class

[Lazlo]

I want to crate a square class

[Lazlo]

how to begin?

[codewalker]

You have already started!

You are calling ModificaCentru and InInterior, Interesecteaza etc from main.
You will need to declare, define these for square.

Read here http://www.cplusplus.com/doc/tutorial/classes/

[Lazlo]

#include <iostream>

class  square 
{
int width, height;

public:
	
	void ModificaCentru(width, height);
	int area()
	{
		return width*height;
	}
	void ModificaLatura(int x, int y)
	{
		width = x;
		height = y;
	}
	



};

[Lazlo]

Not ok
?

[Lazlo]

anibady

[keskiverto]

Your program seems to call four member functions of a square (and default constructor):
ModificaCentru()
ModificaLatura()
InInterior()
Interesecteaza()

What each of those four is supposed to do? Please, describe each function.

What attributes must a square object have in order to implement the four functions?

[Lazlo]

?

[keskiverto]

p1.ModificaCentru(0, 0);  \\ center of square
p1.ModificaLatura(10);    \\ side of square

p1.InInterior(4, 4);      \\ the value in the square is  (4,4)

Do you mean that the Modifica* functions change the square?

What do you mean by "value in the square"? Does a square have a value? How is the value set? Is it computed from "Centru" and "Latura"?

What does the function Interesecteaza() do?

Do the Centru (x,y) and Latura(z) mean that the four corners of the square are at:

(x-0.5*z, y+0.5*z) (x+0.5*z, y+0.5*z)
(x-0.5*z, y-0.5*z) (x+0.5*z, y-0.5*z)

[Lazlo]

Yes
intersecteaza====intersection

[keskiverto]

Fine. What does "intersection" mean for squares?

[Lazlo]

If p1is in p2 yes or no

[Lazlo]

anibady

[keskiverto]

You are too impatient. You cannot expect others to answer you promptly. "Bumping" a thread "up" too quickly is considered impolite. Furthermore, if you do provide only little bits of information at a time, the willingness to help is not very high.


Now, define precisely what does "p1 is in p2" mean. Does it mean that p1 is entirely inside p2? If so, then if p1 is in p2, the p2 would not be "in p1", because p2 is obviously larger than p1. (Unless the p1 and p2 are identical, i.e. have same Centru and Latura. Are they then in each other?)


In your examples the values are all integral. Furthermore, the Latura seems to be always an even value. Can you enforce those? Particularly, the Latura being even is significant, because then half of Latura is an integral value too.

If Latura is not even (or Centru is not integral), then half of Latura +/- Centru coordinatre becomes a fractional value. Floating point math is much trickier than what one intuitively expects.


You have to be able to express all the details exactly, because that is the only thing that the computer understands.

[dhayden]

This is an interesting problem. You can change the squares center and it's size. That might make you think that the square should record it's center and size, but I suggest that you don't go that way. Instead, record the square's top, left, bottom and right edges. It will make ModificaDCentura and ModificaLatura a little harder, but Interesecteaza() will be much easier.

So for a start, class square should look like this:

class square
{
    int top, left, bottom, right;

public:
	square() : top(0), left(0), bottom(0), right(0) {}
    void ModificaCentru(int x, int y);
    void ModificaLatura(int sz);
    bool Interesecteaza(const square &s2);
    bool InInterior(int x, int y);
    friend ostream & operator <<(ostream &, const square &sq);
};

ostream &operator<<(ostream &os, const square &sq)
{
    os << '(' << sq.left << ',' << sq.top << ") to"
       << '(' << sq.right << ',' << sq.bottom << ")\n";
    return os;
};

Note that I've added an output operator that displays the top-left and bottom-right corners of the square. This will really help in debugging. Add temporary code to main() that will print out the squares:

int
main()
{
    square p1;
    p1.ModificaCentru(0, 0);
    p1.ModificaLatura(10);
    cout << "p1= " << p1;

    if (p1.InInterior(4, 4))
	cout << "yes\n";
    else
	cout << "no\n";

    if (p1.InInterior(6, 4))
	cout << "yes\n";
    else
	cout << "no\n";

    if (p1.InInterior(-1, 4))
	cout << "yes\n";
    else
	cout << "no\n";

    square p2;
    p2.ModificaCentru(-5, -5);
    p2.ModificaLatura(2);
    cout << "p2= " << p2;
    if (p1.Interesecteaza(p2))
	cout << "yes\n";
    else
	cout << "no\n";
    p2.ModificaCentru(7, 7);
    cout << "p2= " << p2;
    if (p1.Interesecteaza(p2))
	cout << "yes\n";
    else
	cout << "no\n";
    p2.ModificaLatura(4);
    cout << "p2= " << p2;
    if (p1.Interesecteaza(p2))
	cout << "yes\n";
    else
	cout << "no\n";

    system("pause");
    return 0;
}

Okay, now comes the hard part. Sit down with a pencil and paper and figure out what ModificaCentru() and ModificaLatura() should do. Then translate that to code Run the program and look at the output from the bold lines above. Don't pay any attention to whether the other output is right. Just make sure that the square is modified correctly.

Once you have the square getting set right, you can try the intersection methods. Here are a couple of pointers:
- a point is inside a square if its x coordinate is between the left and right edges of the square, and it's y coordinate is between the top and bottom edges.

To see if they intersect, notice that if they don't intersect then one square must lie above, below, to the left or to the right of the other square. Check these 4 conditions and if they are all false, then the squares intersect.

[Lazlo]

I must put condicion
I need to be a simple to understend

[keskiverto]

Public forum posts do not help only the one that did ask a question, but potentially others too. It is considered to be rude, if one erases the content of older posts, like you have just done. Replies to your posts now refer to something that the reader cannot know or learn from.