Loop Variant Relations

Proving that a loop always terminates is a common requirement when verifying software. The usual approach to doing this is to provide a loop variant function. This is typically an integer expression which decreases on every iteration of the loop.

Loop Invariants and Do/While Statements

Recently, I encountered what I thought was a bug in the Whiley Compiler. The issue related to the current treatment of do/while loops and loop invariants. Having now spent a fair bit of time researching the issue, the answer is not so clear.

Flying the CrazyFlie Quadcopter!

Last week, my CrazyFlie nano-quadcopter finally arrived and, since then, I’ve been learning how to fly! The copter is much smaller than I was expecting, and it requires you to solder a few bits together.

Thoughts on Parsing Whiley (and Indentation Syntax)

Recently, I have been reworking the Whiley compiler’s parser to make it more robust. Doing this has opened up some interesting issues, which I thought were worth discussing. Whiley uses indentation syntax without explicit end-of-statement terminators (e.

The Dafny Tutorial at SPLASH'13

Today I was attending the Dafny tutorial given by Rustan Leino at SPLASH'13. I have to say that this was the highlight of the conference for me. In case you haven’t come across it before, Dafny is a programming language designed for software verification.