How to evaluate a function directly?

Question

Title may not make any sense but I dont really know how to explain this. I have a class called polynomial and lets say I defined a polynome called p1 which is 2x+4. What I want to do is calculate p1(5) directly. I dont want anything like double calculate (polynomial) etc I want to be able to calculate my polynom with p1(x).

I hope my question is clear

Answer 1

Overload the function-call operator:

struct polynomial
{
    double a, b;
    polynomial(double m, double n) : a(m), b(n) { }  // represents "a * x + b"

    double operator()(double x) const
    {
        return a * x + b;
    }
};

Usage:

polynomial p(2.5, 3.8);

double val = p(1.0);