ANN: NY Haskell presents Edward Kmett on Lenses, Folds, and Traversals -- Wed., December 12

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ANN: NY Haskell presents Edward Kmett on Lenses, Folds, and Traversals -- Wed., December 12

Gershom Bazerman
The first NY Haskell Users Group meetup was a great success -- with
roughly sixty attendees and conversations that stretched far too late
for a weekday night. Video and slides are available for both the
Practical Data Processing and Cloud Haskell talks:

Slides on Practical Data Processing:
Slides on Cloud Haskell:
Source for Cloud Haskell:

We expect our next meetup will be equally exciting, at a bare minimum.
We're actively seeking cool talks and presentations. If you're not a
New York local, but may be passing through or are in the tri-state
area or thereabouts, and would like to present some code or research
with even tangentially real-world implications to an informed and
appreciated audience, please do get in touch :-)

Also, there will be a NY tech holiday party on December 11th, which we
are organizing along with other NY technology and PL groups. Details
are available at the on the meetup site: Finally, at some point, we will
probably cease to spam -cafe with announcements of all our events, so
even if you can't make it to the next few ones, registering at the
meetup site is the best way to stay on top of what we will have

- - - -

Lenses, Folds, and Traversals
presented by Edward Kmett

Wednesday, December 12, 2012
7:00 PM To 9:00 PM

Pivotal Labs, 841 Broadway New York, NY
(8th Floor)


Edward Kmett will introduce his lens library, which provides a highly
composable toolbox for accessing and modifying multiple parts of data

From simple beginnings, starting with building blocks such as fmap and
(.), we will build up combinators suitable for working with a wide
array of data structures. These generalize the notions you already
know how to use into a form that is easier to compose, and
simultaneously allow them to be used for monomorphic containers such
as Data.Text. All without compromising on your ability to reason about
them using laws!

Once we've built up some foundations, we'll do a bit of a deep dive,
exploring consequences of this design. We will discuss the efficient
generic programming programming framework exported by lens, and
type-safe Traversal-based zippers.

Familiarity with the Applicative and Traversable classes from the
Haskell base libraries will be helpful (links provided below), but a
basic understanding of the concepts will be introduced we go along.
Attendees should expect to be gobsmacked with a newfound appreciation
for the power of a little (or a lot of) abstraction.

Useful (but not mandatory) references:

The lens library and documentation:
A previous, more introductory talk on how to use the lenses Edward
Kmett wrote for the scalaz in the Scala programming language:
The original Applicative paper:
Lots of information on Traversable:
A write-up of this talk, as presented at the Bay Area Haskell Users

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