GADTs Meet Their Match: Pattern-Matching Warnings That Account for GADTs, Guards, and Laziness by Georgios Karachalias, Tom Schrijvers, Dimitrios Vytiniotis, Simon Peyton Jones:
Another great paper on a very useful incremental improvement on GADTs as found in Haskell, OCaml and Idris. Exhaustiveness checking is critical for a type system's effectiveness, and the redundant matching warnings are a nice bonus.
Optimizing Closures in O(0) time, by Andrew W. Keep, Alex Hearn, R. Kent Dybvig:
Looks like a nice and simple set of optimizations for probably the most widely deployed closure representation.
Dependent Types for Low-Level Programming by Jeremy Condit, Matthew Harren, Zachary Anderson, David Gay, and George C. Necula:
A conceptually simple approach to verifying the safety of C programs, which proceeeds in 3 phases: 1. infer locals that hold pointer bounds, 2. flow-insensitive checking introduces runtime assertions using these locals, 3. flow-sensitive optimization that removes the assertions that it can prove always hold.
You're left with a program that ensures runtime safety with as few runtime checks as possible, and the resulting C program is compiled with gcc which can perform its own optimizations.
This work is from 2007, and the project grew into the Ivy language, which is a C dialect that is fully backwards compatible with C if you #include a small header file that includes the extensions.
It's application to C probably won't get much uptake at this point, but I can see this as a useful compiler plugin to verify unsafe Rust code.
With Python 3.5 released, the thing that drew my attention is the support for asynchronous programming through PEP 0492 -- Coroutines with async and await syntax, which added awaitable objects, coroutine functions, asynchronous iteration, and asynchronous context managers. I found the mailing list discussions (look both above and below) particularly helpful in understanding what exactly is going on.
Guido van Rossum reminisces a bit about early discussions of generators in the Python community (read the other messages in the thread as well). I think we talked about the articles he mentions way back when. Earlier still, and beyond the discussion by Guido here, was Icon, a clever little language that I have a soft spot for. i don't think we ever fully assessed its influence on Python and other languages.
You can use the same code to generate assembly for Windows, Unix, and Golang assembly. The library handles the various ABIs automatically. I haven't seen this cool project before.
Among the cool features is the ability to invoke the generated assembly as regular Python functions. Nice.
Freer Monads, More Extensible Effects, by Oleg Kiselyov and Hiromi Ishii:
This looks very promising, and includes some benchmarks comparing the heavily optimized and special-cased monad transformers against this new formulation of extensible effects using Freer monads.
See also the reddit discussion.
Even though I'm not a big fan of Haskell, I'm pretty excited about this. It represents a trend where PL is finally taking holistic programmer experiences seriously, and a move toward interactivity in program development that takes advantage of our (a) rich type systems, and (b) increasing budget of computer cycles. Even that they are trying to sell this is good: if people can get used to paying for tooling, that will encourage even more tooling via a healthy market feedback loop. The only drawback is the MAS sandbox, app stores need to learn how to accept developer tools without crippling them.
Reagents: Expressing and Composing Fine-grained Concurrency, by Aaron Turon:
This is a pretty neat approach to writing concurrent code, which lies somewhere between manually implementing low-level concurrent algorithms and STM. Concurrent algorithms are expressed and composed semi-naively, and Reagents automates the retries for you in case of thread interference (for transient failure of CAS updates), or they block waiting for input from another thread (in case of permanent failure where no input is available).
The core seems to be k-CAS with synchronous communication between threads to coordinate reactions on shared state. The properties seem rather nice, as Aaron describes:
The benchmarks in section 6 look promising. This appears to be work towards Aaron's thesis which provides many more details.
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