[Haskell-cafe] Foldable for (,)
monkleyon at gmail.com
Wed May 3 18:06:41 UTC 2017
"Square root of negative one" doesn't make a lot of sense if you ignore
the context of complex arithmetic. And it appears to make even less
sense that this expression should have several different solutions. Yet
quaternions are used today to describe the rotation of robots.
In other words: Robots – more than meets the i! Robots are cool. Don't
hate on robots. Don't be uncool.
An analog is true for /Traversable/ and /Foldable/. Part of the missing
context here is that you can write generic functions and later plug in
things like the 1-tuple (/Identity/) and get cool things. Just look at
What the instances in question really show is that some operations are
transparent in relation to type-level products (i.e. tuples). A
different place that shows the same are functions like "first" and
"second" that you'll find in the context of profunctors, categories, and
arrows. There's more than meets the eye here, and part of the reason you
don't get to benefit a lot from it is that that's still an active area
of research. From my own gut feeling it may well be where part of the
future of programming lies. Which, in my eyes, is pretty cool.
But then I'm just a random type still in the process of folding Haskell
theory through my Identity.
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