ft_point.h

Create a file ft_point.h that’ll compile the following main:

#include "ft_point.h"

void  set_point(t_point *point)
{
point->x = 42;
point->y = 21;
}

int main(void)
{
  t_point point;
  set_point(&point);
  return (0);
}

We have to define a structure t_point with x and y as its members:

#ifndef FT_POINT_H
#define FT_POINT_H

typedef struct s_point
{
  int x;
  int y;
} t_point;

#endif

[!TIP] If you don’t understand this, see if reading SIMPLE helps you understand it better.

Explanation:

#ifndef FT_POINT_H

This line checks if the preprocessor macro FT_POINT_H is not defined. The #ifndef directive stands for “if not defined”. This is the first part of an include guard, which prevents the code within the guard from being included more than once in a single compilation. (We are checking if we have not defined FT_POINT_H before. If we haven’t, we will do some stuff next.)

#define FT_POINT_H

If FT_POINT_H is not defined, this line defines it. The purpose of this is to ensure that the following code is only included once, even if this header file is included multiple times in different files. (We now define FT_POINT_H so that next time we know we have already done this and won’t do it again.)

typedef struct s_point
{
  int x;
  int y;
} t_point;

• typedef is a keyword used to create an alias for a data type, making it easier to use. (lets us make a nickname for a type.)
• struct s_point defines a structure with the tag s_point. A structure in C is a user-defined data type that groups related variables.
• { int x; int y; } are the members of the structure. Here, x and y are both integers that represent coordinates in a 2D space.
• t_point is the alias name for the structure struct s_point. This means you can use t_point instead of struct s_point when declaring variables of this type, making the code cleaner and easier to read. (We call this group t_point so we can use this shorter name instead of the longer struct s_point.)

  #endif
  

  This line ends the conditional started by #ifndef. If the file has not been included before, the code between #ifndef and #endif is included. If it has been included before, it is ignored. (This ends our check. If we haven’t added this file before, we do it now. If we already did it, we skip everything between #ifndef and #endif.)

Name	File Image
ft_point.h
main.c

[!TIP] If you don’t understand this, see if reading SIMPLE helps you understand it better.

[!TIP] Clic here to visualize the execution.