David Menendez wrote:
On Dec 11, 2007 9:20 AM, Duncan Coutts <[EMAIL PROTECTED]
<mailto:[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 classes declare defaults for a common
superclass.
My standard example involves Functor, Monad, and Comonad. Both Monad and
Comonad could provide a default implementation for fmap. But let's say I
have a type which is both a Monad and a Comonad: which default
implementation gets used?
I'm disappointed to see this objection isn't listed on the wiki.
Doesn't sound like a very big problem. That would just be a compile time
error ("More than one default for fmap possible for Foo, please reslve
ambiguity").
Jules
_______________________________________________
Haskell-Cafe mailing list
[email protected]
http://www.haskell.org/mailman/listinfo/haskell-cafe
