way to do the following more concisely? -- Seems like a lot of boilerplate data GameState = GameState { guesses :: Int, userHighScores :: UserHighScores, answer :: Maybe Int } deriving Show -- State Helpers --------------------------------------- modGuesses f gSt = _set_guesses ( (f . guesses) gSt) gSt modUserHighScores f gSt = _set_userHighScores ( (f . userHighScores) gSt) gSt modAnswer f gSt = _set_answer ( (f . answer) gSt) gSt _set_guesses new gSt = gSt {guesses=new} _set_userHighScores new gSt = gSt { userHighScores=new } _set_answer new gSt = gSt { answer=new }

5 4

nhc vs ghc
by brad clawsie 25 Nov '07

25 Nov '07

can anyone provide a concise list of the major differences between nhc98 and ghc? for example, can i build a cabal package with nhc98? i get that ghc and nhc98 are not interchangeable, otherwise i am not sure thanks

7 7

been scouring through the Haskell prelude to no avail ...
by Galchin Vasili 24 Nov '07

24 Nov '07

Hello, Is there any predefined datatype that can be used to represent a two byte value? Kind regards, Vasili

2 1

Re: [Yhc] Re: [Haskell-cafe] yhc install fails
by Thomas Hartman 24 Nov '07

24 Nov '07

Thanks, that worked. I think there's some weird issue with the way the build happens that requires you to do rm -rf yhc; darccs get http://...yhc for a truly "fair" build to take place. I saw something in a bug report about how things get cached. That means that an ok from a buildbot doesn't mean that the build is really ok. It occurs to me that if it's possible to get the buildbot to do rm -rf and darcs re-checkout that might be worth doing, until the issues with stuff getting cached get resolved. But maybe that's smiting a mosquito with a flamethrower. thomas. 2007/11/22, Thomas Shackell <shackell(a)cs.york.ac.uk>: > Apologies, I broke this when I fixed the getArgs bug. It's actually just > a build problem, Storable needs to be built before C/String. I didn't > notice it because it only happens with a fresh (uncompiled) copy of yhc. > Anyway fix pushed. > > > Thanks > > Tom > > > > > Neil Mitchell wrote: > > Yhc people: > > > > On Nov 21, 2007 8:46 PM, Thomas Hartman <tphyahoo(a)gmail.com> wrote: > >> I'm having the devil of a time getting yhc to install. > >> > >> http://hpaste.org/4028 > >> > >> or for posterity > >> > >> root@none:~/yhc-install/yhc>scons > >> > >> ... blah blah blah... > >> > >> Compiling PreludeAux ( src/packages/yhc-base-1.0/PreludeAux.hs ) > >> YHC_build(["src/packages/yhc-base-1.0/Foreign/Util.hbc"], > >> ["src/packages/yhc-base-1.0/Foreign/Util.hs"]) > >> inst/bin/yhc --core --cpp -c src/packages/yhc-base-1.0/Foreign/Util.hs > >> Compiling Foreign.Util ( src/packages/yhc-base-1.0/Foreign/Util.hs ) > >> YHC_build(["src/packages/yhc-base-1.0/Foreign/C/String.hbc"], > >> ["src/packages/yhc-base-1.0/Foreign/C/String.hs"]) > >> inst/bin/yhc --core --cpp -c src/packages/yhc-base-1.0/Foreign/C/String.hs > >> Error: File not found, Foreign.Storable > >> Reason: imported from Foreign.C.String > >> Looked in: > >> /root/yhc-install/yhc/src/packages/yhc-base-1.0/ > >> /root/yhc-install/yhc/inst/lib/yhc/packages/yhc-base/1.0 > >> scons: *** [src/packages/yhc-base-1.0/Foreign/C/String.hbc] Error 1 > >> scons: building terminated because of errors. > >> > >> > >> root@none:~/yhc-install/yhc>ghc --version > >> The Glorious Glasgow Haskell Compilation System, version 6.8.1 > >> > >> advice? > >> > >> thomas. > >> _______________________________________________ > >> Haskell-Cafe mailing list > >> Haskell-Cafe(a)haskell.org > >> http://www.haskell.org/mailman/listinfo/haskell-cafe > >> > > _______________________________________________ > > Yhc mailing list > > Yhc(a)haskell.org > > http://www.haskell.org/mailman/listinfo/yhc > >

1 0

Call external program and get stdout
by Maurício 24 Nov '07

24 Nov '07

Hi, How can I call a program (like, for instance, 'grep text *') and get the standard output? All actions I found (executeFile, system) do not give me the output of the program. Thanks, Maurício

5 6

Unix (Posix) low-level device driver functionality?
by Galchin Vasili 24 Nov '07

24 Nov '07

Hello, I am seriously trying to push the mainstream computer industry. I am a kernel developer for POSIX OS's (e.g. Linux) and Windows. I would at the very least be able to write "test"/correctness software in Haskell where I am able to open Unix/Windows drivers and test storage firmware. The possibility exists in Houston to do this .. I want FPLs (in particular Haskell) to strut their "stuff" even on humble stubble stuff like firmware verification. In any case, it seems like the GHC documentation allows "raw driver I/O"but when I look at the actual GHC 6.8.1 libraries I don't see low level driver functionailty. Kind regards, Vasya

3 2

Composing monads
by Maurício 24 Nov '07

24 Nov '07

Hi, If I have two computations a->IO b and b->IO c, can I join them to get an a->IO c computation? I imagine something like a liftM dot operator. Thanks, Maurício

9 10