Edward Kmett


Software Engineering Lead at S&P Capital IQ, Chair of the Haskell Core Libraries Committee

Edward spent most of his adult life trying to build reusable code in imperative languages before realizing he was building castles in sand. He converted to Haskell in 2006 while searching for better building materials. He now chairs the Haskell core libraries committee, collaborates with hundreds of other developers on over 150 projects on github, builds tools for quants and traders using the purely-functional programming-language Ermine for S&P Capital IQ, and is obsessed with finding better tools so that seven years from now he won’t be stuck solving the same problems with the same tools he was stuck using seven years ago.

YOW! Lambda Jam 2015 Brisbane

Discrimination is Wrong: Improving Productivity


This talk is a case study in library design in Haskell.

Fritz Henglein has shown through a number of excellent papers how to use “discrimination” to do lots of things in O(n): Sorting many more data types than you’d expect, table joins, etc.

In the process of optimizing this approach and wrapping it up in a form that can be easily consumed, we’ll take a lot of detours through the different ways you can think about code when optimizing Haskell.

  • We’ll need some category theory, from a deeper understanding of monoids to Day convolution.
  • We’ll need to consider final and initial encodings.
  • We’ll need to drift down to low level system concerns from building a custom foreign prim to nesting unsafePerformIO within unsafePerformIO.
  • We’ll need properties of laziness from productivity to IVars.

Along the way we’ll find and fix a small problem with the initial discrimination paper, which opens the door to streaming results, rather than having to wait until all the input is ready.