On Thu, May 20, 2004 at 11:06:44PM +0100, MR K P SCHUPKE wrote:
I agree, I have made it not terminate myself with undecidable-instances,
Congratulations. ;-)
I also think prolog style backtacking would be a good idea... I think I said
that you either want full backtracking or you want to
On Fri, May 21, 2004 at 11:04:53AM +0100, Simon Peyton-Jones wrote:
Nothing difficult in principle, but the constraint solver is one of
the more delicate parts of GHC because GHC's constraint language has
become so complex.
Well, as my day job is working for a constraints lab, I feel it's my
On Thu, May 20, 2004 at 08:52:45AM +0100, Simon Peyton-Jones wrote:
| You don't say what you are trying to achieve. However it looks as if
| you mean If you want PO T, for some type T, first try (Bounded T, Enum
| T, SemiRing T) and if that fails try CSemiRing T. Or maybe the other
| way round.
On Thu, May 20, 2004 at 03:52:49PM +0100, MR K P SCHUPKE wrote:
I don't know whether this was apparent, but only the instance
pattern is used in determining which instance to use, so
PO a is the same as PO a ... you need to make them different
otherwise they don;t just overlap they are
On Thu, May 20, 2004 at 05:16:45PM +0100, MR K P SCHUPKE wrote:
That's not the notion of priority I was referring to.
Any type of priority would not help. As I said then the instance heads
are identical (PO a) and (PO a) - no kind of priority will help
differenciate the,
I wasn't talking
On Thu, May 20, 2004 at 05:27:43PM +0100, MR K P SCHUPKE wrote:
I wasn't talking about _any_ notion of ordering of instance heads; I
said that prioritising instance _declarations_ themselves, explicitly,
by 'name' would suffice.
How does that help... if you name the instances differently
On Thu, May 20, 2004 at 05:58:53PM +0100, MR K P SCHUPKE wrote:
The alternative to the current situation is to take into account the
dependancies of instances when selecting. The problem here is that
the compiler may select an instance, evaluate its dependencies, only
to discover somewhere
On Thu, May 20, 2004 at 07:34:18PM +0100, MR K P SCHUPKE wrote:
that is not the case with -fallow-undecidable-instances ... as far as
I understand it , ghc never considers the dependancies when selecting an
instance. If you don't think so you will need to show me an example where
it clearly
On Thu, May 20, 2004 at 09:25:20PM +0100, MR K P SCHUPKE wrote:
Thats it... Neither GHC nor Hugs pay any attention to the
dependancies when choosing which instance to use. The
dependancies are only considered after the decision has
been irrevocably made. If the dependancies don't hold, the
The following rings a faint bell from somewhere, but if there's a standard
workaround I can't recall or lay my hand on it currently:
class PO a where
(|=) :: a - a - Bool
class Num a = SemiRing a
class SemiRing a = CSemiRing a
instance (Bounded a, Enum a, SemiRing a) = PO a where
On Mon, Feb 17, 2003 at 11:00:13AM -, Simon Marlow wrote:
I have some CGI programs running with Hugs and I want to use GHC
instead.
What changes must I do to the .hs file?
Is it an easy job?
Depends on lots of things really.
The CGI library that comes with GHC is
Alex
As Simon M says, if you (or anyone else) felt able to write up a
standalone summary
of what the problem is, and what the solution is, I'd love to add it to
the GHC
FAQ or documentation somewhere. In my experience, simply explaining the
problem
clearly is quite tricky. (E.g. the
Thanks to all for the replies; Hal's resolution rings a bell, now that
I think about it, from Ye Olde Days when cygwin was a ghc pre-req -- just
didn't think of it when installing more recently on a new machine. (Install
in haste, repent at leisure.) Claus' suggestion about relative paths
does
Using ghc-5.04.2 under cygwin, and cygwin (v. 1.3.10-1), I'm having some
horrible problems with inconistent treatment of filenames, especially
when using (gnu, cygwin) make. In a nutshell, make seems to be passing
paths such as /usr/local/hmake (etc) to ghc, which is, as I understand
it,
Just write the list twice, once with the quotes and commas and once
without? Alternative I guess you could try to transform one into the
other using sed, perl, python, etc. but I would just do it the easy way.
Doesn't everyone on this list use Haskell for their string-processing,
then? ;-)
Hi guys. Has anyone been so rash as to try this? Any indications
as to the likely "degree of difficulty"? I'd have a go myself, but
I'm rather busy with teaching. (Which is ironic, since teaching is
what I want it for...)
Cheers,
Alex.
___
Hi there. I fear this may end up being not so much a TclHaskell
as a 'power Tcl/Tk' question, but I thought I'd try here first on the
off-chance.
I'm looking for a widget that acts essentially like a listbox (scrolls,
selectable entries), but which isn't restricted to single lines of text
in
SPJ:
Yes, Jeff Lewis is well advanced with adding functional dependencies
to GHC. Certainly, if you get GHC from the CVS tree you are getting
wads of his F-D code. I don't think it's completed yet, though.
Stay tuned
Excellent stuff. I _think_ this solves a problem I may be about
to have
Keith Wansbrough:
If the Integer is greater than 2^64-1 then simply
pass NULL to select(): I think 595 000 years is near enough forever
given current operating systems...
Quincentomillennium bug, anyone?
;-)
Cheers,
Alex.
Although I'd read the restriction in advance, I nevertheless unwittingly
contrived to try and write a binding-group style pattern-match against
an existentially quantified data constructor. Oops. (Actually, I did
it twice, what's worse...) I can imagine this is indeed an irksome
thing to TC,
Me:
| Although I'd read the restriction in advance, I nevertheless
| unwittingly
| contrived to try and write a binding-group style pattern-match against
| an existentially quantified data constructor. Oops. (Actually, I did
| it twice, what's worse...) I can imagine this is indeed an
Keith Wansbrough:
I've just added a new RTS option to GHC in the CVS repository. Running
a program compiled with -prof with the -xc runtime option on will cause
it to display the current cost-centre stack on stderr whenever an
exception is raised. This will give you an idea of which
Hi all. Just started playing around with ccall, and while I managed
to get my toy program to Do The Right Thing, I got a mildly alarming
looking warning message from gcc, re: athe lack of an explicit type
for the generated C call. I don't see anything about this in the users
guide, either
Hi there.
it is mentioned in the user's guide,
http://haskell.org/ghc/docs/latest/users_guide/users_guide-5.html#glasgow-fo
reign-headers
Ah, that: I managed to read that entire section at least once, and
completely misunderstand. I thought that was talking about something
else
Hi Fergus.
data OrdFuncExist = OE (Ord a = Char - a)
That's not the syntax for a existential type,
that's the syntax for a universally quantified type
with rank-2 polymorphism. With that syntax, the
argument of `OE' must be a polymorphic function
with type `forall a . Ord a = Char -
Hi Mark, all: thanks for the swiftly muddle-dispelling response.
| Here's some of the threatened examples:
|
| data OrdFuncExist = OE (Ord a = Char - a)
| data OrdListExist = OLE (Ord a = [a])
Perhaps this is a GHC/Hugs difference, but the syntax that you've
used here isn't
After a release, the version number in the repository is bumped up by
one, that's all there's to these rumours. A release of 4.05 isn't due
anytime soon (you have to report *all* the bugs in 4.04 first :-)
I had better install it first, then...
Unless you want to become a fptools CVS
Does anyone else have experiences of building TclHaskell under CygWin?
I'm assured that it ought to be possible, but have had no luck; crib
sheets greatly appreciated.
(Partial credit for negative results like 'it's a bust, drop back
and punt to Linux'.)
Cheers,
Alex.
What's the state of the art as regards calling Haskell functions from
'the outside world'? I note that Haskell Direct has this in its
manifesto, but says "currently unsupported". Does that mean a moderate
size black hole at the centre of something still potentially usable,
or nothing much at
Quite impressed with 4.02 so far -- it walks the walks, see promohype
elsewhere, why should I give you all too much free advertising? ;-)
It does indeed seem to be more go-faster than 3.02, _but_:
No profiling! Boo, hiss.
Funny space behaviour -- a module I have that contains just one
Hi Simon, thanks for the tips;
We havn't checked out the profiler, remember.
I'm using 3.02, I should have mentioned. (For this very reason.)
Here's our convention for splitting up the interface file name space:
d...dictionary identifiers
(local
What do "$m" identifiers correspond to? I'm getting one of these lob
up in a -prof -auto cost centre, and I don't know what/where/how it
corresponds to.
While I'm on the general topic, any hints'n'tips on decoding $d's?
In a name like $dEqPriority0, I presume the first two elements
are Class
Ah-hah! So I should just be able to write, in rts.c:
#include "Rts.h"
void defaultsHook (void) {
RTSflags.GcFlags.stksSize = 102 / sizeof(W_);
RTSflags.GcFlags.heapSize = 802 / sizeof(W_);
}
Well, sort of. I forgot to mention that we
Looks like the docs are a tad out of date, sorry about that. Patch follows
(you want ghc/rts/RtsFlags.h and ghc/includes/Rts.h respectively).
Ah-hah! So I should just be able to write, in rts.c:
#include "Rts.h"
void defaultsHook (void) {
RTSflags.GcFlags.stksSize = 102
Well, so far I've gathered that syslibs ghc and posix have moved and been
renamed, and that the "full story" is hidden someplace within the docs
-- someplace I haven't yet been able to find.
Any further clues as to where I might find the dire fate that's befallen
hbc and contrib? Are these
Hi all. What's the current state of play with ghc (any version), on NT
machines?
Slainte,
Alex.
SPJ:
Same issue. Show [a] exists already and overlaps with Show [Blah].
3.0 is a bit more restrictive than 2.xx, but it is Righter I think.
Dissenting opinions welcome.
I think I semi-agree, though I think the change in ghc-3.00 ought to have
been more loudly flagged. (And not denied, as
While hacking around with MPCs, trying to define a variant of the
Collection class, mutated to suit my own fiendish ends, I ran into
this:
Intervals.hs:345:
Class type variable `e' does not appear in method signature
union2 :: s - s - s
What's the significance of this restriction?
Hi all.
To my horror, I've just discovered that ghc-2.04 appears to reverse the
recent trend of ghc releases by being significantly less efficient on
one of our Problem Child programs. In particular, it both takes (even)
more memory to compile; and the object code size is (even!) bigger.
The
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