exprjit

Mathematical expressions evaluation using JIT compiler.

This is a simple parser that wraps NativeJIT library to compile and evaluate mathematical expressions.

Example:

ExprJIT expr;

// Compile expression
bool ok = expr("0.25 + 1.2e-3 * 5");
if (ok) {
    // Evaluate compiled expression
    auto res = expr();
    std::cout << "Result: " << res << "\n";
} else {
    std::cerr << "Error: " << expr.error() << "\n";
}

It is possible to use custom variables in expressions:

ExprJIT expr;

// Define variable x
expr["x"] = 0.0;

// Compile expression
bool ok = expr("3*x - 2");

// Evaluate compiled expression for a range of values of x
double x = 0.0;
while (x < 10.0) {
    expr["x"] = x;
    std::cout << x << " : " << expr() << "\n";
    x += 1.0;
}

There are some predefined functions available, like sqrt, sin, and cos:

ExprJIT expr;

expr["pi"] = 3.1415926;
bool ok = expr("sin(pi/4) + cos(pi/6) / sqrt(2)");
auto res = expr();
std::cout << "Result: " << res << "\n";

Native functions can be exposed and used in expressions as well:

double func(double x)
{
    return (x > 0.0) ?  0.5*x : -0.1;
}

...

ExprJIT expr;
expr["func"] = func;
expr["t"] = 0.1;
bool ok = expr("func(sin(t) + 1)");
auto res = expr();
std::cout << "Result: " << res << "\n";

All values in expression are treated and evaluated as double type.

The parser will evaluate constant expressions on the fly during compilation in order to minimize the JIT-generated code footprint.