Thread: Struct, points, square

Hi guys. I need to create a progam with struct of 4 points that define a square (and something more - that's why there are 3 structs, not one). The goal of the program is to check wheter those points form a real square.

Code:

#include <stdio.h> 
#include <math.h> 

void write();

typedef struct point
{
int x;
int y;
}

typedef struct square
{
point point1;
point point2;
point point3;
point point4;
}

typedef struct segment
{
point point5;
point point6;
}

int main() {

void write() {
printf("Enter x:\n");
scanf("%d", x);

Is it a good start?

After the declaration of a struct you must place a semicolon:

Code:

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

Also, both main() and write() have only opening accolades, {. they should have a } too.
For the rest this seems a good start to me (but I'm not a reference)

OK, but still there are a lot of errors...

Here's the list:
c: In function `write':
c:30: error: `x' undeclared (first use in this function)
c:30: error: (Each undeclared identifier is reported only once
c:30: error: for each function it appears in.)
c:32:2: warning: no newline at end of file

What laserlight says, is this:

Code:

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

point a, b;

Hey Jacek, did you think about the orientation of the square? I mean: does the bottom line has to be parallel with the X-axis? Or can the bottom line be at any angle?
This makes a whole difference. The first variant isn't too difficult to implement. The second one is not that easy (not for me).

Obviously the first one.

The problem is that I have no idea how to put x1..x4 and y1..y4 into this (I have already algorithm checking wheter 4 points for a square).

Hey, you make 4 objects of point, as you declared. Then you have to compare the x's and y's.

If you have 4 points, point_1, point_2, point_3, point_4, then you can access the x and y like this:

Code:

if (point_1.x == point_2.x){
/*do something*/
}

so, before that for example:

printf("Enter x1:\n");
scanf("%d", point1.x);
printf("Enter y1:\n");
scanf("%d", point1.y);

?

The second argument of scanf() has to be the address of a variable.

So what in my example?

Code:

scanf("%d", & point1.x);

& is the address-operator.

ok. so far i have this. it compiles, but doesn't check those 4 poinst...

Code:

#include <stdio.h> 
#include <math.h> 

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

typedef struct
{
  point point1;
  point point2;
  point point3;
  point point4;
} square;

typedef struct
{
  point point5;
  point point6;
} segment;

int main() {

  square s1;

  printf("Enter x1:\n");
  scanf("%d", & s1.point1.x);
  printf("Enter y1:\n");
  scanf("%d", & s1.point1.y);

  printf("Enter x2:\n");
  scanf("%d", & s1.point2.x);
  printf("Enter y2:\n");
  scanf("%d", & s1.point2.y);

  printf("Enter x4:\n");
  scanf("%d", & s1.point3.x);
  printf("Enter y3:\n");
  scanf("%d", & s1.point3.y);

  printf("Enter x4:\n");
  scanf("%d", & s1.point4.x);
  printf("Enter y4:\n");
  scanf("%d", & s1.point4.y);

// point (x1,y1) distance to (x2, y2) should equal distance from (x2,y2) to (x3, y3)
//assuming x1,y1 is the top left, x2,y2 is the bottom left
int square = 0;
//x3, y3 is the bottom right
if ( (s1.point2.y-s1.point1.y) == (s1.point3.x-s1.point2.x) )
        square++;
//x4, y4 is the top right
if ( (s1.point4.y-s1.point3.y) == (s1.point4.x-s1.point1.x) )
        square++;
 
if ( (s1.point4.y-s1.point3.y) == (s1.point2.y-s1.point1.y) )
        square++;
 
if ( (s1.point3.x-s1.point2.x) == (s1.point4.x-s1.point1.x) )
        square++;
 
if (square == 4)
        printf("It's a perfect square!");


}