Bears some resemblance to the Thimbleby calculator: http://www.cs.swan.ac.uk/calculators/how.html http://www.cs.swan.ac.uk/calculators/how.html Both have you

Bears some resemblance to the Thimbleby calculator: http://www.cs.swan.ac.uk/calculators/how.html http://www.cs.swan.ac.uk/calculators/how.html Both have you write numeric expressions and then manipulate them while the calculator solves the constraints 'live'; how they developed that general idea differs.