Unit 2 Lab 2: Script Variables

MF: I worry that the mathematics required on this page would be non-trivial for our students. What if they haven't had any geometry?
MF: I love the animation, but will students know where to find the "sides" variarble for the blocks that use it?
GH Feedback: Here is one way to create a factorial block that takes a positive integer n and reports the value 1 × 2 × 3 × ... × (n - 1) × n. factorial block
Where is the for loop found? needs to be imported from a library - need some prompt help Import library > iteration, composition?
We need to mention that set is an "assignment statement". --MF and BH
GH Feedback 9/8/15: Overall the organization is not the best in terms of directing students to different parts of the page...the different green boxes continue the sequence from previous boxes even though they are different questions/problems - doesn't make sense.
In number 5 in the second green box, you refer to step 3 and step 5, but the lines aren't numbered...maybe add line numbers in Snap! or in the course guides?

Watch the video (or read the instructions that follow it) to see how to create, name, and set the value of a script variable.
1. To create the variable, use (in the variables tab, of course).
2. To name the variable, click on the orange a and type the name you want.
3. To set your variable's value, use . The down-arrow lets you select the variable you want (in this example, there's only one variable to choose).
4. Then set its value.
This script draws polygons with a random number of sides.

This script uses the value of sides twice, once in the repeat block to say how many times the move-and-turn combination should be done, and once in computing the angle to turn.
1. Make the script and run it several times to see what it draws.
2. Check your understanding: Why does it make sense to start the range of possible random numbers at 3?
3. Check your understanding: Where did the formula come from?
Challenge: Modify the script so that it also picks a size randomly, from 30 through 60 using only multiples of 10.
There are two ways to create a second script variable. You could use another script variables block or you could extend the one block, using the right-arrow

"U2Lab2Polygons"
Analyzing and debugging: Instead of setting a script variable, this script just uses the pick random block in the two places that need the random number. Before you build and run this script, try to figure out what is likely to go wrong.

You will sometimes find it useful to compute some expression using the current value of a variable and then set the variable's value to the result. Here is one way that might look in snap.

Here is one example.
1. Build it, try it, and figure out why says one thing in step 3 and a different thing in step 5.
2. Change the 5 to a 7 and predict what this script will do.
This script leads up to a more useful example.
1. Build it, try it, and figure out how it does what it does.
2. Change the times 5 to times 3 and predict what it will do.
3. Then change the repeat 2 to repeat 3.
4. Build a reporter block named .
  The script you created should help. Put the variables (base) and (exponent) in the right places inside that script.
  Your block should work like this:
  
  Make sure it also works for this case:
  Check (as always!) to make sure it works as you expect.
Here is another example.
1. Build it, try it, and figure out how it does what it does.
2. Change the code so that it puts in hyphens (-) where the vowels used to be.
3. Change the code so that it counts the vowels, counts all the letters (not including spaces), and ends with
  
  If you like, compare the results you get from similar length sentences in two different languages. You may get very interesting results.