On Tuesday 31 January 2006 01:37, Andrew Pimlott wrote: > On Tue, Jan 31, 2006 at 12:57:18AM +0100, [EMAIL PROTECTED] wrote: > > Quoting Andrew Pimlott <[EMAIL PROTECTED]>: > > >On Mon, Jan 30, 2006 at 11:06:29PM +0100, [EMAIL PROTECTED] wrote: > > >>So I envisage that you'd turn off the warning in the same way as > > >>you turn off the M-R today: by a type signature. > > > > > >But if people were happy adding type signatures for every > > > polymorphic variable definition, they wouldn't be moving to > > > eliminate the M-R, would they? Or do I misunderstand? > > > > Well, my feeling is that the M-R is an ugly wart, and I want it > > gone. But I'm still happy to put a type signature when I want > > something to be polymorphic. > > Ok, I understand your position now. But even given this view, I > think the warning will be problematic. First, when will the warning > be emitted? For all variable assignments without signatures, or only > for those that the implementation fails to monomorphize (as an > optimization)? The first is heavy-handed;
Agreed. > the second, obviously > implementation-dependent (someone using another implementation, or > another optimization level, will get the warning and will lose > sharing). And what, if I may ask, is the problem with that? I mean, I am used to different implementations having, sometimes drastic, differences in speed or memory use. Getting a warning about possible loss of efficiency due to loss of sharing might be /very/ helpful; and it can safely be ignored by a beginner, as long as it is unmistakenly flagged as such (i.e. an efficiency warning, nothing /wrong/ with the code). Furthermore, you would turn on such a warning only if you are expressly interested in your program's efficiency. And in this case I would be thankful to get as many (substantial) warnings as possible. > Second, a warning about "loss of sharing" may befuddle > beginners (who are usually not taught to write type signatures at the > start). > > Well, maybe when someone implements this warning, we will find out > I'm wrong and it doesn't cause trouble. And I agree with removing > the M-R, with or without the warning. I would make it a strong recommendation for implementations to provide a warning about loss of sharing due to 'accidental' (=inferred) polymorphism/overloading, whenever it /actually happens/. But I would demand that it is not turned on by default, so as not to unsettle the unsuspecting beginner. Ben _______________________________________________ Haskell-prime mailing list Haskell-prime@haskell.org http://haskell.org/mailman/listinfo/haskell-prime
