Trouble Understanding x++ and y++ Coding

[PrecentralGyrus]

Hey guys,

I know I just posted a post asking for help on a different subject, but I've narrowed down what I am confused about. I don't fully understand how the x++ and y++ commands work. Here is example coding:

Code: Select all

int y = boxY;
	while( y < boxY + boxWidth )
	{
		int x = boxX;
		while( x < boxX + boxWidth )
		{
			gfx.PutPixel( x,y,255,255,255 );
			x++;
		}
		y++;
	}
}

This creates a square, and I understand how everything works, except how the x++ and y++ commands make the entire square. With this coding I would expect the computer to draw a line from the PutPixel coordinates right, along the x axis, until it hits boxX + boxWidth, and draw a line down, along the y axis, until it hits boxY + boxWidth, and not fill in the rest of the square.
How is the rest of the square filled in with this simple command?

Thanks!

[cameron]

x++ means x = x + 1; and y++ means y = y + 1;

[PrecentralGyrus]

x++ means x = x + 1; and y++ means y = y + 1;

Yeah, but I don't see how that fills in an entire square. With that coding, shouldn't it just create two lines from the PutPixel coordinates on the x and y axis's, instead of filling in an entire square?

[Freeman]

what youre having trouble understanding is not the x++ and y++ commands, but rather the fact that the loops are nested. so whats basically happening is your inner loop always creates a single horizontal line ( read: place dots in a row until while criterion is met ), once it has reached the end, its told to move one space down and reset ( i.e. run through the first loop AGAIN, just with a different starting point ), this keeps on going until your 2nd while criterion is met

[PrecentralGyrus]

what youre having trouble understanding is not the x++ and y++ commands, but rather the fact that the loops are nested. so whats basically happening is your inner loop always creates a single horizontal line ( read: place dots in a row until while criterion is met ), once it has reached the end, its told to move one space down and reset ( i.e. run through the first loop AGAIN, just with a different starting point ), this keeps on going until your 2nd while criterion is met

Ah ok, I understand now. Thanks!

[DreamBliss]

There is also ++x and ++y to confuse you even more...

[albinopapa]

There is also ++x and ++y to confuse you even more...

...and what does that do?

[DreamBliss]

It, as far as I understand, pre-incriments x and y. So in the case of x++ what is really being said is x = x + 1. This increments x by 1, after this bit of code is executed.

But in the case of ++x I guess it's like saying x + 1 = x. It increments it first and asks questions later.

I hope that clarifies things.

I only know about this because of the book, "Exploring C++", which I got as my introductory/review text for C++. The author describes himself as a, "professional stunt programmer."

[albinopapa]

I had to look up examples but now I get it.

If you have y = x++ and y = ++x you get different values for y.
The former returns what x was before adding 1 and the latter returns x after adding 1.

[LuX]

http://www.planetchili.net/forum/viewto ... 361&p=4098

Scroll a few posts down. There's a huge ass post explaining the loop stuff.