Loops

Loops are a powerful tool that allow us to "loop" through a segment of code with out having to write that segment over and over again. Like I have said countless times before, programmers are lazy, and this is just more proof.

While Loops

If we want to repeat a given block of code over and over again we can use a while loop. This will execute anything within its scope until the supplied condition becomes false. These are typically used for long running loops with an unknown number of iterations. It is important to have a condition within your loop that will allow it to end. If the condition remains true the loop while run till the end of time 👴.

boolean want_loop = true;
while(want_loop){
    /* do something to update the other
       condition */

    if(/* some other condition */) {
        want_loop = false;
    }
}

DO NOT USE WHILE LOOPS IN ROBOT CODE!!!

while loops are very dangerous in a controls application. If for some reason you forget to setup your exit condition correctly or your iterator increment is wrong you can get stuck in a infinite loop. This will lock up your entire robot program. That means while your code may still be "running" your robot will sit still and not respond to any inputs.

Increment Operators

There are a few more operators that may be helpful for looping through code. They are called increment operators. They purpose is assignment and arithmetic within a single simple operator. The two new operators can be seen in the table below.

Operator	Description	Compatible Datatypes	Example
++	Increment	int, double	int x = 0; x++; // x = 1
--	Decrement	int, double	int x = 0; x--; // x = -1

These are typically used in loops as an iterator to keep track of how many times a segment of code has been executed. They are for common in for loops, but can be used anywhere in your code.

For Loops

When we have any idea how many times we want to loop through a specific segment of code we can use a for loop. There are much safer, because they are structured to force a developer to thing about what happens to their iterator each loop and what the exit condition looks like. There are three segments to a for loop definition.

• Initialization: Run once when the for loop starts. This is only run once and typically is used to set the initial state of the iteration variable
• Condition: Stop condition that is checked at the start of each cycle of the loop.The condition typically includes some sort of logic check against the iteration variable.
• Update: Run after each cycle of the loop. It is typically used to update the iteration variable.

Syntax

for(initialization; condition; update){
   // Code to run each loop
}

Code Example

for(int i = 0; i < 500; i++){
    // Run this code 500 times
}

Break and Continue

Inside of a loop you can use certain keywords to skip a single loop or even stop the looping altogether.

• break: This allows you to "break out" of the entire loop structure and stop the looping behavior.
• continue: This will stop executing all remaining code in that given loop iteration and skip to the next iteration.

for(int i = 0; i < 500; i++){
   if(/* If we want to exit the loop NOW */){
       break;
   }

   if(/* If we want to SKIP to the next */){
       continue;
   }
}