Rhea is an incremental constraint solver based on Cassowary, originally developed by Greg J. Badros and Alan Borning. The main differences are:

• Allows the programmer to write constraints in a natural way
• Rewritten in C++11, fixes some bugs and memory leaks
• CMake instead of GNU Autoconfig
• Unit tests use the Boost Test Framework
• Uses Doxygen for documentation
• Expression parser based on Boost Spirit
• Does not have a finite domain subsolver

#include <rhea/simplex_solver.hpp>
#include <rhea/iostream.hpp>

main()
{
    rhea::variable x (0), y (0);
    rhea::simplex_solver solver;

    solver.add_constraints(
    {
        x <= y,
        y == x + 3,
        x == 10
    });

    std::cout << x << " " << y << std::endl;
    // Prints "10 13"
}

This software is alpha. It does pass all unit tests, but it hasn't been used in an actual application yet. Use at your own peril.

Rhea is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License version 3.