[Haskell-cafe] ANNOUNCE: lens-family 2.0.0 anniversary edition!

Oliver Charles ollie at ocharles.org.uk
Fri Jul 19 14:57:48 UTC 2019

* '_Left' and '_Right' have been renamed as 'lft_' and 'rgt_'.

Why? I fail to see the benefit of such a breaking change.

On Fri, Jul 19, 2019 at 3:53 PM <roconnor at theorem.ca> wrote:
> In celebration of the 10th anniversary of Twan van Laarhoven's seminal
> blog post ``CPS based functional references''[1], I am releasing version
> 2.0 of lens-family[2] and lens-family-core[3] packages.  This new release
> continues to explore the design of Van Laarhoven style optics with new
> support for adapters, grates, grids[4], and prisms.
> To bring support to these new optics necessarily means moving a little
> further away from syntactic compatibility with Kmett's lens library.
> In particular, lens-family's 'under' is unrelated to Kmett's lens
> library's 'under' combinator.  Nonetheless the 'under' combinator plays
> a crucial role in lens-family as a dual to the 'over' combinator and
> this naming is hard to resist despite the conflict.
> This new version comes with some minor incompatibilities with the version
> 1.2 library that may require user updates.
> See <https://hackage.haskell.org/package/lens-family-2.0.0/changelog>.
> [1]<https://www.twanvl.nl/blog/haskell/cps-functional-references>
> [2]<https://hackage.haskell.org/package/lens-family-2.0.0>
> [3]<https://hackage.haskell.org/package/lens-family-core-2.0.0>
> [4]A grid is an optic that is both a grate and a traversal.
> --
> Russell O'Connor                                      <http://r6.ca/>
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