Postponing sqrt Computations

This section will show you how to use a proxy object to postpone, or even avoid, using the computationally heavy std::sqrt() function when comparing the length of two-dimensional vectors.

A simple two-dimensional vector class

Let’s start with a simple two-dimensional vector class. It has $x$ and $y$ coordinates and a member function called length() that calculates the distance from the origin to the location $(x, y)$. We will call the class Vec2D. Here follows the definition: