Hi Simon, An interesting use case is my time-lens library. http://hackage.haskell.org/package/time-lens-0.3/docs/Data-Time-Lens.html
You can do things like >>> modL minutes (+5) (TimeOfDay 16 57 13) 17:02:13 But one has to be somewhat lenient about the lens laws here. Roman * Simon Peyton-Jones <simo...@microsoft.com> [2013-10-03 08:07:12+0000] > (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 > > _______________________________________________ > Libraries mailing list > librar...@haskell.org > http://www.haskell.org/mailman/listinfo/libraries > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe
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