Welcome to Abra, a tensor algebra toolkit written in Ruby.
Abra is currently a work in progress. The aim is to write 
a flexible and extendable toolkit to make automated manipulation
of tensors an easy task. Algebra involving index contractions,
substitutions and other manipulations is a unique challenge, but it
lends itself well to an object oriented approach. Hopefully
working with the strengths and conventions of Ruby will lead us to
create a modern and very useable package.