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: [Ha
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:
>
> in
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, 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
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),
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
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,
It depends what sort of polymorphism you want theta to have.
If your function types involve concrete types you could write something
like
type IntMap = Int -> Bool -> String
and then say
theta :: IntMap -> Int -> String
If you want the argument function to be completely polymorphic you can say
t
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 th
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
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 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, I forgot the main question I was raising.
Even if we need something other than mdo, do we need to make a distinction
between do and mdo? If left tightening is satisfied then do and mdo are
equivalent for nonrecursive blocks. If we are willing to give up shadowing
a compiler could translate
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 stan
x27;s thesis.
> On Wed, Sep 17, 2003 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?
>
> Th
> hello,
> i have no strong feelings about that either way,
> however since in haskell we do not have "let" vs "let rec" distinctions,
> perhaps we should not have "do" vs "do rec" distinction.
> this of course would break programs relying on shadowing
> (and at least i write quite a few of those
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 inf
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.
Hopefu
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)
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
-fallo
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 a
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. W
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 th
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, su
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) wher
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
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
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
doesn
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 h
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