Cassowary is an incremental constraint solving toolkit that efficiently solves systems of linear equalities and inequalities. Constraints may be either requirements or preferences. Client code specifies the constraints to be maintained, and the solver updates the constrained variables to have values that satisfy the constraints.

This is a Ruby port of the Smalltalk version of Cassowary. The original distribution can be found here.

A technical report is included in the original distribution that describes the algorithm, interface, and implementation of the Cassowary solver. Additionally, the distribution contains toy sample applications written in Smalltalk, C++, Java, and Python, and a more complex example Java applet, the "Constraint Drawing Application".