Beautiful C++: 30 Core Guidelines for Writing Clean, Safe, and Fast Code

Chapter 1.5

ES.10: Declare one name (only) per declaration

Let me introduce you

A declaration introduces a name into the program. It can also reintroduce a name: multiple declarations are entirely permissible, for without them we would be unable to have forward declarations. A definition is a special kind of declaration, since it provides enough detail to be able to use the thing that has been named.

There are a surprising number of types of declaration. You can declare functions, like this:

int fn(int a);

This is a very common use of declarations. A name is being introduced, fn, which is of type “function taking an integer and returning an integer.” You can use this func-tion in your code without having to define it first. You can declare ...