[Haskell-cafe] Language extension proposal: aspects
Theodore Lief Gannon
tanuki at gmail.com
Mon May 8 22:51:05 UTC 2017
On Mon, May 8, 2017 at 1:16 PM, MarLinn <monkleyon at gmail.com> wrote:
> On 2017-05-07 05:19, Theodore Lief Gannon wrote:
> To avoid surprises, they shouldn't propagate -- when foldMap invokes even,
> it sees the default Monoid instance for Bool (i.e. none).
> That sounds like a gateway to inconsistency. I think the solution is that
> adding an aspect to, say, an Int would not apply that aspects to all Int's,
> but only to the ones unifying with the annotated one.
Hmm... this might work? As long as you can handle the situation where a
higher-order function depends on one instance, but a function passed to it
depends on another. (Consider Maybe, which has at least four legal Monoid
instances, one of which is default!)
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