On Wed, Aug 22, 2007 at 04:07:22AM +0100, Hugh Perkins wrote:
On 8/21/07, Andrew Coppin [EMAIL PROTECTED] wrote:
I highly doubt that automatic threading will happen any time this decade
- but I just learned something worth while from reading this email. ;-)
That's an interesting
On Wed, Aug 15, 2007 at 11:06:36AM -0700, Stefan O'Rear wrote:
On Wed, Aug 15, 2007 at 06:58:40PM +0100, Duncan Coutts wrote:
On Wed, 2007-08-15 at 10:50 -0700, Stefan O'Rear wrote:
OTOH, your proposal provides (IMO) much more natural syntax for
multi-pattern anonymous functions,
On Fri, Aug 10, 2007 at 03:54:23PM -0700, Greg Meredith wrote:
Haskellians,
A quick follow up. If you look at the code that i have written there is a
great deal of repeated structure. Each of these different kinds of sets and
atoms are isomorphic copies of each other. Because, however, of
On Thu, Aug 09, 2007 at 11:52:17AM -0700, David Roundy wrote:
On Thu, Aug 09, 2007 at 02:08:20PM +0100, Jules Bean wrote:
*snip*
A third example is with nested dos:
do x - bar y
baz
something $ do foo x
is not the same as
do baz
something $ do foo (- bar y)
much snipping
Also, note, if you use the operators in Control.Applicative, then:
return $ foo $(bar1) $(bar2) $(bar3) ...
can be:
return foo * bar1 * bar2 * bar3 ...
or:
foo $ bar1 * bar2 * bar3
I don't (personally) see how that's any more cryptic than placing brackets
On Thu, Jul 26, 2007 at 05:34:32PM -0400, anon wrote:
2007/7/26, Stefan O'Rear [EMAIL PROTECTED]:
As for why, it's just a matter of Haskell Committee taste. Nothing
too deep, just an arbitrary set of rules.
That's not much of an explanation, is it? I imagine someone must have
given the
On Fri, Jul 20, 2007 at 10:10:58PM +0200, Hugh Perkins wrote:
Newbie question: why does the following give Not in scope 'c' for the last
line?
I assume you meant
string :: Parsec.Parser String
string = do c - Parsec.letter
do cs - string
return c:cs
On Sat, Jul 07, 2007 at 06:49:25PM +0100, Andrew Coppin wrote:
Dave Bayer wrote:
I was beginning to accept that I might die before clearing my pipeline
of research projects I want to code up.
...so it's *not* just me!
Haskell has given me new hope.
Indeed. ;-)
Today I hve
On Fri, Jul 06, 2007 at 06:11:42PM -0400, Scott West wrote:
I conquered the below problem, but now I have another question:
How can one have two interface-classes that reference each other? For
example,
type Inter1 = Record (
MkFoo :=: Inter2 - IO ()
:*: HNil )
type Inter2 = Record
On Mon, Jun 25, 2007 at 08:53:18AM -0700, Dave Bayer wrote:
It continues to appear to me that ghc -Wall -Werror doesn't support
small Int constants without a per-use penalty, measured in code length.
Why not use ghc -Wall -Werror -fno-warn-defaulting, maybe with
default(Int)? It removes the
On Thu, Jun 21, 2007 at 04:37:20PM +0200, Tom Schrijvers wrote:
That wouldn't make a difference. If, from the pure Haskell point of view
we can't tell the difference between two expressions that denote the same
function, then operations in the IO monad should not be able to do so
either.
On Wed, Jun 06, 2007 at 02:50:12AM +0100, PR Stanley wrote:
PR Stanley wrote:
What do the ??? symbols represent?
I see you are still stuck in ISO-8859-1 and
deprived of international characters and
symbols. (And this reply in ISO-8859-1 too
accordingly; normally I use UTF-8.) Unicode
On Thu, May 31, 2007 at 10:42:57AM -0700, Greg Meredith wrote:
All,
All this talk about Mathematica and a reference to monadic treatments of
backtracking reminded me that a year ago i was involved in work on a
Mathematica-like widget. At the time i noticed that a good deal of the
structure
On Thu, May 31, 2007 at 10:03:05AM +0100, PR Stanley wrote:
What is the basic philosophy for Bool being a member of Ord?
I hear two questions, why is Bool a member of Ord at all, and
why was it ordered with False before True.
If I'm reading the reports correctly, the Ord instance was
On Fri, May 18, 2007 at 02:39:48AM -0400, Alex Jacobson wrote:
I am playing with using SYB to make generic indexed collections. The
current code is this:
data Syb = Syb [Dynamic] -- list of [Map val (Set a)]
empty item = Syb $ gmapQ (toDyn . emp item) item
where
On Tue, May 08, 2007 at 10:06:32AM +0100, Joel Reymont wrote:
I'm looking for suggestions on how to create invariants for the
following AST transformation code. Any suggestions are appreciated!
I asked this question before and Lennart suggested abstract
interpretation as a solution. This
On Tue, May 08, 2007 at 07:39:15AM +0100, Joel Reymont wrote:
If you happen to be formatting C I've also worked out how to get
nice argument
lists out of both pretty printers.
I'm formatting C# but I'll certainly take your arg list tips.
These narrow like
foo (a, b)
foo (a,
b)
foo
On Mon, May 07, 2007 at 10:38:19PM +0100, Joel Reymont wrote:
Folks,
Are you using UU.PPrint [1]? Can you tell me how to print stuff like
this?
{
blah
blah
}
I tried the following which sort of works but doesn't return the
closing brace to the indentation level of the
On Thu, May 03, 2007 at 04:59:58PM -0700, John Meacham wrote:
I believe it is because a stack cannot be garbage collected, and must be
traversed as roots for every garbage collection. I don't think there are
any issues with a huge stack per se, but it does not play nice with
garbage collection
Sending to the right list this time, with some additions.
Just to show what kind of problems we are currently facing. The
following type checks in our EHC compiler and in Hugs, but not in the
GHC:
module Test where
data T s = forall x. T (s - (x - s) - (x, s, Int))
run :: (forall
On Tue, Apr 17, 2007 at 12:50:48PM +0200, Doaitse Swierstra wrote:
Just to show what kind of problems we are currently facing. The
following type checks in our EHC compiler and in Hugs, but not in the
GHC:
module Test where
data T s = forall x. T (s - (x - s) - (x, s, Int))
run ::
On Tue, Apr 17, 2007 at 11:39:03PM -0700, Brandon Michael Moore wrote:
On Tue, Apr 17, 2007 at 12:50:48PM +0200, Doaitse Swierstra wrote:
Just to show what kind of problems we are currently facing. The
following type checks in our EHC compiler and in Hugs, but not in the
GHC
On Thu, Apr 19, 2007 at 02:47:30AM +0100, Neil Mitchell wrote:
Hi,
I've been wondering what is essential to Haskell and what isn't. Not
from a point of view of what could be removed from the language, but
what could be removed from a Core language.
Given the features of higher-order,
On Wed, Apr 11, 2007 at 02:21:41PM +0100, Will Newton wrote:
On 4/11/07, kynn [EMAIL PROTECTED] wrote:
Perl is a large, ugly, messy language filled with quirks and
eccentricities,
while Haskell is an extremely elegant language whose design is guided by a
few overriding ideas. (Or so I'm
On Tue, Apr 10, 2007 at 11:03:32AM -0700, Oren Ben-Kiki wrote:
On Tue, 2007-04-10 at 12:14 +0200, apfelmus wrote:
Oren Ben-Kiki wrote:
The code is in http://hpaste.org/1314#a1 if anyone at all is willing
to take pity on me and explain what I'm doing wrong.
There is an important point to
On Wed, Apr 11, 2007 at 12:13:10AM +0200, Bas van Dijk wrote:
Hello,
For my own exercise I'm writing a function 'weave' that weaves a
list of lists together. For example:
weave [[1,1,1], [2,2,2], [3,3]] == [1,2,3,1,2,3,1,2]
weave [[1,1,1], [2,2], [3,3,3]] == [1,2,3,1,2,3,1]
Note that
It looks like all you can do with DirStream is get the filename, not
look at any other fields of the dirent - actually, it seems name
is the only standard field. You might as well use
getDirectoryContents, unless you have a directory so huge that
a list of all the filenames takes too much memory!
On Wed, Mar 14, 2007 at 06:05:31PM -0700, David Brown wrote:
Greg Fitzgerald wrote:
What we need is a library for a readonly filesystem. That is, all
the same functions but pure. I believe you could make this readonly
library by wrapping each readonly I/O function with
On Mon, Mar 12, 2007 at 05:14:57PM -0500, John Goerzen wrote:
On 2007-03-06, Simon Marlow [EMAIL PROTECTED] wrote:
John Goerzen wrote:
possible to create a pipe going directly from program A to program B.
You certainly can pipe directly from one process to another:
That only works for
On Wed, Feb 14, 2007 at 10:04:32AM +, Simon Marlow wrote:
Perhaps I'm missing something, but doesn't GHC already detect the kind of
deadlock you're talking about here? When a thread is blocked and cannot be
woken up, it is sent the BlockedOnDeadMVar exception. It's more precise
than
Keith is talking about a comitted choice style of nondeterminism, where
one of the arguments is picked and the computation continues from there.
If you want a computation with backtracking, or a list of all possibly
results then you should use the list monad, or another monad that supports
On Fri, 2 Apr 2004, Simon Peyton-Jones wrote:
Your word is my command. 'Tis done.
Simon
| -Original Message-
| From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
On Behalf Of Wolfgang
| Jeltsch
| Sent: 21 March 2004 17:55
| To: The Haskell Mailing List
| Subject: [Haskell]
On Thu, 11 Mar 2004 [EMAIL PROTECTED] wrote:
Thanks! Oleg.
This works and it looks nice!
And now, my code can be like:
class FwdSig d where
(forall a. Sig a = a - w) - d - w
All the types that supports such forwarding are instances of FwdSig.
My Def type is:
instance FwdSig Def
I think the generics approach really is overkill here, but it's nice to
know the generics library.
For option processing Tomasz Ziolonka described a nice technique
in the post I refered to. You can find the post in the archives at
http://www.haskell.org//pipermail/haskell/2004-January/013412.html
On Fri, 5 Mar 2004, Vadim Zaliva wrote:
Hi!
I am new to Haskell, but I have background in various programming
languages (including Lisp)
I have very basic question, if there is a way to match algebraic types
constructors besides
use of pattern matching. I wrote today code like this:
On Fri, 27 Feb 2004, Simon Peyton-Jones wrote:
The idea that I've been throwing around is to be able to define a
separate namespace for each type; a function can either belong in a
global (default) namespace, or belong in a particular type's
namespace. So, in the above example, instead
On Fri, 27 Feb 2004 [EMAIL PROTECTED] wrote:
On 27/02/2004, at 1:13 PM, [EMAIL PROTECTED] wrote:
1) now I have to manually declare a class definition for every single
function, and I have to declare it in advance before any module defines
that function (most serious problem; see below),
2)
On Thu, 11 Dec 2003, Robert Will wrote:
Hello,
As you will have noticed, I'm designing a little library of Abstract Data
Structuresm here is a small excerpt to get an idea:
class Collection coll a where
...
(+) :: coll a - coll a - coll a
reduce :: (a - b) - b
Control.Monad.Reader defines instances of Monad and MonadReader for
((-) r). Strangely enough, the documentation claims the Monad instance
comes from Control.Monad, which is untrue.
Here's the relevant chunk of the file. It looks like you came up with
exactly the same code (modulo names).
--
On Wed, 26 Nov 2003, Ken Shan wrote:
Hello,
Consider the following code, which uses type classes with functional
dependencies:
{-# OPTIONS -fglasgow-exts #-}
module Foo where
class R a b | a - b where r :: a - b
-- 1
rr :: (R a b1, R a b2) = a - (b1, b2)
rr a
On Mon, 10 Nov 2003, Simon Peyton-Jones wrote:
| Also, I tried to update and rebuild, but the makefiles seem to have
the
| dependencies wrong or something. I compiles THSyntax.hs by hand, then
ran
| into some trouble with files that needed some modules from GHCI trying
| (and dying) to
Hi everyone
I've built GHC from CVS and I'm getting some odd errors about overlapping
instances. This is different from 6.0.1, but it's not obvious it is wrong,
so I'm probably missing something here.
The example is
class A x
class (A x) = B x
instance A x
instance B x
The new GHC complains
On Fri, 7 Nov 2003, Marta Isabel Oliveira wrote:
Ok, i read the page but i'm still stuck.
I'm reading some papers about cata, ana and hylomorphisms but i need to know where
to start putting it to code.
So,
1. in order to have a pre-processor, i need to have a module with ALL data
On Wed, 5 Nov 2003, Simon Peyton-Jones wrote:
| More overlapping:
| Allow any overlapping rules, and apply the most specific rule that
| matches our target. Only complain if there is a pair of matching
| rules neither of which is more specific than the other.
| This follow the spirit of
On Tue, 4 Nov 2003, Simon Peyton-Jones wrote:
| We really should change GHC rather than keep trying to work around
stuff
| like this. GHC will be my light reading for winter break.
Maybe so. For the benefit of those of us who have not followed the
details of your work, could you
Thanks for the clever code Oleg. I've tried to extend it again to track
the types of methods as well as just the names, giving a functional
dependancy from the class, method, and to result type. I can't get the
overlapping instances to work out, so I'm handing it back to a master,
and the rest of
I'm pretty sure this is sequence.
Brandon
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Haskell-Cafe mailing list
[EMAIL PROTECTED]
http://www.haskell.org/mailman/listinfo/haskell-cafe
On Mon, 13 Oct 2003, Graham Klyne wrote:
I've run across a minor coding niggle on a couple opf accosions when using
a type constructor with field selectors. The full code of my test case is
below. The value 'test2' evaluates to True.
The function that niggles me is this:
[[
On Wed, 8 Oct 2003 [EMAIL PROTECTED] wrote:
Hi, all.
I'm a newbie to Haskell so please bear with me if my questions sound silly.
In coding Haskell, I feel very inconvenient that the name of data
constructors for different types have to be different.
Also, when declaring named fields of a
On Fri, 26 Sep 2003 [EMAIL PROTECTED] wrote:
Brandon Michael Moore wrote regarding the first solution: chain of
super-classes:
I'm worried about large class hierarchies. If it works on the
java.* classes I should be fine. Have you used this approach before? I'm
worried about compile time
On Thu, 25 Sep 2003 [EMAIL PROTECTED] wrote:
Brandon Michael Moore wrote:
So I defined a class to model the inheritance relationships
class SubType super sub | sub - super where
upCast :: sub - super
Now I can define a default instance of HasFooMethod:
instance (HasFooMethod super
Note I've replied to haskell-cafe. This post is a bit chatty and low on
solid answers.
On Thu, 25 Sep 2003, Sean L. Palmer wrote:
A... should be split into A.. and .
I found a compromise: let's make it a lexing error! :-)
At least that agrees with what some Haskell compilers implement. No
I'm trying to build a nicer interface over the one generated by
jvm-bridge. I'm using fancy type classes to remove the need to mangle
method names. I would like methods to be automatcially inherited,
following an inheritance hierarcy defined with another set of type
classes.
My basic classes look
On Thu, 25 Sep 2003 [EMAIL PROTECTED] wrote:
On 25/09/2003, at 7:22 AM, Brandon Michael Moore wrote:
I'm trying to build a nicer interface over the one generated by
jvm-bridge. I'm using fancy type classes to remove the need to mangle
method names. I would like methods to be automatcially
On Sun, 21 Sep 2003, Dominic Steinitz wrote:
Brandon,
I get the error below without the type signature. My confusion was thinking
I needed rank-2 types. In fact I only need polymorphic recursion. Ross
Paterson's suggestion fixes the problem. I stole Even and Odd from Chris
Okasaki's paper
On Sat, 20 Sep 2003, Ross Paterson wrote:
On Sat, Sep 20, 2003 at 12:01:32PM +0100, Dominic Steinitz wrote:
Can anyone tell me why the following doesn't work (and what I have to do to
fix it)? I thought by specifying the type of coalw as rank-2 would allow it
to be used both at a and
Sorry about the empty message. Send /= Cancel
Can anyone tell me why the following doesn't work (and what I have to do to
fix it)? I thought by specifying the type of coalw as rank-2 would allow it
to be used both at a and (a,b).
Frank explained why the type you gave wouldn't work. I would
On Thu, 18 Sep 2003, Juanma Barranquero wrote:
Extremely-newbie questions:
Is there any way to know if a list is finite or infinite, other than
doing:
length l
and waiting forever? :)
I ask because I was learning Haskell by writing some pretty naive
implementation of surreal numbers,
at 11:41:24AM -0700, Brandon Michael Moore wrote:
In any case, I don't see the need for explicit rec groups. Can't GHC just
find the strongly connected components like it already does with let
bindings?
That's what GHC and Hugs do now for mdo (actually segments rather than
components
On Thu, 18 Sep 2003 [EMAIL PROTECTED] wrote:
Although a number of comments in this discussion make some sense,
I personally am getting worried about the direction that it is taking.
I have been a (fairly quiet) Haskell user for some time. I like it
because of the strong connection to
On Mon, 15 Sep 2003, Yu Di wrote:
data MyArrow a b = MyArrow ((String, a) - (String,
b))
i.e. there is an information asscioated with each
piece of data (represented by the string), and I want
to pass it around. And often the arrow's processing
logic will depend on the input information,
On Thu, 11 Sep 2003, Simon Peyton-Jones wrote:
OK, I yield!
The HEAD now runs this program. It turned out to be a case of
interchanging two lines of code, which is the kind of fix I like.
Simon
Cool! Yet another domain where haskell handles infinities quite happily.
Thanks.
Hopefully
On Sun, 14 Sep 2003, Glynn Clements wrote:
Brandon Michael Moore wrote:
Hal was pretty terse, so I'll explain why switching to putStrLn will help.
stdout is line buffered.
At least by default (see hSetBuffering). That means output will only be
flushed to the screen once a newline
On Sun, 7 Sep 2003, Ashley Yakeley wrote:
In article [EMAIL PROTECTED],
Brandon Michael Moore [EMAIL PROTECTED] wrote:
Detecting circularity in a derivation is equivalent to accepting a regular
infinite derivation for instances. Would you have a use for irregular
derivations?
Could
Hello everyone
I think I'm close to useful results on the instance restrictions.
First there's an obvious extension to the Haskell98 rule. The H98 rule
says the instance head must be a type constructor applied to type
variables, and the context must mention only those type variables. This
gives
Hi everyone.
I've been looking at the restrictions on instances in the H98 standard
and thinking about alternatives. I would like to have a body of data type
and class/instance declarations so I can test how useful various
extensions would be. Please send or direct me to code that requires
On Wed, 10 Sep 2003, Ashley Yakeley wrote:
Brandon Michael Moore [EMAIL PROTECTED] wrote:
A simple irregular type is
Irr a = Con a (Irr (F a))
(as long as F uses a)
Would this be an irregular type, with F as ((-) val)?
data SymbolExpression sym val a = ClosedSymbolExpression
Hi Ashley
See the thread Type Class Problem. In his post on Aug 22 Simon
Peyton-Jones said that it shouldn't be hard to implement, and mentioned
that it would ruin the property that dictionaries can be evaluated by
call-by-value. I couldn't puzzle out enough of the type class system to
make the
On 28 Aug 2003, Carl Witty wrote:
On Thu, 2003-08-28 at 13:10, Brandon Michael Moore wrote:
Unfortunately I don't have a useful syntatic condition on instance
declarations that insures termination of typechecking. If types are
restriced to products, sums, and explicit recursion
On Fri, 22 Aug 2003, Simon Peyton-Jones wrote:
Brandon writes
| An application of Mu should be showable if the functor maps showable
types
| to showable types, so the most natural way to define the instance
seemed
| to be
|
| instance (Show a = Show (f a)) = Show (Mu f) where
| show
On Tue, 26 Aug 2003, Konrad Hinsen wrote:
My Haskell experiments have reached a size in which debugging tools would be
more than welcome, so I looked around, and was very disappointed. I tried
Hood, which is a pain to use (lots of editing of the code required), I looked
at Buddha but didn't
On Sun, 17 Aug 2003 [EMAIL PROTECTED] wrote:
I defined type recursion and naturals as
newtype Mu f = In {unIn :: f (Mu f)}
data N f = S f | Z
type Nat = Mu N
An application of Mu should be showable if the functor maps showable types
to showable types, so the most natural way to
Is it fine if the interface uses JNI? The jvm-bridge is an excellent tool
if you can use JNI, but I don't know of anything that compiles Haskell to
java bytecode. There was a post a few years ago about an experimental Java
backend for GHC, but I haven't heard anything since, and the -J switch
You don't really need to change the buffering mode. stdout is line
buffered by default, so you just need to make sure a newline is printed
after your message. putStrLn adds a newline after the string it prints, or
you could use \n in the string literal. Try this:
main = do
--lots of code goes
To try some of the examples from paper Recursion Schemes from Comonads,
I wanted to define instances of Show and Observable for types defined as
the fixed point of a functor.
I defined type recursion and naturals as
newtype Mu f = In {unIn :: f (Mu f)}
data N f = S f | Z
type Nat = Mu N
An
On Thu, 14 Aug 2003, Wolfgang Jeltsch wrote:
On Thursday, 2003-08-14, 17:05, CEST, Kevin S. Millikin wrote:
On Wednesday, August 13, 2003 11:20 PM, Tn X-10n
[SMTP:[EMAIL PROTECTED] wrote:
is it possible to convert IO Bool to Bool?
Sure. Which Bool do you want? True?
toTrue
On Tue, 5 Aug 2003, Thomas L. Bevan wrote:
-BEGIN PGP SIGNED MESSAGE-
Hash: SHA1
I don't see that the contibutors files are fundementally different.
- From what I understand, it should be possible to write a
generic function,
importCSV :: FilePath - IO [ (String,String) ]
I'm wondering if there are any libraries out there for creating parsers
that lazily build up their result. I know I could thread the remaining
input through a parser by hand, but it seems like someone should have
already done it.
I'd like to be able to turn a stream of XML into a lazy tree of
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