Wish list: RULES, line number and filenames.
Dear ghc-team,
At the moment I think it is only possible that
error messages about functions can refer to line
numbers and names of source files at the points
of *definition* of these functions. These error
messages are the ones that ghc automatically
generates when there is a pattern matching error.
I think it would be useful to have error messages
about functions that refer to the line number and
the name of the source files at the moment these
functions are *used*. This would make it a lot
easier to locate errors.
I also think it would be handy to give the user
more control about line numbers and file names.
One possibility (modulo newlines in the RULES section)
would be an extension as follows:
{-# RULES
"lookupFM.range check" forall m key . rdMap m key =
maybe (lookupFmError #LINE #FILE)
id
(#lookupFM m key)
#-} --
lookupFmError line file
= error $ concat ["lookupFM :: key not in range in line ",line," in ",file]
The function #lookupFM would be the ``real''
lookupFM function. The idea is that after debugging
of a function one can just disable a rule in the
RULES section.
Just a thought.
Regards,
Marc van Dongen
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Re: Haskell and the NGWS Runtime
Why not Linux? Regards Chris Saunders [EMAIL PROTECTED] - Original Message - From: "Bill Halchin" [EMAIL PROTECTED] To: [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] Sent: Thursday, August 03, 2000 10:49 PM Subject: Re: Haskell and the NGWS Runtime To Linux? :^) From: "Chris Saunders" [EMAIL PROTECTED] To: [EMAIL PROTECTED], "Erik Meijer" [EMAIL PROTECTED] CC: "Marcin 'Qrczak' Kowalczyk" [EMAIL PROTECTED], [EMAIL PROTECTED] Subject: Re: Haskell and the NGWS Runtime Date: Thu, 3 Aug 2000 22:24:14 -0400 It seems to me that this .Net thingy is a runtime and therefore could potentially be as portable as anything from Java. This runtime just needs to be ported to other operating systems similarily to the Java runtime. Regards Chris Saunders [EMAIL PROTECTED] - Original Message - From: "Kevin Glynn" [EMAIL PROTECTED] To: "Erik Meijer" [EMAIL PROTECTED] Cc: "Marcin 'Qrczak' Kowalczyk" [EMAIL PROTECTED]; [EMAIL PROTECTED] Sent: Thursday, August 03, 2000 8:57 PM Subject: Re: Haskell and the NGWS Runtime I don't believe this says anything about support for other OS's. I think the devices here are hardware, (PCs, handhelds, phones, fridge interfaces, ...) Of course Microsoft believes that some day, very soon, all devices will run (a version of) Windows. Hence this statement refers to Microsoft's announced plans to port .NET to all Windows OS's, including WinCE. Do you have another reference which is more convincing? k Erik Meijer writes: Not "at least" but "only". I haven't heard of plans for .NET on any non-Windows platform. Then you should listen more closely! a quote from the .NET whitepaper: Microsoft .NET proactively adapts to what you want to do, on any of your devices. This inversion of the traditional installation-dependent application model is a necessity in a world where users will enjoy the benefits of services on multiple devices. http://www.microsoft.com/net/ Erik Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com
RE: Haskell and the NGWS Runtime
A few comments on this (stuff after the line beneath): The C implementation isn't really that inefficient. A factor of log(n) in average of course a factor of n i worst case. This doesn't change when using a lazy language! because of the nature of quicksort. As a matter of fact you have to have a "nice" version of merge sort (there are several variants - see fx Ralf Hinze, A Data-structural Look at Sorting, 1998, I don't know if it has been published except on this list) to be sure that (hd (sort list)) runs in time O(n). But, you are right a degree in CS doesn't guarantee that you know about complexity, but neither does programming in a lazy language. Personally I'm programming large systems in Prolog (www.pdc.dk) upto 150K lines. We try to make programs readable and correct firstmost, when they are too slow we measure where and fix it. Carsten Kehler Holst Fergus wrote: I guess one could argue that the costs of most other things pale in comparison to the costs of having lazy evaluation as the default ;-) Of course, if you're the sort of person who likes to write "head (sort lst)" to get the least member of a list, then lazy evaluation is incredibly efficient. Getting used to lazy evaluation, and really learning how to use it properly, is probably really the hardest thing about Haskell for someone who has already learned how to program using strict languages. Possibly even harder than monads. Funny/sad anecdote: I once saw a senior software engineer with over 15 years of C experience and a master's degree in CS, write the following code in C to locate the least member of an array: qsort(array, sizeof(array) / sizeof(array[0]), sizeof(array[0]), comparator); least = array[0]; Essentially, this is just "head (sort lst)" in C, which, as I daresay we all know, is NOT a lazy language! I actually had to explain to her why it was inefficient. Depending how you look at it, this is either strong evidence that lazy evaluation is a more natural way to think than strict evaluation, or proof that a master's in CS doesn't necessarily mean you really know anything about programming. Craig
Re: Haskell and the NGWS Runtime
We're drifting a bit off Haskell here, but...
At 10:57 am +1000 4/8/00, Kevin Glynn wrote:
I don't believe this says anything about support for other OS's. I
think the devices here are hardware, (PCs, handhelds, phones, fridge
interfaces, ...) Of course Microsoft believes that some day, very
soon, all devices will run (a version of) Windows. Hence this
statement refers to Microsoft's announced plans to port .NET to all
Windows OS's, including WinCE.
Do you have another reference which is more convincing?
I haven't seen a WinCE version but at a recent conference one of the
exhibitors was offering a .NET on WindowsCE course - however when I
inquired they just said "ask MS, we don't know, we just teach the
courses" (somehow I don't think I'll be recommending them!) So that's
not too convincing!
They are talking phones - but that has to be a stripped down version.
However I'm not sure why I want Haskell on my phone ("the phone with
higher-order polymorphic lazy dialing"?)
As to others OSES...
At 10:24 pm -0400 3/8/00, Chris Saunders wrote:
It seems to me that this .Net thingy is a runtime
and therefore could potentially be as portable
as anything from Java. This runtime just needs
to be ported to other operating systems similarily
to the Java runtime.
Porting JVM is a big enough job (you find a lot of "native"
methods...) .NET has more paraphernalia than the JVM so it will be
quite a job. However I think MS is moving to "standardise" the IL
(the byte codes) which I guess is to suggest it is not a moving
target (not the the JVM really is but I hear the lack of JVM 2's has
been blamed on lack of info out of Sun - but that might be just
passing the blame)
At 5:59 pm +0200 3/8/00, Juan J. Quintela wrote:
nigel Disclaimer, as Fergus added one: I am working with Microsoft on .NET
nigel implementation, but I run Windows 2000 on my G3 PowerBook and take it
nigel to Microsoft with me. I'm biased on everything :-)
Windows 2000 in a G3 Powerbook? I am lost here :((
Why have any other computer when you can have a Mac?
Mine runs:
DVD Movies
MacOS
JVM
Playstation games
Windows 95
Windows 2000 (a bit slugglish)
and could run:
Linux (but I have no use for it at present)
At 2:07 am +1000 4/8/00, Fergus Henderson wrote:
Note that on x86 there are only six general purpose registers,
so you very quickly run out...
Who uses the x86? Oh I remember... ;-)
Cheers,
Nigel
--
--
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IIST Tel: +64 6 350 5799 2477
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New Zealand
It makes as much sense to wear a "cycle" style helmet in a car as on a bike...
Choosing to wear one on a bike but not in a car is mere inconsistency.
Refusing to wear one in a car while insisting others do so on a bike
is pure hypocrisy.
Will the new Labour government repeal the National government's hypocrisy,
or will they insult cyclists' like their predecessors?
Politics and hypocrisy before safety - the NZ Helmet Law, NZ's Shame
Re: Haskell and the NGWS Runtime
Why have any other computer when you can have a Mac? Mine runs: DVD Movies MacOS JVM Playstation games Windows 95 Windows 2000 (a bit slugglish) and could run: Linux (but I have no use for it at present) I notice that your Mac can run a lot of things, but among the things you actually run there is only one operating system (Win 2k). :) But I agree, Macs are cool. -- Lennart
Tackling the Awkward Squad
Simon Peyton-Jones tell us of his latest paper: Tackling the Awkward Squad: monadic I/O, concurrency, exceptions, and foreign-language calls in Haskell. http://research.microsoft.com/~simonpj/papers/marktoberdorf.ps.gz This 40-page tutorial focuses on explaining the "bits round the edges" of Haskell programs, rather than the beautiful functional core we all know and love. it took me a long time to understand monadic programming, but now that I do it hurts to hear monadic I/O and concurrency described as "bits round the edges of Haskell programs" and part of the "awkward squad" and outside the "beautiful functional core we all know and love". given that Dr Peyton Jones co-wrote "Concurrent Haskell" and "Imperative Functional Programming", I'm wondering if those words reflect his true opinion or whether it is an ironic reference to sentiments he has heard from other people. and I'd like to hear what Marcin thinks, too: is the IO monad outside the beautiful core of Haskell? thank you in advance.
Re: Haskell and the NGWS Runtime
Why have any other computer when you can have a Mac? Mine runs: DVD Movies MacOS JVM Playstation games Windows 95 Windows 2000 (a bit slugglish) and could run: Linux (but I have no use for it at present) I notice that your Mac can run a lot of things, but among the things you actually run there is only one operating system (Win 2k). :) Weird, nobody mentioned neither NetBSD nor OpenBSD... CS people are weird. :-) Cheers, Edrx http://angg.twu.net/ -- Recycle your keystrokes - http://angg.twu.net/eev-manifesto.html
Re: Haskell and the NGWS Runtime
Eduardo Nahum Ochs wrote: Why have any other computer when you can have a Mac? Mine runs: DVD Movies MacOS JVM Playstation games Windows 95 Windows 2000 (a bit slugglish) and could run: Linux (but I have no use for it at present) I notice that your Mac can run a lot of things, but among the things you actually run there is only one operating system (Win 2k). :) Weird, nobody mentioned neither NetBSD nor OpenBSD... CS people are weird. :-) I consider myself a CS person and I run NetBSD on all my machines. And I'm also weird. -- -- Lennart
RE: Haskell and the NGWS Runtime
Weird, nobody mentioned neither NetBSD nor OpenBSD... CS people are weird. :-) I consider myself a CS person and I run NetBSD on all my machines. And I'm also weird. I'm weird, but not a true 'CS' person. I run Linux -- do I need to move to NetBSD? -Brent
