Fall 2016 PL Junior Retrospective

:: PL Junior, by Ben Chung, by Milo Davis, by Ming-Ho Yee, by Sam Caldwell

The Programming Language Seminar, Junior (or “PL Junior”), is a seminar for junior students to learn and discuss topics at a pace more suitable to our background. This semester, we decided to study dependent types. We chose this topic because

  1. working from the TAPL presentation of type systems, dependent types are a step up in difficulty (excepting F-omega-sub), and
  2. they represent a significant increase in the reasoning power of types over programs.


:: by Gabriel Scherer

Max New, Daniel Patterson and Ben Greenman recently wrote three two-page abstracts on what they are working on right now. Come have a look — and any feedback is welcome!

Understanding Constructive Galois Connections

:: icfp, galois connection, adjunction, category theory, math, by Max New

One of my favorite papers at ICFP 2016 (in lovely Nara, Japan) was Constructive Galois Connections: Taming the Galois Connection Framework for Mechanized Metatheory by David Darais and David Van Horn. The central technical result is quite interesting, but a little intimidating, so I’d like to share a “de-generalization” of the result that I found helpful to understand.

Beta Reduction (Part 1)

:: lambda, calculus, beta, reduction, semantics, by Milo Davis

The λ-calculus is often introduced by showing how to build a real programming language from it’s simple syntactic forms. In this series of post, I attempt to introduce it as a tool for modeling semantics. So if you’re opening Barendregt for the first time, trying to understand a lecture from a programming languages or functional programming class, or just starting to become involved in PL research, I hope this post will help you understand evaluation by substitution (β-reduction).

History of Actors

:: history, by Tony Garnock-Jones

Christos Dimoulas is currently teaching a “History of Programming Languages” class at Harvard. The class is, as Christos writes, “definitely not about this”; instead, each meeting is a deep examination of a single, mature research topic, in terms of three to five key papers from the literature.

On Monday, I presented “the History of Actors” for the class. I’ve made the written-out talk notes and an annotated bibliography available here.

Emacs daemon for fast editor startup

:: System Administration, Emacs, by Gabriel Scherer

In the early days of the famous Emacs/Vim debates, Emacs was often ridiculed for its bulkiness (Eight Megabytes-of-RAM And Constantly Swapping, etc.). The computational power of our computer has grown much faster than Emacs’ bloat: it takes exactly one second to load on my machine. However, our workflows have also changed, and my workflow implies frequently starting new text editors — on each git commit for example, or when I use a Firefox extension to edit a textarea content in a proper editor.

In this blog post, I describe how to use emacsclient to reuse an existing Emacs process when creating a new editor window, which reduces editor startup times from 1s to 0.150s on my machine.