Hello John,
Tuesday, February 07, 2006, 4:23:36 AM, you wrote:
data Eq a = Set a = Set (List a)
that is a sort of extension i will be glad to see. in my Streams
library, it's a typical beast and i forced to move all these contexts
to the instances/functions definitions:
data
On 2/5/06, Jim Apple [EMAIL PROTECTED] wrote:
Have we considered Restricted Data Types?
http://www.cs.chalmers.se/~rjmh/Papers/restricted-datatypes.ps
Nice to see my old paper hasn't sunk without trace!
As Taral pointed out, though, Restricted Data Types have not been implemented,
and
Am Freitag, 3. Februar 2006 00:06 schrieb John Meacham:
On Thu, Feb 02, 2006 at 03:09:35PM +, Henrik Nilsson wrote:
Now, I'm not saying that FDs are that important, only that it seems
to me they are. I'd be happy to be convinced of the opposite.
But from the above, it at least seems
From: Ross Paterson [EMAIL PROTECTED]
John Hughes wrote:
I would urge that either we stick with the present design, or, if bang
patterns are added (which a lot speaks for), that the language be
simplified at the same time so that patterns are matched in the same way
everywhere, and
From: John Meacham [EMAIL PROTECTED]
Subject: Re: Restricted Data Types
however, what prevents the following from being _infered_
return Foo :: Moand m = m Foo
so, we think we can specialize it to
return Foo :: Set Foo
however, we no longer have the constraint that Foo must be in Eq!
Maybe
John Hughes wrote:
That means that the Monad class is not allowed to declare
return :: a - m a
because there's no guarantee that the type m a would be well-formed. The
type declared for return has to become
return :: wft (m a) = a - m a
I'm confused. It seems like the type (a - m a)
On Jan 31, 2006, at 1:50 PM, Wolfgang Jeltsch wrote:
Am Montag, 30. Januar 2006 19:33 schrieb Isaac Jones:
[...]
Have you looked at the Helium language / compiler? It's a
stripped-down version of Haskell for teaching. Maybe that's what
you're actually suggesting? I think this is a great
On Tue, Feb 07, 2006 at 10:04:35AM +0100, Georg Martius wrote:
From the users point of view, the implementation in GHC works quite
well and a lot people use it. It would be a pity if they are not
included in the new standard. What is the problem of specifying what
is implemented.
They work
On Feb 7, 2006, at 9:49 AM, Malcolm Wallace wrote:
Robert Dockins [EMAIL PROTECTED] writes:
i would argue against treating tuples as pure syntactic sugar for
nested pairs; since the nesting carries hierarchical information, i
would expect (x,y,z) used in place of (x,(y,z)) to cause an error.
| Have we considered Restricted Data Types?
|
| http://www.cs.chalmers.se/~rjmh/Papers/restricted-datatypes.ps
|
|
| Finally, I wrote my paper before fundeps came on the scene. Some of
the contortions I went through
| in my simulation of RDTs could be avoided with the help of fundeps.
A key
| data Eq a = Set a = Set (List a)
|
| that is a sort of extension i will be glad to see. in my Streams
| library, it's a typical beast and i forced to move all these contexts
| to the instances/functions definitions:
Another reasonable alternative is
data Set a = Eq a = Set (List a)
Hello Robert,
Tuesday, February 07, 2006, 6:42:41 PM, you wrote:
More disturbing is the complete inability to write general functions
over tuples.
RD As I understand it, you still have to write down the instance
RD declarations when using '-fgenerics'.
only one generic instance. it's very
On Feb 7, 2006, at 11:29 AM, Bulat Ziganshin wrote:Hello Robert,Tuesday, February 07, 2006, 6:42:41 PM, you wrote: More disturbing is the complete inability to write general functionsover tuples. RD As I understand it, you still have to write down the instance RD declarations when using
Simon PJ thinks that Haskell' should include scoped type variables, and I
tend to agree. But I'm unhappy with one aspect of the way they're
implemented in GHC. What I don't like is that given a signature like
x :: a - a
there's no way to tell, looking at it in isolation, whether a is free
Bulat Ziganshin wrote:
{-# OPTIONS_GHC -fglasgow-exts #-}
main = do return xx = ((\x - print x) :: Show a = a - IO ())
main2 = do return xx = (\(x:: (forall a . (Show a) = a)) - print x)
main3 = do (x :: forall a . Show a = a) - return xx
print x
in this module, only main compiles ok
Simon Peyton-Jones wrote:
Another reasonable alternative is
data Set a = Eq a = Set (List a)
The type of member would become
member :: a - Set a - Bool
(with no Eq constraint).
John Hughes mentions this in section 5.2 of the paper, and points out a
problem: a function like
Ben Rudiak-Gould wrote:
Simon PJ thinks that Haskell' should include scoped type variables, and
I tend to agree. But I'm unhappy with one aspect of the way they're
implemented in GHC. What I don't like is that given a signature like
x :: a - a
there's no way to tell, looking at it in
From: Ben Rudiak-Gould [EMAIL PROTECTED]
Subject: Re: Bang patterns, ~ patterns, and lazy let
It's also not that case that !x has the same
meaning in both proposals, e.g.
let { !x = y ; !y = const 'a' x } in x
means 'a' in the current proposal but _|_ in yours.
Aargh,
John Meacham wrote:
however, (Set (a - a)) is malformed. since a _requirement_ is that Set
can only be applied to a type with an Eq constraint so the instance you
try to do something like
returnid :: Set (a - a) -- ^ static error! you need
returnid :: Eq (a - a) = Set (a - a)
the instant you
On Tue, Feb 07, 2006 at 07:59:46PM -0800, Ashley Yakeley wrote:
John Meacham wrote:
however, (Set (a - a)) is malformed. since a _requirement_ is that Set
can only be applied to a type with an Eq constraint so the instance you
try to do something like
returnid :: Set (a - a) -- ^ static
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