Lenses for nested sum types e.g. Either. On 03/10/2013 6:08 PM, "Simon Peyton-Jones" <simo...@microsoft.com> wrote:
> (I sent this to ‘libraries’ but Kim-Ee suggested adding Café, where so > many smart people hang out.)**** > > ** ** > > Friends**** > > ** ** > > Some of you will know that I’ve promised to give a talk about Edward’s > lens library <http://hackage.haskell.org/package/lens> at the Haskell > Exchange <http://skillsmatter.com/event/scala/haskell-exchange> in London > next Wednesday (9th). I did this to give everyone (including me) a break > from GHC hackery, and also to force me to learn about this lens voodoo that > everyone is twittering about. Edward generously gave me quite a bit of > one-to-one attention last week (my hair is still standing on end), but this > message is to ask your help too.**** > > > *Specifically, I’d like to give some compelling use-cases*. If you are > using the lens library yourself, could you spare a few minutes to tell me > how you are using it? I expect to cover Lens and Traversal but not Prism. > **** > > ** ** > > The use-case everyone starts with is nested records, but I’d like to go > beyond that. The next levels seem to be:**** > > **· **Lenses as views of data that isn’t “really there” e.g. > regarding a record with rectangular coordinates as having polar coordinates > too.**** > > **· **Lenses and Traversals that focus on elements of finite maps > (Control.Lens.At)**** > > ** ** > > What else? I’m sure you are using them in all sorts of cool ways that I > would never think of, and I’d love to know.**** > > ** ** > > Please don’t tell me anything secret! To give everyone the benefit I may > just concatenate all the replies and send to you all, so please say if you > don’t want me to do that with yours. **** > > ** ** > > And don’t burn too many cycles on this...I don’t want to waste your time, > and I can always get back to you if I can’t understand what you say. > Sooner is better than later...Weds is coming.**** > > ** ** > > Simon “Edward’s prophet” PJ**** > > ** ** > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > >
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