Use C++ to evaluate a string. Support complex numbers, function names and variables.

string msg;
// eval with variables 'x' and 'y'
cout << eval("log(-2) * i + 2 $x ^ ($y - 1)", { "x", "y" }, { { 1, 2 }, { 3, 4 } }, &msg) << endl;
cout << eval("$x + $y", { "x", "y" }, { { 1, 2 }, { 2, 3 } }) << endl;
cout << eval("-arcsin(2 - i)") << endl;
// Mismatch of brackets error example
cout << eval("3 * ( 2 + 3 ]") << endl;

• Variable Names are started with the symbol $.
• +, -, *, /, ^ and normal maths function names are supported.
• Imaginary unit can be i, I, j or J.
• Brackets can be (), [] or {}.

Tips: If you have expressions continuously only with difference in variable values, i.e. num_list, you can first call to_postorder and store the postorder std::vector. Each time, calling eval_postorder only can be more efficient.

This project is the basis of the development of Fractal Designer 6 and is already used in Fractal Designer 5.6. This project is the core of syntax analysis in Fractal Designer project.

MIT Licence