Introduction

GH Feedback 7/31: The idea behind recursive vs explicit is fine. The blocks are easy to read. The problem is the math portion. The average HS junior will have had limited exposure to recursively defined functions. They may be able to handle the linear functions intuitively since they have been exposed to arithmetic and geometric sequences. Working with recursive linear equations with their knowledge of expertise is going to be challenging. However, they will not be able to work with the exponential functions. The average HS junior will have taken Common Core Algebra and Geometry and will have ZERO experience translating form recursive to explicit functions in mathematics. This is not appropriate on a HS level. You do not provide any math instruction here. I would have to spend a few days teaching recursive and explicit functions in mathematics before even attempting this lab. This course was intended for the lay-person. The mathematics portion on this page will alienate students and put them off of programming at this very early level.
GH Feedback 7/30/15: Item #1 Asks students to download the code and figure out what it does. The project opens but there is no code in the project.

You've built and worked with recursive command blocks. Recursion can also be used in reporters. Thinking and programming with recursive reporters can often help solve otherwise complicated problems.

What exactly is Tony’s map block doing?

Derman: Yours is more complicated.
Sasha: But that pattern was easier to spot (for me).

This block takes two whole numbers as input. Download it and figure out what it does.

Episode 1:

Derman is staring at this table:

Input	Output
0	3
1	5
2	7
3	9
4	11
5	13

Tony: In this table, each output is 3 more than twice the input. I have a reporter that will match it.
2n+3

Just to be sure, I’ll try it:
map 2n+3 over [0,5]

Is Tony right?

Episode 2

Sasha is looking at Derman’s table from Exercise 2.

Sasha: I see another way to match the table. If you look down the Output column, each number is two more than the one above it. The only special case is the first row, which doesn't have a row above it, so we have to build in explicitly the fact that if the input is 0 the output should be 3:

Check Sasha's work.
Build Sasha-like (recursive) reporters that agree with each of these blocks on whole numbers.
In problem 4, you can check your blocks against the ones in the problem for a long time, but you can’t check them for all numbers. Are there any numbers for which there isn’t a match?
Build Tony-like reporters that agree with each of these blocks on whole numbers.

Teacher Feedback: Going from explicit to recursive is hard enough for linear problems; these last two problems that require quadratics are far too hard for high school students who haven't had algebra. These Z and X problems should be in a TIF. --MF

What's the biggest difference between the two blocks?
What are some similarities between them?
What does all but first of do?
Fill in the empty parts of the following definition so that the block reports a sentence containing all the whole numbers from a to b. Note that this question does not involve a list. The inputs are numbers; the reported value is a text string (a sentence). What should the block report in the base case? Where does the recursive call go?

Getting Started