Simon Peyton-Jones wrote:
Given instance C T where ..., for any method 'm' not
defined by ...:
for every class D of which C is a superclass
where there is an instance for (D T)
see if the instance gives a binding for 'm'
If this search finds exactly one
Simon Peyton-Jones wrote:
Concerning (b) here's a suggestion. As now, require that every instance
requires an instance declaration. So, in the main example of
http://haskell.org/haskellwiki/Class_system_extension_proposal, for a new data
type T you'd write
instance Monad T where
I had it pretty well worked out for single parameter type classes, but I
couldn't see any nice extension to multiple parameters.
On Dec 11, 2007 5:30 PM, Simon Peyton-Jones [EMAIL PROTECTED] wrote:
| If it really would work ok we should get it fully specified and
| implemented so we can fix
On Tue, Dec 11, 2007 at 02:20:52PM +, Duncan Coutts wrote:
I'd just like to float an idea that's related to the Class Alias
proposal[1] but is perhaps somewhat simpler.
We all know that Functor should have been a superclass of Monad, and
indeed we now know that Applicative should be too.
On Dec 11, 2007 9:20 AM, Duncan Coutts [EMAIL PROTECTED] wrote:
So my suggestion is that we let classes declare default implementations
of methods from super-classes.
snip.
Does this proposal have any unintended consequences? I'm not sure.
Please discuss :-)
It creates ambiguity if two
On Tue, 2007-12-11 at 07:07 -0800, Stefan O'Rear wrote:
This is almost exactly the
http://haskell.org/haskellwiki/Class_system_extension_proposal; that
page has some discussion of implementation issues.
Oh yes, so it is. Did this proposal get discussed on any mailing list?
I'd like to see
Duncan Coutts wrote:
On Tue, 2007-12-11 at 07:07 -0800, Stefan O'Rear wrote:
This is almost exactly the
http://haskell.org/haskellwiki/Class_system_extension_proposal; that
page has some discussion of implementation issues.
Oh yes, so it is. Did this proposal get discussed on any mailing
On Tue, Dec 11, 2007 at 04:26:52PM +, Simon Marlow wrote:
Duncan Coutts wrote:
On Tue, 2007-12-11 at 07:07 -0800, Stefan O'Rear wrote:
This is almost exactly the
http://haskell.org/haskellwiki/Class_system_extension_proposal; that
page has some discussion of implementation issues.
Oh
| If it really would work ok we should get it fully specified and
| implemented so we can fix the most obvious class hierarchy problems in a
| nice backwards compatible way. Things are only supposed to be candidates
| for Haskell' if they're already implemented.
Getting it fully specified is the
On Tue, 2007-12-11 at 16:38 +, Ross Paterson wrote:
On Tue, Dec 11, 2007 at 04:26:52PM +, Simon Marlow wrote:
Duncan Coutts wrote:
On Tue, 2007-12-11 at 07:07 -0800, Stefan O'Rear wrote:
This is almost exactly the
http://haskell.org/haskellwiki/Class_system_extension_proposal;
Simon Peyton-Jones wrote:
b) having instance declarations silently spring into existence
Concerning (b) here's a suggestion. As now, require that every instance
requires an instance declaration. So, in the main example of
http://haskell.org/haskellwiki/Class_system_extension_proposal, for a
On Dec 11, 2007 1:29 PM, apfelmus [EMAIL PROTECTED] wrote:
Without the automatic search, this is already possible
class Functor f where
fmap :: (a - b) - f a - f b
class Functor m = Monad m where
return :: a - m a
(=) :: m a - (a - m b) - m b
--
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