Pre-Lecture Prep and Pre-Quiz

Please read up to "in class work" complete the pre-quiz before attending lecture.

Announcements

• The midterm exam is next Thursday. We will have a review session Tuesday.
  • Please complete the review problems before class Tuesday and come prepared with your questions!
• Office hours and wizard sessions:
  • Delano: Wednesdays at 3pm-5pm EDT (same zoom link as lecture), or by appointment
  • Cheever: check his schedule
  • Ruether: by appointment Wednesdays 10am-12pm, Thursdays 3pm-5pm EDT (link)
  • Wizard sessions: Sunday 1-3pm EDT, Monday 7-9pm EDT (zoom link on moodle)

Learning Objectives and Outcomes

In this lecture, you will...

• read a short lecture about using for loops
• complete in class problems using for loops to turn different sequences of neopixels on and calculate the Fibonacci sequence

By the end of this lecture, you should be able to...

• Use for loops to turn an arbitrary combination of neopixels on
• Use for loops to calculate values in mathematical sequences

For Loops

A for loop is a special type of while loop with a different syntax. The syntax is most easily explained by an example. Compare these two pieces of code:

// 1 - initialize
byte count = 0; 

// 2 - check condition
while (count < 4){

	//execute code
	Serial.println(count);
	//3 - increment
	count++;
}

// 1 - initialize; 2 - check; 3 - increment
for (byte count = 0; count < 4; count++){
	Serial.println(count);
}

In the while loop case, the variable count is set to 0 (step 1 - initialize). Then the condition count < 4 is checked (step 2 - check condition), and the loop counts 0, 1, 2, 3, incrementing by one each time (step 3 - increment). The for loop implementation is just a condensed version of the code on the left; the initialization step, the check condition step, and the increment step are all on a single line at the top. The initialization step always happens first, the condition is always checked each iteration of the loop, and the variable is always incremented at the end of the loop.

We can use whichever values we want to the initialization, check, and increment stages. We can potentially even leave some of them blank! For example, to count down from 10 to 0:

for (int count = 10; count >= 0; count--){
	Serial.println(count);
}

// how to do this as a byte?
// ideas:
// - use an extra condition (check when we get to zero to make sure we don't dec)
// - count >= 255 (not quite)
// - count < 255 (also works, use equivalent of -1 for number of bits)
// - for (byte count = 11; count >=1; count--) {Serial.println(count-1)} <- easiest
for (int count = 10; count >= 0; count--){
	Serial.println(count);
}

<aside> ❓ Why did we need to switch to using an int? How could this be implemented using a byte?

</aside>