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A comment on Lenses. Parent comment

Re:Lenses by WJW on Monday June 27, 2022 @04:14AM (#31891862)
Not to be a lens hater, but I would definitely flag it in PR review if someone came up with that instead of something like this:

    > sum $ map (fromMaybe 0) <some list of Maybe Int>
Possibly with a different default value for Nothings. A lot of the optics libraries seem to focus a lot on making the general case as easy as possible while overcomplicating the specific case. `sumOf (folded . folded)` does have some advantages in working for lists of other types but I question how often you would reuse such a function for different types the first place. It just doesn't come up all too often in my own code, perhaps it is different elsewhere.
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Re:Lenses by ParetoOptimal on Monday June 27, 2022 @09:16AM (#31894169)
> `sumOf (folded . folded)` does have some advantages in working for lists of other types but I question how often you would reuse such a function for different types the first place.

The common refactor here would be to Either:

  > sumOf (folded . folded) [Right 1, Right 2]
  3
I don't like the "unwrap the Maybe" or "get rid of the pesky monad in my way" intuition that fromMaybe and catMaybes give beginners.

> A lot of the optics libraries seem to focus a lot on making the general case as easy as possible while overcomplicating the specific case.

I kind of agree with this, but contend the universality of a single powerful and composable lens syntax simplifies things more overall even if it makes a single use site more complicated.

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Re:Lenses by ParetoOptimal on Monday June 27, 2022 @09:29AM (#31894326)
> `sumOf (folded . folded)` does have some advantages in working for lists of other types but I question how often you would reuse such a function for different types the first place.

Just remembered another refactor that comes up a lot for me:

Refactoring `[a]` to `NonEmpty a`. A lot of times this tightens your code up, but i find if the call chain is monomorphic to list most won't bother with the refactor.

So I like lens for pushing away from that level of monomorphism that is resistant to better architecture.

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