Header Files

Template classes can not be compiled using the same method of compilation as a traditional header (.cpp) file. This is because it contains multiple classes. We use the hpp file to remedy this instead. Declare before use applies to templates.

List<int> list1; 
List<int> list2;

// The Compiler needs to see all the code prior to use because of this.

Hpp files are header implementation files, because of this we include the header file at the bottom of the h file, or Vice Versa.

// For the hpp
#include "list.h"

// ------------------ //

// For the .h file
// code goes here
#include "list.hpp"

We commonly have the .hpp at the bottom of the h file, so that the style is effectivly the same for the end user. We still only need to include the (.h) file for usage.

[!NOTE] Judge which to use based on if you are using templates or not.

References, Params, Returns

L-Value - Changable, Non Temporary R-Value - Temporary object or a value not associated with an object name

// R-Value - 5
// L-Value - Number
int Number = 5;

L-Value References, are done using a single address, or pointer &, *, etc R-Value References, are done using a double address, &&.

[!NOTE] Auto will deduce Const, meaning it may have advantages over declaring the type directly.

int x, y, z; // regular var
int& r = x; // Legal
int& r2 = x+y; // Illegal, Thats an R value
int && r = x+y; // Legal, R-Value Reference