15. Custom Datatypes

The topics (typedef, struct, and the arrow operator ->) are all fundamental concepts in C and C++ and are used for defining and working with custom data types.

struct is a keyword used to define a new data type that groups together a set of related variables. It is a fundamental concept in C and C++ for creating complex data types.

typedef is a keyword used to create an alias for an existing type. It is often used with struct to create more readable and concise code.

The arrow operator -> is used to access members of an object pointed to by a pointer. It is a shorthand notation for accessing members of an object through a pointer, and is commonly used when working with complex data types.

These concepts are all related to defining and working with custom data types, and are essential for writing larger and more complex programs in C and C++. They are typically covered in the early stages of learning C and C++.

typedef and struct

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In C and C++, struct is a keyword used to define a new data type that groups together a set of related variables. Here’s an example of how to define a struct in C:

#include <stdio.h>
 
struct Point {
    int x, y;
};
 
int main() {
    struct Point p = {1, 2};
    printf("x = %d, y = %d\n", p.x, p.y);
    return 0;
}

In this example, we define a struct called Point that contains two integer fields, x and y. We then create an instance of the Point struct called p and initialize it with the values {1, 2}. Finally, we print out the values of x and y using the dot notation.

Now, let’s talk about typedef. typedef is a keyword in C and C++ that allows you to create an alias for an existing type. Here’s an example of how to use typedef with the struct we defined earlier:

#include <stdio.h>
 
struct Point {
    int x, y;
};
 
typedef struct Point Point_t;
 
int main() {
    Point_t p = {1, 2};
    printf("x = %d, y = %d\n", p.x, p.y);
    return 0;
}

In this example, we use typedef to create an alias for the struct Point type called Point_t. We can then use Point_t just like any other type, such as int or float.

Using typedef can make your code more readable and easier to understand, especially when working with complex data types.

Arrow Operator

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In both C and C++, the -> operator is also known as the “arrow” operator. It is used to access members of an object pointed to by a pointer. Here’s an example to illustrate how it works:

#include <iostream>
 
struct Point {
    int x, y;
};
 
int main() {
    Point p = {1, 2};
    Point* pp = &p; // create a pointer to the Point object p
 
    std::cout << pp->x << ", " << pp->y << std::endl;
 
    return 0;
}

In this example, we define a Point struct with two integer fields, x and y. We then create a Point object p with the value {1, 2}.

Next, we create a pointer pp that points to the p object. To access the members of the p object through the pp pointer, we use the -> operator.

So, pp->x is equivalent to (*pp).x, and pp->y is equivalent to (*pp).y.

The output of this program will be:

1, 2