[Haskell-cafe] Lenses and records and ecosystem

[Fumiaki Kinoshita]

Are there any real cases that the polymorphism of Control.Category..
becomes a real problem? I think ambiguity rarely occurs on the kind (* -> *
-> *).

2017-02-10 14:35 GMT+09:00 Anthony Clayden <anthony_clayden at clear.net.nz>:

> I see Simon PJ's comment here
> https://github.com/ghc-proposals/ghc-proposals/pull/
> 6#issuecomment-277971802
> and the lengthy discussions from different advocates.
>
> How much is it true there's a fractured "Haskell ecosystem"
> with 2 (3?) incompatible approaches:
> * H98 style labelled records with various extensions to ease
> the pain.
> * newtype-wrapped Lenses
> * 'raw' (unwrapped) Lenses
>
> Can you mix those three styles inside one program? How much
> pain does it cause?
>
> Can you import libraries with a mix of styles? How does a
> program cope?
>
> I see the plethora of operators Lenses come with
>  (mostly to keep the types coherent?).
> Except that Lens composition is plain function composition
> (.).
>
> I remember something from SPJ's video/lecture on Lenses:
> that having Lens composition turn out to be function
> composition is "cute".
> That suggests to me it's more of a happy accident than a
> necessary feature.
>
> I also see in the ORF proposal, OverloadedLabels part,
> that composing with Control.Category.(.) can lead to type
> ambiguity.
>
> I wonder:
> Could there be a dedicated operator for composing Lenses,
> that has the same semantics as (.),
> but a more specialised type?
> To strengthen type inference/reduce ambiguity.
>
>
> AntC
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