How to use typedef in C++

In C++, the typedef keyword is used to create aliases for existing data types, to enhance code readability and maintenance.

They are particularly suitable for simplifying the declaration of complex types (such as those involving heavy use of pointers).

Additionally, they improve readability and also facilitate portability across platforms (for example, by creating aliases for variable types with different names).

Basic Syntax

The basic syntax of typedef is as follows

typedef data_type alias_name;

For example,

typedef unsigned long ulong;

Common Uses of typedef

Aliases for Simple Data Types

The most basic use of typedef is to create aliases for simple data types, such as int, char, float, etc.

typedef int entero;
typedef float real;
typedef char caracter;

Now, entero, real, and caracter can be used instead of int, float, and char, respectively.

Aliases for Pointers

typedef is especially useful for creating aliases for pointers, which can significantly enhance readability.

typedef int* intPtr;

Aliases for Structured Types

When working with structures (structs), typedef can greatly simplify usage and declarations.

typedef struct {
    int x;
    int y;
} Point;

Point p1;
p1.x = 10;
p1.y = 20;

Complex Types and typedef

For more complex data types, such as function pointers or arrays, typedef can make declarations much more manageable.

Function Pointers

Declaring function pointers can be particularly confusing. typedef can simplify this task.

typedef void (*CallbackFunction)(int, int);

void myFunction(int a, int b) {
    std::cout << "a: " << a << ", b: " << b << std::endl;
}

int main() {
    CallbackFunction callback = myFunction;
    callback(5, 10);
    return 0;
}

Arrays and Matrices

For arrays and matrices, typedef can also help us make declarations clearer.

typedef int Matrix3i[3][3];

Matrix3i matrix = {
    {1, 2, 3},
    {4, 5, 6},
    {7, 8, 9}
};