I've set up a repo for Pie code that I'm working on. The repo currently contains two files: TreeLib.pie (yesterday's code), and max.pie (which includes implementations of the max and monus function, along with supporting proof objects). The code in max.pie is obviously begging to be re-written as a single general function, along with the corresponding proof objects, which are then used to implement the rest.
Assuming you have an .ssh key registered with mit.cs.uchicago.edu, you can clone my repo via
git clone git@mit.cs.uchicago.edu:saks/pie.git