function that the user inputs coordinates x,y and find if the coordinates are inside the area of an-CodePudding

#include <stdio.h>
char dentroRetangulo(int v1x, int v1y, int v2x, int v2y, int x, int y);
int main()
{
    int a, b, c, f,d,g,x,y;
    char D, h;
    
    printf("== Coordinates of a rectangle ==\n");
    printf("Inform the coordinates of the left inferior corner : \n");
    scanf("%d %d", &a, &b);
    printf("Inform the coordinates of the superior right corner: \n");
    scanf("%d %d", &c, &d);
    printf("=== points ===\n");
    printf("inform the coordinates of the point (x,y)\n");
    scanf("%d %d", &f, &g);
    h = dentroRetangulo(a,b,c,d,f,g);
    
    if(h == D)
    {
        printf("O ponto(%d, %d) encontra-se dentro  do retangulo", x, y);
    }
    
        return 0;
}
    
char dentroRetangulo(int v1x, int v1y, int v2x, int v2y, int x, int y)
{
    char D;
    char B;
    char F;
    if(x>v1x && x<v2x || y> v1y && y<v2y)
    {
        return D;
    }

so basically, this function is about of checking if a point is inside of a rectangle with the inferior corner x,y coordinates being v1x and v1y, and the superior coordinates v2x and v2y, and in the main function the user is supposed to input x and y coordinates to verify if they are inside it, i'm kinda of a newbie in C, but i already lost 1 entire day trying to find out what i did wrong here and idk maybe i'm too stupid to not see what is going on wrong here

CodePudding user response：

You are trying too much in a single line... this one is too complex:

if(x>v1x && x<v2x || y> v1y && y<v2y)

and it's also wrong. It should be:

if(x>v1x && x<v2x && y> v1y && y<v2y)

But avoid such statements...

Keep things simple by writing more code lines.

But first notice that a function like this should return 0 (aka false) when the point is outside and 1 (aka true) when it's inside.

So to keep it simple do:

int dentroRetangulo(int v1x, int v1y, int v2x, int v2y, int x, int y)
{
    if (x < v1x) return 0;  // If the point is to the left, return 0
    if (x > v2x) return 0;  // If the point is to the rigth, return 0
    if (y < v1y) return 0;  // If the point is below, return 0
    if (y > v2y) return 0;  // If the point is above, return 0

    return 1; // The point is inside, return 1
}

One simple check on each line makes your code more simple.

And in main call it like

if(dentroRetangulo(a,b,c,d,f,g))
{
    printf("O ponto(%d, %d) encontra-se dentro  do retangulo", f, g);
}

CodePudding user response：

The posted code has some issues, but the main problem seems to arise from some basic misunderstandings.

// The following will declare, but WON'T initialize two variables
// of type 'char'. Here, D, is the NAME of the variable, not its content,
// which is indeterminated.
char D, h; 

// Here h is assigned the value returned by OP's function, which has the 
// exact same issue noted before. Its value will still remain indeterminated.
h = /* ... */;

// Comparing two variables with indeterminated values has undefined behavior.
if ( h == D ) { /* ... */ }

If the intent is to write a function that returns a char value of 'D' when a point is inside a rectangle or 'F' otherwise (maybe 'B' if it's on one of the edges), the following could be a possible implementation.

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

char point_rectangle_intersection(Point bottom_left, Point top_right, Point p)
{
    // Check if the point is outside.
    if ( p.x < bottom_left.x  ||  p.x > top_right.x  ||
         p.y < bottom_left.y  ||  p.y > top_right.y )
        return 'F';
    
    // Check if the point is on one of the edges.
    if ( p.x == bottom_left.x  ||  p.x == top_right.x  ||
         p.y == bottom_left.y  ||  p.y == top_right.y )
        return 'B';

    // The point is inside.
    return 'D';    
}