CODEWITHSUNDEEP
actionscript-3language-agnosticfor-loop
apscience
apscience

Reputation: 7273

For loops - Not check condition the first run?

I want to start my for loop at a certain number, and make it loop. Like this:

5, 6, 7, 8, 9, 10, 0, 1, 2, 3, 4

If the maximum number is 10 and it starts at 5.

The reason is because I want to loop through every tile in my game in a certain order (top to down, then go right).

I have tried the following but it skips one number:

for(var i = position[0]+1; i != position[0]; i++){
    for(var j = position[1]+1; j != position[1]; j++){
        if(j > 11){
            j = 0;
        }
        if(i > 23){
            i = 0;
        }
        if(levelMap[i][j] == type){
            return position;
        }
        trace("j" + j);
    }
    trace(i);
}

Thanks

Upvotes: 0

Views: 309

Answers (3)

paxdiablo
paxdiablo

Reputation: 882806

If you want a sequence like 5, 6, 7, 8, 9, 10, 0, 1, 2, 3, 4 (where the starting point can be any number in that set), you don't need fancy loop constructs.

You can just use a normal loop with the modulo operator, something like (pseudo-code since one of the tags was language-agnostic):

start = 5
for i = 0 to 10
    use_i = (start + i) % 11
    // do something with use_i rather than i.
next i

This will iterate use_i from 5 to 4, cycling back to 0 after 10.

Upvotes: 5

Jason Sturges
Jason Sturges

Reputation: 15955

This could be done with i alone; however, trying to use your example maybe something like:

package
{
    import flash.display.Sprite;

    public class Test extends Sprite
    {

        public function Test()
        {
            super();

            for (var i:uint = 0, j:uint = 5; i < 11; i++, j = (5 + i) % 11)
            {
                trace("j = " + j);
            }
        }

    }
}

Upvotes: 1

redhotvengeance
redhotvengeance

Reputation: 27886

Your question is a bit confusing, but I do see a couple of possible errors based off of the order of numbers you said you're trying to achieve.

First, if you want the highest possible number for j to be 10, your conditional should be for (j > 10), not for (j > 11). The way it is now allows for j to iterate as 11 once.

Next, in that same conditional, you'll want to set j to -1, not 0. This is because j will increment on the next loop, and setting it to 0 means on next loop j will actually equal 1, and skip the 0 iteration (which may be what you meant when you said it "skips one number"). So it'll be:

if (j > 10)
{
    j = -1;
}

Hope that helps.

Upvotes: 1

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