[Haskell-cafe] Lenses and records and ecosystem

Anthony Clayden anthony_clayden at clear.net.nz
Fri Feb 10 05:35:13 UTC 2017

I see Simon PJ's comment here
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

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.


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