On Tue, Jan 27, 2015 at 6:47 PM, Edward Kmett <[email protected]> wrote:
> > This works great for lenses that don't let you change types. > This is not the only restriction required for this to be an acceptable solution. As soon as you have a distinct Lens type, and use something Category-like for composition, you are limiting yourself to composing two lenses to get back a lens (barring a terrible mptc 'solution'). And that is weak. The only reason I (personally) think lens pulls its weight, and is worth using (unlike every prior lens library, which I never bothered with), is the ability for lenses, prisms, ismorphisms, traversals, folds, etc. to properly degrade to one another and compose automatically. So if we're settling on a nominal Lens type in a proposal, then it is automatically only good for one thing to me: defining values of the better lens type. -- Dan
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