A math expression parser and evaluator
This class allows evaluating math expressions expressed as strings, including named variables and standard functions. It implements the Shunting-yard_algorithm.
Calculator calc("-3.5*cos(i*5)+pi*(-2+sqrt(i*pi^2))/3");
double y = calc.set("i", 25.5).compute();Constants pi and e are predefined, as are the functions abs, sqrt, sin, cos, tan, acos, asin, atan
exp, floor, ln, log.
You can also evaluate directly in one statement:
double y = Calculator::eval("-3.5*cos(i*5)+pi*(-2+sqrt(i*pi^2))/3", Dic<double>("i", 25.5));But if you need to evaluate the same expression many times with different variable values, this will be much slower as it has to parse the expression each time.
Requires the ASL library.
Benchmark
Summing -3.5*cos(i*5)+pi*(-2+sqrt(i*pi^2))/3 for i = 0 .. 10000, time per each expression evaluation
| Evaluation | Time (μs) | Relative time |
|---|---|---|
| Native | 0.012 | 1.0 |
| compute() | 0.219 | 18.5 |
| eval() | 4.374 | 370.1 |
| python | 0.760 | 58.4 |
| javascript | 0.050 | 3.8 |