Sign in to follow this  
proanim

array incrementation

Recommended Posts

proanim    455

I wanted to draw a grid with array of sprites. And I made it work with this code

// loop over each sprite, setting their textures
// grid
for(int i = 0; i < 20; i++)
{
	spr[i].setTexture(tex);
	spr[i].scale(sf::Vector2f(0.55f, 0.55f));

	// 1st row
	if(i < 10)
		spr[i].setPosition(105.6f * i, y);
	// 2nd row
	if(i > 10 || i < 20)
		spr[i+10].setPosition(105.6f * i, y + 52.8f);
	// 3rd row
	//if(i > 20 || i < 30)
	//	spr[i+20].setPosition(105.6f * i, y + 105.6f);

}

Now I want to optimize this code so I can use it more efficiently later. The code brakes if I set spr[i] instead of spr[i+10] in second if loop. Why is this? How can I continue through the array without +10 or whatever next to it?

Share this post


Link to post
Share on other sites
Vortez    2714

You just need to learn to use the modulo operator.

 

for(int i = 0; i < 30; i++)
{
    spr[i].setTexture(tex);
    spr[i].scale(sf::Vector2f(0.55f, 0.55f));

 

    spr[i].setPosition(105.6f * (i % 10), y + (52.8f * (i / 10)));

}

Edited by Vortez

Share this post


Link to post
Share on other sites
aregee    1072

Vortez solution is the way to go, but it seems you have a flaw in your logic:

 

    if(i < 10) //This will be run if i is less than 10
    if(i > 10 || i < 20) //This will be run regardless
    if(i > 20 || i < 30) //This will be run regardless

What you have written is exactly the same as:

 

    if(i < 10) //This will be run if i is less than 10
    if(true) //This will be run regardless
    if(true) //This will be run regardless

I think this is what you meant:

    if(i < 10) //This will be run if i is less than 10
    if(i >= 10 && i < 20) //This will be run if i is greater or equal to 10, but less than 20
    if(i >= 20 && i < 30) //This will be run if i is greater or equal to 20, but less than 30

EDIT: Although operator precedence ensures the correct order of operation in this case, I usually wrap the tests like this for ease of reading:

    if ((i >= 20) && (i < 30))
But that is probably just taste...  smile.png
Edited by aregee

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this