Hi, 2011/6/21 Simon Peyton-Jones <simo...@microsoft.com>
> | One thing you could do to help in this specific case would be to use a > | different M1 tag--e.g., M1 S ... for selectors and M1 NS ... for > | fields without selectors (or K1 NS). I presume you've already > | considered this and/or it's too late to make such a change. (Or to > | move the distinction up to the constructor with two different > | constructor tags, CR and CN for record and no-record.) > > I don't think it's too late to make a change. The stuff has only just gone > in, so it's still very malleable. There may be other considerations, but > legacy code isn't one of them! > I suppose that could be changed, yes, but what exactly are we trying to solve here? One can already specify different behavior for constructors with/without named fields. Are we trying to avoid OverlappingInstances? Then yes, this might help, but I'm not sure this change alone would make all generic programming possible without OverlappingInstances. (Also, I always thought UndecidableInstances were "more evil", in some sense, and this change does nothing to remove the use of UndecidableInstances for generic programming.) Cheers, Pedro
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