Re: -pgm option syntax
Jens Petersen [EMAIL PROTECTED] writes:
Jens Petersen [EMAIL PROTECTED] writes:
It would be good if ghc would at like give a better error
message when an empty cmd is passed to -pgmX.
Rather I think it should abort rather than forking an empty
command...
How about something like the following untested patch to
this effect? (In the ideal world it would test that c is a
valid program flag, but anyway...)
Jens
2002-02-20 Jens Petersen [EMAIL PROTECTED]
* compiler/main/SysTools.lhs (setPgm): Abort when a null cmd is
passed to a -pgmX option.
Index: SysTools.lhs
===
RCS file: /cvs/fptools/ghc/compiler/main/SysTools.lhs,v
retrieving revision 1.70
diff -u -r1.70 SysTools.lhs
--- SysTools.lhs2002/02/16 19:39:51 1.70
+++ SysTools.lhs2002/02/20 13:15:44
@@ -417,6 +417,7 @@
-- The string is the flag, minus the '-pgm' prefix
-- So the first character says which program to override
+setPgm ([c]) = throwDyn (UsageError (-pgm ++ [c]: no CMD argument))
setPgm ('P' : pgm) = writeIORef v_Pgm_P pgm
setPgm ('F' : pgm) = writeIORef v_Pgm_F pgm
setPgm ('c' : pgm) = writeIORef v_Pgm_c pgm
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Typing RULES
Hi!
Ghc seems to have some problems in inferring the most general types of
RULES pragmas. The bug was not present in 5.02.1 but shows up in a cvs
version checked out yesterday.
Here's the problem:
Consider the following example from the user's guide:
{-# RULES
map/map forall f g xs. map f (map g xs) = map (f.g) xs
#-}
When I compile with -ddump-rules I get the following rule:
map/map __forall {@ b
@ b
@ a
f :: (b - b)
g :: (a - b)
xs :: [a]}
GHC.Base.map @ b @ b f (GHC.Base.map @ a @ b g xs)
= GHC.Base.map @ a @ b (GHC.Base.. @ b @ b @ a f g) xs ;
(And it also turns out this rule is listed among the imported rules, not
the local ones, which is a bit confusing.)
The rule says that f must have type b - b for some b. This is clearly Bad
as the matching algorithm also matches types and the rule will not be
fired in all the cases it should.
When I add a type signature for f then g get type b - b. In order to get
the desired behaviour I have to add type signatures to both f and g.
I hope this is easy to fix.
Cheers,
/Josef
PS. Would it be possible to add a -fwarn-pragma which warns when a pragma
is ignored? It is quite frustrating when some rules are silently ignored
and you keep wonder why the rules don't fire. I guess I've learnt to use
-ddump-rule the hard way...
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Re: Congrats to Mandrake
Ashley Yakeley [EMAIL PROTECTED] writes: At 2002-02-19 14:13, Duncan Coutts wrote: So what I mean is, can we have links to more binaries than just Red Hat? Debian, Mandrake, FreeBSD. (I know these's SuSE) Seconded. I'm not sure what the point would be, if they are in the distributions anyway? Isn't it better to install them by apt-get or up2date or whatever? (In fact, I had almost thought manually downloading packages a thing of the past, but then the IT department insisted on Red Hat) -kzm -- If I haven't seen further, it is by standing in the footprints of giants ___ Glasgow-haskell-users mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
RE: Importing a reference to a non-function entity.
What is the politically correct way using the FFI and ghc5.03 (which I have just managed to compile from CVS) to import an externally defined object (not a function)? I have a source file containing the line foreign label default_options defaultOptions :: CString.CString for which ghc5.03 complains about Warning: foreign declaration uses deprecated non-standard syntax, but which works anyway. However in my attempt to be a good little ghc user, I try instead foreign import default_options defaultOptions :: CString.CString (after deciphering with difficulty the Postscript version of the FFI document on this screen) but still get the deprecated warning. Then I try foreign import ccall default_options defaultOptions :: CString.CString I believe you meant to say foreign import ccall default_options defaultOptions :: CString.Cstring :-) (see the latest FFI addendum at http://www.cse.unsw.edu.au/~chak/haskell/ffi/) Cheers, Simon ___ Glasgow-haskell-users mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
RE: Data constructors and pattern matching
It seems to me that it might be very useful for a module to export the
pattern matching operators for a datatype without exporting the
constructors. Suppose we have
data A = X {a::Int, b::Float}
And we want to maintain the invariant that b is a floating-point
representation of a. So normally we would have to use a completely
abstract datatype, and provide constructors and destructors. But in
this case, it would actually make sense to provide the
pattern-matching
operator X, but not the data constructor X. So I think it
would be good
to separate these in the module export syntax.
What's wrong with
module M (A, a, b) where { ... }
?
Simon
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RE: Congrats to Mandrake
Jim Farrand [EMAIL PROTECTED] wrote: both hugs and ghc in their Linux distro *as standard*. This could significantly help Haskell takeup amongst the unwashed masses. :-) Well, same applies for FreeBSD. And Debian. So what I mean is, can we have links to more binaries than just Red Hat? Debian, Mandrake, FreeBSD. (I know these's SuSE) It may just seem like clutter on the download page but it would help users and as much as anything else it shows some apreciation for the packagers who track the releases so well. Oops! Looks like I added the FreeBSD packages to my local copy of the web pages and forgot to copy it up to the web site. Sorry about that. I'll add links to the Mandrake packages while I'm there. Could someone who is Debian-compliant tell me where I should be pointing for Debian packages? Cheers, Simon ___ Glasgow-haskell-users mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: Congrats to Mandrake
[EMAIL PROTECTED] (Ketil Z. Malde) writes: I'm not sure what the point would be, if they are in the distributions anyway? Isn't it better to install them by apt-get or up2date or whatever? (In fact, I had almost thought manually downloading packages a thing of the past, but then the IT department insisted on Red Hat) If I, a developer, wrote a program, and some distributions included it (while others didn't), I would want to acknowledge and thank them in public. If I, a potential customer choosing among Linux distributions, liked to use a program, and I saw on the program home page that so-and-so distributions included the program, I would arrange my preference accordingly. If I, an absent-minded user, heard about some great program from my friends, and saw on the program home page which distributions included it, I might realize Gosh, *my* distribution CD already has it! and save some download and install effort. Remember, I am absent-minded, so I wouldn't know what's on my CD unless someone stick it on my face. :) I probably don't need hyperlinks; I just need to know if my distribution includes it or not. ___ Glasgow-haskell-users mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: i368-pc-os2-emx port
Simon Marlow [EMAIL PROTECTED] writes: On the other hand, you'd need something like mingw for OS/2 - does such a beast exist? The substring emx refers to an OS/2 version of gcc and libraries that make OS/2 look really like Unix from the programmer's point of view. (It probably even pre-dates cygwin.) I have two encouraging stories to tell. First, for a school assignment, I wrote an OpenGL program on emx, then ported it to school's Solaris+Mesa ten minutes before the deadline --- where porting meant removing #include os2.h. Second, I wrote a program that used tcpip sockets on Unix, then merely recompiled it on emx to use it on OS/2 as well. ___ Glasgow-haskell-users mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: Congrats to Mandrake
On Wed, Feb 20, 2002 at 03:45:15PM +0200, Lauri Alanko wrote: On Wed, Feb 20, 2002 at 01:37:52PM -, Simon Marlow wrote: Could someone who is Debian-compliant tell me where I should be pointing for Debian packages? http://ftp.debian.org/debian/pool/main/g/ghc5/ Though of course any debian user should just be able to say apt-get install ghc5 to get the latest package from the nearest mirror... Better: http://packages.debian.org/testing/devel/ghc5.html http://packages.debian.org/unstable/devel/ghc5.html --Dylan Thurston msg03123/pgp0.pgp Description: PGP signature
Haskell 98 Report
Is the revised Haskell98 report going to be put in its proper place on the web site any time soon? As it is, it is sitting off to the side while the old Report sits in the seat of honor. David Feuer ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Final CFP : FLOPS'02 / ASIA-PEPM'02
=== The submission deadline for ASIA-PEPM'02 and FLOPS'02 has ben extended until March 8, 2002. === FINAL CALL FOR PAPERS ASIAN Symposium on Partial Evaluation and Semantics-Based Program Manipulation http://www.comp.nus.edu.sg/asia-pepm02 International Symposium on Functional and Logic Programming http://www.ipl.t.u-tokyo.ac.jp/FLOPS2002/ Aizu, JAPAN, September 12-17 2002 *** IMPORTANT DATES: Submission Deadline: March 8, 2002 Notification:May 21, 2002 Final Version: June 25, 2002 Conferences: September 12-17, 2002 *** ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
RE: Haskell 98 Report
I don't want to do that until its finished! Which I earnestly hope will be soon. Simon | -Original Message- | From: David Feuer [mailto:[EMAIL PROTECTED]] | Sent: 20 February 2002 08:43 | To: [EMAIL PROTECTED] | Subject: Haskell 98 Report | | | Is the revised Haskell98 report going to be put in its proper | place on the web site any time soon? As it is, it is sitting | off to the side while the old Report sits in the seat of honor. | | David Feuer | ___ | Haskell mailing list | [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell | ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
RE: foralls in class assertions
OK, so it does look as though it's the same idea as that described in our paper. Good. I have not implemented, yet. As always my implementation priorities are strongly influenced by my perception of whether some enhancement would be used. Maybe you can outline why such a change would be useful to you? I only have the example in our paper as motivation so far. Simon | -Original Message- | From: Ashley Yakeley [mailto:[EMAIL PROTECTED]] | Sent: 20 February 2002 01:08 | To: Simon Peyton-Jones; Haskell List | Subject: RE: foralls in class assertions | | | At 2002-02-19 09:21, Simon Peyton-Jones wrote: | | I don't know if it makes sense. You've written down some syntax, | but it's not clear to me what you intend by it. | | Hmm... it should be straightforward... | | instance (forall a. Eq a = Eq (f a)) = Eq (Rose f a) where.. | | I assume that the 'a' quantified in (forall a. ...) is not | the same as | the 'a' in 'Rose f a'? | | | instance | | ( | | forall a. HasIdentity (m a a), | | forall a b c. Composable (m b c) (m a b) (m a c) | | ) = | | Category m; | | This means 'if for all a, HasIdentity (m a a), and also for | all a b c, | Composable (m b c) (m a b) (m a c), then Category m'. | | (forall a. HasIdentity (m a a)) as a class assertion declares a | property of m. It says that for all types a, there's an instance | HasIdentity (m a a). | | | Or even allow the foralls their own context: | | | | foo :: (forall a. (C a b) = D a c) = T b c; | | This means foo has type (T b c), where for every type a for | which there's | an instance C a b, there's an instance D a c. | | | class | | ( | | forall a. HasIdentity (m a a), | | forall a b c. Composable (m b c) (m a b) (m a c) | | ) = | | Category m; | | Personally I think the 'superclass' arrow in class | declarations should | point the other way, as in '='. After all, instances of the | class imply | instances of the superclasses, not the other way around. | | But that aside, this means 'Category is a class on m, | provided that for | all types a, there's an instance HasIdentity (m a a), and | also for all | types a b c, there's an instance Composable (m b c) (m a b) | (m a c)'. | | | -- | Ashley Yakeley, Seattle WA | | ___ | Haskell mailing list | [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell | ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: forcing IO operations
liftIOtoMyMonad_ :: IO () - MyMonad () liftIOtoMyMonad_ m = liftIOtoMyMonad' (const m) () I'm having problems compiling this one: The last statement in a 'do' construct must be an expression ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: forcing IO operations
[answering myself...] liftIOtoMyMonad_ :: IO () - MyMonad () liftIOtoMyMonad_ m = liftIOtoMyMonad' (const m) () I'm having problems compiling this one: The last statement in a 'do' construct must be an expression The problem is not related with liftIOtoMyMonad_ , but with liftIOtoMyMonad and liftIOtoMyMonad'. I think its an identation problem. Re-writing these funcions as follows solves the problem: liftIOtoMyMonad' :: (a - IO ()) - a - MyMonad () liftIOtoMyMonad' p q = StateMonad $ \s - (do p q return ((),s)) liftIOtoMyMonad :: IO a - MyMonad a liftIOtoMyMonad p= StateMonad $ \s - (do y - p return (y,s)) At least by now, all the ideas are working very well... great help Jay, thanks a lot! -- Andre ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: forcing IO operations
On Thu, 21 Feb 2002, Andre W B Furtado wrote: liftIOtoMyMonad_ :: IO () - MyMonad () liftIOtoMyMonad_ m = liftIOtoMyMonad' (const m) () I'm having problems compiling this one: The last statement in a 'do' construct must be an expression No problems here using no flags either. ghc-5.00 Hmmm... hugs Feb2001 seems to complain about my source (different reason). Which version of which compiler? (Btw, upon further review I cant think of a good reason for that function to exist. liftIOtoMyMonad can do anything liftIOtoMyMonad_ can handle. Essentially liftIOtoMyMonad_ = liftIOtoMyMonad but with a much more restrictive type) Jay Cox ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Monadic Call/CC?
Has anyone investigated monadic call-with-current-continuation in
Haskell? Given this:
class (Monad m) = PeirceMonad m where
{
peirceM :: ((a - m b) - m a) - m a;
};
...which Monads can be made PeirceMonads?
The corresponding non-monadic function:
peirce :: ((a - b) - a) - a;
probably can't be defined.
--
Ashley Yakeley, Seattle WA
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Re: a universal printer for Haskell?
My point is that there are some things that can't easily be expressed in current Haskell (like generic printing) that are useful and might be aided by meta-programming technology. The interesting question is can it be done in a way that preserves whatever we want from the type system: safety, security, efficiency, error detection ... You don't need meta-programming technology (reflection) to do things like generic prinitng. A generic programming extension of Haskell (like Generic Haskell, or derivable classes) can do the job for you. Have a look at: http://www.generic-haskell.org/ -- Johan ___ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: a universal printer for Haskell?
You don't need meta-programming technology (reflection) to do things like generic prinitng. A generic programming extension of Haskell (like Generic Haskell, or derivable classes) can do the job for you. Isn't generic programming usually based on a kind of compile-time reflection (if the argument is of this type, do this, else..)? And don't you write generic functions with the intention that the implementation will figure out the approriate type-specific variants, i.e., you write your code at a level of abstraction that is not easily reached with the standard language tools -- a meta level, where functions at different types are the first-class objects of discourse? I find it helpful to think of generic programming support as one way of integrating well-behaved subsets of reflection and other meta-programming techniques into Haskell. It is partly a trade-off: you get some of the features and avoid some of the problems of a fully reflective architecture. It is also a specialisation: by avoiding the full generality, the specific subset of features can be designed in a structured fashion, with the application domain in mind, making them easier to use for that domain. Claus (another fan of reflection and meta-programming, who would like to get their advantages without their disadvantages -- the latter are more clearly visible in a pure functional language than in Lisp) ___ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: a universal printer for Haskell?
You don't need meta-programming technology (reflection) to do things like generic prinitng. A generic programming extension of Haskell (like Generic Haskell, or derivable classes) can do the job for you. Isn't generic programming usually based on a kind of compile-time reflection (if the argument is of this type, do this, else..)? Yes, you might view it as compile-time reflection. Programs are still typable. And don't you write generic functions with the intention that the implementation will figure out the approriate type-specific variants, i.e., you write your code at a level of abstraction that is not easily reached with the standard language tools -- a meta level, where functions at different types are the first-class objects of discourse? If you view that as a metalevel I agree. However, it is the intention you never see the generated functions at different types: the compiler can (in priciple) completely hide those from the programmer. In that sense there is just one level: Generic haskell offers you normal Haskell functions and generic functions. I find it helpful to think of generic programming support as one way of integrating well-behaved subsets of reflection and other meta-programming techniques into Haskell. It is partly a trade-off: you get some of the features and avoid some of the problems of a fully reflective architecture. It is also a specialisation: by avoiding the full generality, the specific subset of features can be designed in a structured fashion, with the application domain in mind, making them easier to use for that domain. Agreed. -- Johan ___ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: Survival of generic-classes in ghc
| and I know from testing earlier versions that the
| generic-classes support was pretty buggy. Is there any hope
| of a revival? Does it already work in CVS? I suspect it will
| rot away if nobody works on it.
|
| Any comments from the implementors - does the idea fit well
| with ghc? Is it a lot of work to make it more stable?
No, it should not be a lot of work to revive, and I will do it.
Keep bugging me until I do.
One thing that is slowing me down is a design uncertainty: how to deal
cleanly with constructors. To write read, show, etc, one needs access
to
the constructor name, fixity etc. We dance around that a little in the
paper.
I'm thinking of this design:
-- An example data type
data List a = Nil | Cons a (List a)
-- The ring type derived from it
-- Note the Con wrapped around the constructors
data ListO a = Con NilT 1 :+: Con ConsT (a :*: List a)
-- Con is part of the Generics library, like 1, :*:, :+:
newtype Con c a = Con a
class ConCls c where
name :: c - String
arity :: c - Arity
..etc..
data NilT -- Phantom types
data ConsT -- one per constructor
instance ConCls NilT where
name _ = Nil
...etc...
instance ConCls ConsT wher
name _ = Cons
...etc...
Now you can write
class Show a where
show :: a - String
show {| Con c t |} (Con x) = (name (undefined::c)) ++ show x
...etc..
Note the undefined::c; it is really just a type argument to name, so
that we get the string for the right constructor. It's a bit clunky,
though.
Another possiblity would be to make the ConCls class look like this
class ConCls c where
name :: String
arity :: Int
...etc...
Now we'd have to give an explicit type argument at the call site:
show {| Constr c t |} (Con x) = (name {| c |}) ++ show x
I quite like the thought of being able to supply explicit type
arguments
but I don't konw how to speak about the order of type parameters.
What order does map takes its two type parameters in?
Another question is whether we need an indication that we have reached
a field of the constructor. Should we have:
data ListO a = Con NilT (Field 1) :+: Con ConsT (Field a :*: (Field List
a))
newtype Field a = Field a
Without this, it's hard to write a generic function to count the number
of
fields of the data type. But in general, one might want to know when
making the transition from this type to the argument types of the
constructors.
I think that the main reason I'm not making much progress is that I
don't
know what design choices to make. I'd be glad to discuss it with
interested
parties.
Simon
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Re: a universal printer for Haskell?
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 On Wednesday 20 February 2002 08:46, Bernard James POPE wrote: There are numerous ways to provide security for your data types. (In)Visibility isn't security. I have more than often witnessed Java users who thought private keyword was for security. I think it's obvious, with many years of worldwide experience of Internet security, why obscurity is *not* security. Thanks, - -- Eray Ozkural (exa) [EMAIL PROTECTED] Comp. Sci. Dept., Bilkent University, Ankara www: http://www.cs.bilkent.edu.tr/~erayo GPG public key fingerprint: 360C 852F 88B0 A745 F31B EA0F 7C07 AE16 874D 539C -BEGIN PGP SIGNATURE- Version: GnuPG v1.0.6 (GNU/Linux) Comment: For info see http://www.gnupg.org iD8DBQE8dCTGfAeuFodNU5wRAjGsAJ4tq8Nqg5Vh4pANHbMZ0JT+u1iVpgCcDY7i PI0TC9Y+DnVAV8AstF2ovmk= =+xqN -END PGP SIGNATURE- ___ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
Haskell problem
Hi, I'm trying out some combinatorial parsers, and I ran into a slightly inelegant construction. To parse a sequence of things, we have a function like pThen3 :: (a-b-c-d) - Parser a - Parser b - Parser c - Parser d pThen3 combine p1 p2 p3 toks = [(combine v1 v2 v3, toks3) | (v1, toks1) - p1 toks, (v2, toks2) - p2 toks1, (v3, toks3) - p3 toks2] The problem with this is that this structure has to be duplicated for pThen2, pThen4, and so on. These other forms are very similar to pThen3, but there seems to be no way to capture this in Haskell's type system, as the combine function has a different signature for each pThenX. (This is actually the first time the Haskell type system has got in my way rather than helping.) Is there a way around this problem? mrak ___ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
Haskell problem
Mark Wotton writes: | Hi, | | I'm trying out some combinatorial parsers, and I ran into a slightly | inelegant construction. To parse a sequence of things, we have a function | like | | pThen3 :: (a-b-c-d) - Parser a - Parser b - Parser c - Parser d | pThen3 combine p1 p2 p3 toks = | [(combine v1 v2 v3, toks3) | (v1, toks1) - p1 toks, | (v2, toks2) - p2 toks1, | (v3, toks3) - p3 toks2] | | The problem with this is that this structure has to be duplicated for | pThen2, pThen4, and so on. These other forms are very similar to pThen3, | but there seems to be no way to capture this in Haskell's type system, as | the combine function has a different signature for each pThenX. (This is | actually the first time the Haskell type system has got in my way rather | than helping.) Is there a way around this problem? If you can build the list of tokens into the state of your Parser monad - which would include making Parser a a distinct type instead of an alias for [Token] - [(a, Token)] - you could condense pThen3 down to this: pThen3 combine p1 p2 p3 toks = do v1 - p1 v2 - p2 v3 - p3 return (combine v1 v2 v3) which is equivalent to the liftM3 function from the Monad library. You'd still be stuck with a family of lifting functions, but at least they're predefined. I don't see any way of getting by with a fixed number of lifting functions, unless you're willing to clutter the call sites: infixl 0 `ap` ap :: Parser (a - b) - Parser a - Parser b ap = Monad.ap ... ... Monad.liftM f p1 `ap` p2 `ap` p3 `ap` p4 Regards, Tom ___ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Survival of generic-classes in ghc
On Wed, Feb 20, 2002 at 01:15:36PM -0800, Simon Peyton-Jones wrote:
Another possiblity would be to make the ConCls class look like this
class ConCls c where
name :: String
arity :: Int
...etc...
Now we'd have to give an explicit type argument at the call site:
show {| Constr c t |} (Con x) = (name {| c |}) ++ show x
I quite like the thought of being able to supply explicit type
arguments
but I don't konw how to speak about the order of type parameters.
What order does map takes its two type parameters in?
Sorry, this seems like a non-sequitur to me?
'map' has type '(a-b) - [a] - [b]'; supplying explicit type
parameters would mean giving values to 'a' and 'b'. If I wanted to
propose notation for this, I would suggest, e.g.,
(map :: (String - Int) - [String] - [Int]) length [Hello, World]
'name' (above) has type 'String'; the '{| c |}' is not providing a type
parameter in the same sense.
What am I missing?
Best,
Dylan
msg01379/pgp0.pgp
Description: PGP signature
