Passing References to const

Passing references to const is a best practice in C++ for several reasons:

1. It clearly communicates to other developers that the function will not modify the argument.
2. It allows the function to accept both non-const and const arguments. If you don't use const, you can only pass non-const arguments.
3. It can avoid unnecessary copying of large objects, which can improve performance.

Here's an example:

1#include <iostream>
2
3struct Vector {
4  float x;
5  float y;
6  float z;
7};
8
9void PrintVector(const Vector& v) {
10  std::cout << "Vector: (" << v.x << ", "
11    << v.y << ", " << v.z << ")\n";
12}
13
14int main() {
15  const Vector v1{1, 2, 3};
16  Vector v2{4, 5, 6};
17
18  PrintVector(v1);  // Okay, v1 is const
19  PrintVector(v2);  // Also okay, v2 is non-const
20}

1Vector: (1, 2, 3)
2Vector: (4, 5, 6)

If PrintVector didn't use const, it couldn't accept v1 as an argument.