- Haskell-Cafe - Haskell.org

Re: character syntax
by C.Reinke 08 Feb '02

08 Feb '02

> > Second, this argument would be easier to accept if there in fact were > > an equally innovative tool capable of providing all the editing > > goodies Emacs normally does, for Haskell. But I don't know of one, > > even now, 10 years or so after Haskell's birth. Well, it was one of the happier accidents in programming language history that Lisp was implemented and released before it received a concrete syntax. But Haskell isn't built on s-expressions. Simon M. says that syntax highlighting for Haskell is quite doable, and Haskell modes for other editors seem to support that claim, as others have pointed out. So I wonder whether what once was a very innovative tool is in the process of becoming just another legacy. I'm relatively happy with my editor, as far as editors go. What features (editing goodies) are you referring to? > .. There was recently a PhD position advertised > on the list in the area of refactoring functional programs; I'd be > surprised if whoever does that doesn't eventually end up with a GUI > (whether inherited from somewhere else or written as part of the project). Postdoc, actually. Although, once we have someone in place on that position, it would also be nice to complement our project with a PhD candidate working on refactoring in another functional language (Erlang, say), sufficiently different from both Haskell and from the oo/imperative languages for which refactoring support is now becoming more and more common. As for innovation in program editing, the idea (and problem) is not so much awareness of lexical syntax (syntax highlighting) or editing at the level of abstract syntax (for those with unhappy memories of structure editors: we want syntax-aware editors, not syntax-directed ones), but making editing tools more aware of language semantics (static semantics, at least). As for GUIs, we would like to avoid getting into editor wars, and we would rather spend our time on the refactoring side than on implementing YAE, yet another editor. Simon and I happen to use the same YFE (your favourite editor), but we know that there's a big group of Haskell users who wouldn't be very pleased if they had to switch from TOE (that other editor) to YFE, just to make use of our refactoring tool (note that I'm silently ignoring AOE, all other editors here;-). And both groups would be very unhappy if they had to go from their own powerful, all-purpose editor to whatever we could hack up while we should be doing other things. It's too early to say how things will pan out in the end, but we'd like to start with a separate refactorer, with a well-defined interface, and bindings to that interface for both YFE and TOE. As you suggest, the refactorer will have rather more information about the program than might easily be displayed via YFE/TOE/ETC, so we might need a separate GUI at some point. We'll see.. IYSWIM?-) Claus Refactoring Functional Programs http://www.cs.ukc.ac.uk/people/staff/sjt/Refactor/

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RE: character syntax
by Simon Marlow 08 Feb '02

08 Feb '02

> itz> All this taken together, I mean, _really_, is the lexical > itz> structure of Haskell a botch, or what? > > Jon> No. Innovative. All the problems described in this thread reflect > Jon> unwarranted assumptions inherited in emacs. It's plainly possible > Jon> to parse Haskell, and not hard either. > > First, parsing of a complete program (eg. by a compiler) is quite > different from parsing a buffer that is being edited by a human. The > latter is hard, even for fairly well-specified languages. > Irregularities only make it harder. For syntax highlighting you only need to lexically analyse the buffer, not parse it. Haskell's lexical syntax is parseable by regular expressions, which means it shouldn't be hard to plug a syntax highlighter for Haskell into just about any editor. I don't understand why you say that parsing a buffer being edited by a human is hard - perhaps doing incremental lexing is slightly harder than whole-file lexing, but not that much harder. The "state" of a Haskell lexer can be represented with a little trickery by an integer, so it isn't hard to cache the lexer's state at the beginning of each line. I did this once as an experiment when I added Haskell syntax highlighting to one of the KDE editors (I forget which). The problem is not Haskell, it's emacs. Emacs's syntax highlighting has fairly deeply-wired-in assumptions about C-like languages (eg. last I looked you still couldn't support nested comments properly in font-lock). Cheers, Simon

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win32 stand alone binaries?
by Brett Morgan 08 Feb '02

08 Feb '02

Is it possible to build win32 stand alone binaries using cygwin hosted ghc tools? I know in some ways this is sacriligous to the many unix die hards out there (myself included) - but some of the algorithm's i'm contemplating could possibly turn out to be useful for the "unwashed masses" if a wimp binary could be produced. And I really don't want to go back to c++ for reasons i'm sure most people here are familiar with... brett -- email: Brett.Morgan(a)uts.edu.au phone: 0416-241-898 magic: 153 2 8 105 225 You just come along with me and have a good time. The Galaxy's a fun place. You'll need to have this fish in your ear. Q: What is the shortest lie in computing? A: It works. -- Matthias Felleisen

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Re: compiling hdirect
by Sigbjorn Finne 05 Feb '02

05 Feb '02

Johannes Goetx info(a)polirami.de writes: > ... > gcc -O -mno-cygwin -mwin32 -c mkNativeInfo.c -o mkNativeInfo.o > mkNativeInfo.c:0: malformed option `-D __WIN32__-DWIN32' ... > > malformed option `-D __WIN32__-DWIN32' > > Where can I change this? I could not find a file containing this > option string. Hi, you're using a version of gcc with a broken 'specs' file. Locate the specs file inside your cygwin(?) install tree & change the portion of the "*cpp:" section which expands -mwin32 and -mno-cygwin to the following: %{mwin32|mno-cygwin:-DWIN32 -D_WIN32 -D__WIN32 -D__WIN32__ -DWINNT } i.e., add a space after -DWINNT and the '}' This issue will soon go away, as the use of -mwin32 in GHC's fptools/ tree is in the process of being nuked. hth --sigbjorn

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Re: using composition with multiple argument functions
by Ashley Yakeley 03 Feb '02

03 Feb '02

[Moved to Cafe] At 2002-02-02 17:42, Dean Herington wrote: >With `h1 f g = f # g` and the type >declaration for h1, the compiler sees that f1 and g1 must be used at the >same type. With `h1 = f1 # g1`, that connection is missing. Yes. Haskell cannot be sure that the last instance declaration is the one it wants, because, even though it would work, there might be other possible instance declarations that could apply. Here's a simpler example: -- class C f where foo :: f -> Bool instance C (Bool->Bool) where foo f = f True instance C (Int->Int) where foo f = False f :: Bool f = foo id -- Either instance declaration would work, but Haskell needs one unambiguously for the general type of 'id'. You can fix it by restricting the type of 'id': -- f :: Bool f = foo (id :: Int -> Int) -- >So I guess my `Composable` class example can't work in general. Maybe, maybe not. -- Ashley Yakeley, Seattle WA

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compiling hdirect
by Johannes Goetz 02 Feb '02

02 Feb '02

Hi! Just tried to compile hdirect... ;-) $ make boot make -C src boot && make -C src all make[1]: Entering directory `/home/Administrator/fucker/hdirect/src' rm -f Version.hs echo "--Automatically generated" > Version.hs echo "module Version where" >> Version.hs echo "" >> Version.hs echo "pkg_name :: String" >> Version.hs echo "pkg_name = \"HaskellDirect (ihc.exe)\"" >> Version.hs echo "pkg_version :: String" >> Version.hs echo "pkg_version = \"snapshot 020202\"" >> Version.hs gcc -O -mno-cygwin -mwin32 -c mkNativeInfo.c -o mkNativeInfo.o mkNativeInfo.c:0: malformed option `-D __WIN32__-DWIN32' make[1]: *** [mkNativeInfo.o] Error 1 make[1]: Leaving directory `/home/Administrator/fucker/hdirect/src' make: *** [boot] Error 2 malformed option `-D __WIN32__-DWIN32' Where can I change this? I could not find a file containing this option string. Thanks, Johannes

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Re: functions not in type classes
by Yoann Padioleau 02 Feb '02

02 Feb '02

"Cagdas Ozgenc" <co19(a)cornell.edu> writes: > Greetings. > > Why does Haskell let you write functions that are not a part of type class? > For example instead of the goal of type class is to allow overloading of function, so for example id x = x is not subject to overloading => no use to put it in a type class. > > elem :: Eq a => a -> [a] -> Bool > map :: (a -> b) -> [a] -> [b] > > class Container a where > elem :: Eq b => b -> a b -> Bool > map :: (b -> c) -> a b -> a c > > would define methods that can work on all containers, and create a > discipline to write more reusable and generic functions. yes, that's right that map and elem could be put in a type class, but that's hard and require more advanced feature of haskell (here you use constructor class but you need more : multi-parameter class, ....) see http://www.cse.ogi.edu/~mpj/fds.html. > > Thanks > > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > -- Yoann Padioleau, INSA de Rennes, France, Opinions expressed here are only mine. Je n'écris qu'à titre personnel. **____ Get Free. Be Smart. Simply use Linux and Free Software. ____**

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monad thinking process
by Cagdas Ozgenc 25 Jan '02

25 Jan '02

Greetings. I have very little experience with monads. However my first impression is that there is too much thinking process involved in programming with monads, and it is very time consuming, at least for a beginner like myself. I don't know how productivity changes once you get used to programming with them. Also, I have serious concerns about the maintenance of programs written in monadic style. Since there is too much plannning overhead, it doesn't seem suitable for evolutionary software development process. What do monad experts think? What do you think of code readability? How easy is it to prove that programs written with monads are correct? How does changing one function affect other functions, in terms of maintenance? Thanks

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Re: Monad composition
by John Hughes 25 Jan '02

25 Jan '02

Andre W B Furtado wrote: >Well, it's also possible to interchange data between these two monads by: > >unsafeIOToST :: IO a -> ST s a >stToIO :: ST s a -> IO a > >Can anyone tell the possible problems related to >unsafeIOToST? >^^^^^^ Probably in the same manner as with unsafePerformIO: it can break referential transparency. Indeed, unsafePerformIO m = runST (unsafeIOToST m) so they're just as unsafe as each other. John Hughes

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Dynamic linking of Haskell modules?
by senganb＠ia.nsc.com 25 Jan '02

25 Jan '02

I'd like to be able to dynamically load Haskell code from a "plugin" binary file into a Haskell application, just as I can dynamically load .so files into a C application. Since ghci does this, I thought I could copy its implementation but after looking into it, it's very complicated. I notice that OCaml can do this (http://algol.prosalg.no/~malc/scaml/) The only simple solution I can think of is to use FFI to export the objects in the .so file as following the C interface, and then importing them into the main Haskell application as "C functions", but the extra marshalling is ugly. Has anyone solved this problem? Are there any plans to support this in the future in ghc or a third party library? Sengan

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