Cadabra is described as 'Computer algebra system (CAS) designed specifically for the solution of problems encountered in field theory. It has extensive functionality for tensor computer algebra, tensor polynomial simplification including multi-term symmetries, fermions and anti-commuting' and is an app. There are more than 10 alternatives to Cadabra for a variety of platforms, including Windows, Linux, Mac, Web-based and BSD apps. The best Cadabra alternative is R (programming language), which is both free and Open Source. Other great apps like Cadabra are GNU Octave, SageMath, Mathematica and MATLAB.