35 messages in org.haskell.haskell[Haskell] PROPOSAL: class aliases| From | Sent On | Attachments |
|---|---|---|
| John Meacham | Oct 12, 2005 7:41 pm | |
| Philippa Cowderoy | Oct 12, 2005 7:55 pm | |
| John Meacham | Oct 12, 2005 8:16 pm | |
| Wolfgang Jeltsch | Oct 13, 2005 5:48 am | |
| John Meacham | Oct 13, 2005 6:03 am | |
| Malcolm Wallace | Oct 13, 2005 6:15 am | |
| Andres Loeh | Oct 13, 2005 6:23 am | |
| Malcolm Wallace | Oct 13, 2005 6:29 am | |
| John Meacham | Oct 13, 2005 6:37 am | |
| John Meacham | Oct 13, 2005 6:39 am | |
| Simon Peyton-Jones | Oct 13, 2005 7:02 am | |
| Benjamin Franksen | Oct 13, 2005 7:26 am | |
| Benjamin Franksen | Oct 13, 2005 7:33 am | |
| S.M.Kahrs | Oct 13, 2005 7:37 am | |
| John Meacham | Oct 13, 2005 8:32 am | |
| Simon Peyton-Jones | Oct 13, 2005 9:23 am | |
| Udo Stenzel | Oct 13, 2005 9:46 am | |
| Jan-Willem Maessen | Oct 13, 2005 9:58 am | |
| Paul Govereau | Oct 13, 2005 1:21 pm | |
| Jacques Carette | Oct 13, 2005 1:52 pm | |
| John Meacham | Oct 13, 2005 4:45 pm | |
| John Meacham | Oct 13, 2005 6:13 pm | |
| John Meacham | Oct 13, 2005 6:21 pm | |
| David Menendez | Oct 13, 2005 6:49 pm | |
| John Meacham | Oct 13, 2005 8:33 pm | |
| aj...@spamcop.net | Oct 13, 2005 11:25 pm | |
| Ashley Yakeley | Oct 14, 2005 6:20 am | |
| Ashley Yakeley | Oct 14, 2005 6:31 am | |
| Wolfgang Jeltsch | Oct 14, 2005 9:46 am | |
| Wolfgang Jeltsch | Oct 14, 2005 11:44 am | |
| Wolfgang Jeltsch | Oct 14, 2005 11:47 am | |
| Remi Turk | Oct 14, 2005 2:05 pm | |
| Udo Stenzel | Oct 15, 2005 6:15 am | |
| Ross Paterson | Oct 27, 2005 6:58 am | |
| Wolfgang Jeltsch | Oct 28, 2005 7:05 am |
| Subject: | [Haskell] PROPOSAL: class aliases | |
|---|---|---|
| From: | Andres Loeh (lo...@iai.uni-bonn.de) | |
| Date: | Oct 13, 2005 6:23:52 am | |
| List: | org.haskell.haskell | |
One thought: how will class aliases interact with type inference? e.g. if a declaration contains only a call to 'foo', should we infer the constraint Foo a, or FooBar a? Can there ever be a situation where choosing the more specific dictionary could leave us without a 'bar' method at some later point in the computation? (cf. up-casting and down-casting in OO languages).
If I declare a function
baz :: Bar a => ...
and then pass it a value which actually has a FooBar dictionary rather than just a Bar, will the implementation be able to find the right offset in the dictionary for the 'bar' method? How? (I know jhc eliminates dictionaries at compile-time, but other implementations do not.)
The way I understand the proposal, there are no FooBar dictionaries ever. John said that this can be translated by a source-to-source translation, so internally, a FooBar dictionary *is* a Foo and a Bar dictionary.
How much static checking can be done before desugaring the code? Will it be possible to give sensible error messages, or will those mention the "internal" classes that the alias is supposed to hide?
Cheers, Andres