> > Lenses for nested ... types ...
>
Hi Simon/Edward/all,
The most compelling uses I've seen for lenses is back to Benjamin Pierce's
[et al] papers on "Updatable Views". I think this is where the 'theory'
started(?), although similar ideas had kicked around the relational
database world for
On 3 October 2013 10:57, Roman Cheplyaka wrote:
> 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 len
On Thu, 3 Oct 2013 22:06:22 +1000, Tony Morris wrote:
> Lenses for nested sum types e.g. Either.
I think those would be leaning more in the direction of prisms.
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Lenses for nested sum types e.g. Either.
On 03/10/2013 6:08 PM, "Simon Peyton-Jones" 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
Hi Simon,
http://hackage.haskell.org/package/lens-datetime-0.2/docs/Data-Time-Lens.html
Read the top of the page.
aDay = fromGregorian 2013 08 22
aLocal = LocalTime aDay (TimeOfDay 13 45 28)
aUTC = UTCTime aDay 7458.9
>>> aLocal ^. years
2013
>>> aUTC ^. months
8
>>> aDay ^. days
22
>>> aLocal
Another great use of lenses is the lens-aeson library (not to be
confused with aeson-lens). It's technically based around prisms, though,
so it's outside the scope of your talk; but you may wish to at least
reference it - it makes working with JSON really elegant!
__
Simon,
I've used lenses to manipulate URIs represented as strings in a structured way,
like:
modify (port . iso parsePrintUri) (+10) "http://localhost:8070/index.html";
Of course using fclabels and not lens ;-)
Sebastiaan
On Oct 3, 2013, at 10:07 AM, Simon Peyton-Jones wrote:
> (I sent th
Hi,
In a game I made recently, I had to load OBJ formatted models into an
OpenGL-friendly format. To do that, I'd parse the .obj, into a simple ADT,
and build the model into a vector. Here's where lens comes in: we want to
build separate vectors for the vertices, normals, UVs and faces indices.
le
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
Simon,
On Thu, 2013-10-03 at 08:07 +, Simon Peyton-Jones wrote:
> If you are using the lens library yourself, could you spare a few
minutes to tell me how you are using it?
I'm not a heavy 'lens'-user (yet), and this might not be the most pretty
use-case from a theoretic point of view, but an
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