Physics Collision Library

https://gist.github.com/HoraceBury/8538519

To help with the calculation of physics collision categories and masks there is an excellent table available:
http://forums.coronalabs.com/topic/2128-collision-filters-helper-chart/

If you would rather use names for your categories and have the masks generated for you, you can use this library.

It's simple: Just think of a category name for each object you have and create masks for all the objects to collide with.

This Gist includes the collisionslib.lua and a modified main.lua for the "CollisionFilter" sample from the Corona SDK samples directory.

To use the library:
local collisionslib = require("collisionslib")

To create a filter mask:
local redCollisionFilter = { categoryBits = collisionslib.getCategory("red"), maskBits = collisionslib.getMask("border","red") }