[mercury-users] constructor class syntax

[Fergus Henderson]

On 02-Nov-1999, Michael Day <mikeday at corplink.com.au> wrote:
> 
> :- class ordered_container(C(T)) <= container(C), ordered(T) where
> 	[
> 		func lowest_element(C(T)) = T,
> 		func highest_element(C(T)) = T,
> 		...
> 		and so forth
> 	].
> 
> 
> Does that syntax look at all realistic, or possible?

I'm not sure what that syntax is supposed to mean.
How would it differ from say

	:- typeclass ordered_container(C) <= container(C) where
		[
			func lowest_element(C(T)) = T <= ordered(T),
			func highest_element(C(T)) = T <= ordered(T),
			...
			and so forth
		].

?
	
Anyway, here's some references to related work:

[1] John Hughes, Restricted Datatypes in Haskell. Appeared in the 1999 Haskell Workshop.
	<http://www.cs.chalmers.se/~rjmh/Papers/restricted-datatypes.ps>.
[2] Mark Jones, Type Classes and Functional Dependencies.
	<http://www.cse.ogi.edu/~mpj/fds.html>.

The bibliography for [1] probably has good references to prior related work.

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh>  |  of excellence is a lethal habit"
PGP: finger fjh at 128.250.37.3        |     -- the last words of T. S. Garp.
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