I've never thought of one being shorthand for the other, really. Since they are logically equivalent (in my interpretation) I don't really care which one we regard as more primitive.
On Fri, Apr 18, 2008 at 9:26 AM, Martin Sulzmann <[EMAIL PROTECTED]> wrote: > Lennart Augustsson wrote: > > > To reuse a favorite word, I think that any implementation that > > distinguishes 'a -> b, a -> c' from 'a -> b c' is broken. :) > > It does not implement FD, but something else. Maybe this something else > > is useful, but if one of the forms is strictly more powerful than the other > > then I don't see why you would ever want the less powerful one. > > > > Do you have any good examples, besides the contrived one > > class D a b c | a -> b c > > instance D a b b => D [a] [b] [b] > > where we want to have the more powerful form of multi-range FDs? > > Fixing the problem who mention is easy. After all, we know how to derive > improvement for multi-range FDs. But it seems harder to find agreement > whether > multi-range FDs are short-hands for single-range FDs, or > certain single-range FDs, eg a -> b and a -> c, are shorthands for more > powerful > multi-range FDs a -> b c. > I clearly prefer the latter, ie have a more powerful form of FDs. > > Martin > >
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