using loops for drawing a checkers board

[Kubani]

Hello all,

This is the text of exercise 4 of chapter 12 of PPP;
Draw a checkers board: 8-by-8 alternating white and red squares.

Is there a way to use the loop for doing that code to minimize the size of the code?

[ajh32]

I presume you're using a GUI? What OS and what IDE are you using?

[Kubani]

My OS is Windows 7 and my IDE is visual studio 2012? Have you read the PPP and especially that chapter?

[ajh32]

Have you read the PPP and especially that chapter?

No.

Perhaps you could either provide the block of code in question or a link to it, if it is available online.

Thinking logically, you could have a function to draw a coloured square at the required screen coordinates. Then you just need to iterate through a matrix calling the function with the x and y coordinates for where the square is to be drawn, the size of a square side, and colour.

[Kubani]

This is the block I should write for that problem;

#include <Graph.h>
#include <Simple_window.h>

int main()
{
	Point t(100,100);
	Simple_window win(t, 600,400, "My window");

	Graph_lib::Rectangle r1(Point(20,20),20,20);
	 r1.set_fill_color(Color::red);
	 win.attach(r1);

	win.wait_for_button();
}

//************************* 

The code written in line 9 through 11 is for only one square. And for doing the exercise I should repeat that snip code for 64 times! and that was the reason that I thought about a loop.

[ajh32]

Go for it...

[cire]

I imagine it would look something like the following:

#include <deque>

#include <Graph.h>
#include <Simple_window.h>

typedef Graph_lib::Rectangle Rect ;

int main()
{
    Simple_window win(Point(100,100), 600, 400, "My window") ;

    std::deque<Rect> rectangles ;

    for (int x = 0; x < 8; ++x)
    {
         for (int y=0; y < 8; ++y)
         {
             Rect rect(Point(x*20, y*20), 20, 20);
             if ( y % 2 )
                  rect.set_fill_color( x % 2 ? Color::red : Color::black ) ;
             else
                  rect.set_fill_color( x % 2 ? Color::black : Color::red ) ;
             rectangles.push_back(rect) ;
             win.attach(&rectangles.back()) ;
         }
    }
    
    win.wait_for_button() ;
}

[Kubani]

Thank you "cire",
I haven't learned about #include <deque> or deque<Rect> rectangles ; until now in this book, so I can't use of them. But anyway, I appreciate your answer.

[cire]

I have a hard time believing you weren't introduced to containers of some sort by the time you hit that point in the book, although I can well believe you weren't introduced to the the deque.

You may treat it almost the same as a vector, although it avoids a problem in this code that a vector would not. (Mainly that a push_back may cause reallocation and therefore relocation of elements so that the address fed to win.attach() is no longer valid.)

[Kubani]

I have a hard time believing you weren't introduced to containers of some sort by the time you hit that point in the book

Yeah, I weren't introduced to that facility until now in this book!

When I recalled the vectors I immediately thought about some code like below:

int main() 
{
	Point t(100,100);
	Simple_window win(t, 600,400, "My window");

	vector<Graph_lib::Rectangle> VR(64);
	VR[0].(Point(20,20),20,20);
	 VR[0].set_fill_color(Color::red);
	 win.attach(VR[0]);
	 // some more codes.

	win.wait_for_button();
}

But it also faces errors in line 7.