I'm with wren -1 on the overloaded boolean stuff, but definitely still +1 on
this proposal over all.
On Sat, Oct 15, 2011 at 9:00 PM, wren ng thornton
On 10/15/11 8:33 PM, Bas van Dijk wrote:
But an important question is: is it wise to treat booleans and bits equally? Because this would allow something like:
{-# LANGUAGE RebindableSyntax #-}
foo = if 1 then 2 else 3
Well, they're both Boolean algebras... But the big question is, or should be, what exactly are we trying to model with the Bits class? The current design is clearly aimed at modelling bitvectors, and just happens to support a few other things too. Given this initial design, it's not at all clear that it would be sensible to replace that with a model for Boolean algebras.
Indeed, if I were trying to model Boolean algebras, I'd probably start with some classes for semilattices and then move up to complemented distributive lattices from there. This would set the ground for a better handling of partial orders and repairing the inconsistency of Float/Double's Ord instances. Unfortunately, it's liable to crash into the folks extending Monoid and the like, and it's not entirely clear how best to reconcile their interaction.
Personally, I'm -1 for treating Bits like Bool in rebindable syntax. While some Bits instances could sensibly be treated as Booleans in conditionals, not all of them can. In particular, anything other than bivalent Boolean algebras is going to introduce ambiguity. If Bits can be Bools, it should be an opt-in system rather than extending if_then_else_ to incorporate all Boolean algebras in an unclear and ambiguous way.
-- Live well, ~wren
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