For Loop Woes

Unity Engine
1 
byte mag_max = 20;
new byte[] magazine = byte[3] {20,20,20};

byte Get_Best_Mag()
{
 byte best_mag = 0;

 for ( byte this_mag = 0; this_mag == magazine.Length - 1; this_mag ++ )
 {
  if ( magazine [this_mag] == mag_max )
  {
   return this_mag;
  }

 if ( magazine[this_mag] > magazine[best_mag] )
 {
  best_mag = this_mag;
 }

 }
 return best_mag;

}

It gives me a "Not all paths return a value" error when I try to do this. I'm probably doing something stupid, but can someone help?
2

Explain what you’re trying todo…

3

Are you sure this function gives you the error? Here it is again, with cleaner formatting.

byte Get_Best_Mag() {
    byte best_mag = 0;
    for ( byte this_mag = 0; this_mag == magazine.Length - 1; this_mag ++ ) {
        if ( magazine [this_mag] == mag_max ) {
            return this_mag;
        }
        if ( magazine[this_mag] > magazine[best_mag] ) {
            best_mag = this_mag;
        }
    }
    return best_mag;
}

Line 11 is guarantees you that your code returns a value in the end. I don’t see anything wrong with it. :face_with_spiral_eyes:

Also:

// Why this:
this_mag == magazine.Length - 1
// and not this:
this_mag < magazine.Length
// ?
4

It doesn’t return another index other than 0 even when the value at 0 is less than twenty.

5

I even put a Debug.Log() function in each loop block. BUT, when they should be getting called, I get no messages.

6

You’re doing this:

for(byte this_mag =0; this_mag == magazine.Length-1; this_mag ++){

While you should be doing this:

for(byte this_mag =0; this_mag <= magazine.Length-1; this_mag ++){

You’re using == comparrison to find when you need to break out of the loop, which is immideately.

To understand what’s going on, remember that a foor loop that looks like this:

for(int i = 0; i < myArray.Length; i++) {
    //Code goes here
}

Is essentially a nice way to write this:

int i = 0;
while(i < myArray.Length) {
    //Code goes here
    i++;
}

If we write what you wrote in that form, it should be easy to see that the loop never runs:

byte this_mag = 0;
while(this_mag == magazine.Length-1) {
    //code
    this_mag++;
}

Unless your magazine array is exactly 1 long, your loop will never run.

Also note that there’s no reason to use byte as the index in the for-loop. Hell, since you’re on a 32 bit engine, there’s no real reason to use it at all unless you’re planning on writing large amounts of small values to a file, or have some other weird edge case.

1 Like
7

^ I thought that’s what the issue was, but wasn’t entirely sure what is it he’s exactly doing…who uses bytes? lol. Please explain why you’re using bytes. I’d love to know.

8

Because they are the smallest variable aside from bool I think. I worry too much about costing performance for computers I suppose, but hey at least when I make stuff they are optimized out of the box, somewhat at least.

9

When you operate on bytes like this, they’re implicitly converted to integers - so with the casting and such, you’re actually losing performance.

1 Like