Loops
Objectives	Students will create looping program structures through the use of `repeat` and `forever` blocks. Students will implement increment/decrement operations through looping. Students will compare/contrast `if` with `repeat until` blocks to simulate decisions. Students will complete a fully functioning interactive Rock, Paper Scissors game that: incorporates random selection for the AI opponent, utilizes user input for player choices, and resolves wins through nested `if/else` blocks.
Activities	Experiment with Drawing Commands and Experiment With Repeat Students will experiment with the pen commands blocks in Scratch to draw simple line drawings. Direct students to Experiment With Drawing Commands. Instruct students to read and familiarize themselves with the layout before proceeding to Experiment With Repeat. Students will read a brief introduction of `repeat` loops and extend sample code to draw the following: Equilateral Triangle Pentagon Hexagon Octagon Circle Five-sided Star Homework: Repeat after me Students will practice thinking about the application of conditionals and loops in other contexts. Student will complete the ungraded quiz entitled Repeat after me. ------------------------- Check-in: Repeat after me Students will reflect on the idea of loops as presented in Repeat after me. Direct students to read through and answer the questions in Repeat after me. Discuss: In order for a repetition to be reproduced unambiguously, what 3 attributes are needed to convey the proper instructions? Where to begin, where to end, how many times to repeat How are these 3 attributes conveyed in the music notation above? How are they conveyed in the Scratch `repeat` block? In Scratch, note that the `repeat` block "envelopes" the code to be repeated. This specified both the beginning and end of the repeated code. Find and record a set of instructions containing a repetition clause (e.g., Instructions on a shampoo bottle, a recipe, etc.). How are these attributes conveyed there? If any are missing, how would the reader infer them? Ask students to present examples that they have found. Note that the instructions "Lather. Rinse. Repeat." do not contain all 3 attributes needed to convey repetition. How does a reader know where to begin, where to end, and how many times to repeat in this example? Tempo Students will utilize loops in creating audio. Direct students to Tempo. Ask a student to read the instructions aloud. Students will create a Scratch program that manipulates tempo by doing the following: Create a new program in Scratch. Copy the script directly above. Make another version where the `tempo` increases faster. Make another version where the `tempo` increases much slower. Make another version where the `tempo` starts out fast and then decreases. Make another version where the `tempo` starts out slow, then gets fast, then gets slow again. NOTE: You should make all 5 scripts within one Scratch program. Personalize it in at least 3 other ways. Regular Polygon Generator Students will create a program that generalizes loops to create regular polygons of any number of sides. Direct student to Regular Polygon Generator. Students will do the following: Draw a shape with a number of sides based upon the value of a variable named `sides`. For example, if the variable `sides` were 3, it would draw a triangle, if `sides` were 8, it would draw an octagon. Draw the shape based on the variable `size` that determines the length of each side. Make your generator unique, usable, and efficient. Personalize it in at least 3 ways. Test your program! Make sure it works correctly for an assortment of values for both `size` and `sides`. Provide documentation for your program (describe what it does) as the Instructions. Be sure to describe how your program is original. Students are given two question to think about to determine a formula for a regular polygon: You are working with two variables—what are they, and how might they be relevant? `sides` and `size`. `sides` will indicate the number of turns (repetitions in the loop) and `size` will indicate the length of each side. What numeric value would a square use to fill the blank? A triangle? Use these to think of a function to generalize them. The angle is roughly 360º / `sides`. Homework: Conditional Loops Compared Students will complete a short reading about two styles of looping. Direct student to Conditional Loops Compared. Remind students that the next class will begin with a brief discussion of the reading. ------------------------- Check-in: Conditional Loops Compared The teacher will lead a short discussion over the reading, Conditional Loops Compared. Ask students to summarize the two loops discussed in the reading. Ask students to consider the following difference between the two loop constructs—"the `repeat` block has a connector at the bottom of it, but the `forever` block does not. How does this affect their usage?" `forever` blocks cannot have follow-up code that executes once the loop ends (the condition is satisfied), because `forever` loops do not end. Repeat Until Students will trace a repeat until loop by creating a table. Note:* This is a very important formative experience. Students should practice this technique to debug loops. Direct students to Repeat Until. Demonstrate the creation of the state table in the example. Trace the values for x by simulating execution at the board. Students will create a state table that traces the values of x in the exercise. Note: Students should not be using Scratch in this activity! The idea is that they develop an intuition of variable state through practice. This is a computational thinking exercise! Draw a 'Squiral' Students will create a program that draws a square spiral. This will involve altering the variable length each pass through the loop. Students will explain their program's functionality with a short documentation write-up. Direct students to Draw a 'Squiral'. Ask a student to read the instructions out loud. Students will create a square spiral generator: Include a new variable `length`. Draw the 'squiral' below. Consider how many sides of each "square" in the squiral are equal length and when the `length` of each side changes. Personalize the program in at least 3 other ways. Provide documentation for your program (describe what it does) as the Instructions. Be sure to describe how your program is original. Note to students that the length of each side will change each time it is drawn. How will this be represented in the program? The documentation should include a description of how the program works along with details of the personalizations. Homework: Repeat After Me Again Students will take a short quiz over `repeat until`. Direct students to Repeat After Me Again. Students should complete the quiz before the following class. ------------------------- Check-in: Repeat After Me Again Students will review the short quiz Repeat After Me Again. Present the question from Repeat After Me Again to the class: Revisit the question in Repeat after me* that states: Find and record a set of instructions containing a repetition clause (e.g., Instructions on a shampoo bottle, a recipe, etc.). How are these attributes conveyed there? If any are missing, how would the reader infer them? In that context, repetition occurred a set number of times. Find another real-world set of instructions that contain a repetition clause—this time that occurs on a condition. Outline the instructions, and indicate the conditions: when does the repetition occur and when does it not? Lead a discussion over the examples students have collected. One example might read as follows, "Beat egg whites until stiff peaks form." The repetition is the act of beating the egg whites with a mixer or whisk. The condition is the appearance of stiff peaks. How many days...? Students will explore Scratch code and discuss the use of boolean operators in conditions. Direct students to discuss the code presented in How many days...? in pairs. Each student should provide an English response to the prompt, "Please explain the workings of the script below in your own words. Pay particular attention to the `or` code blocks." As a class, discuss how the code might be rewritten to just use atomic conditions, e.g., IF month = 12, rather than the `or` operator. What are the trade-offs to each approach? Loops and Variables (Students choose one of the following) The following is a mini-project, intended to be completed individually. The three options are ordered roughly according to difficulty level. Encourage students to consider this an excellent opportunity to gauge their knowledge and skills midway through the module. The basis for the programming project as well as programming assignments in future modules is assessed in the mini-projects below. Students will select one of the following options. Note that they are roughly progressive in difficulty. Option I: Draw a Picture in Scratch Option II: Electronic Keyboard Option III: Countdown with Sprites Remind students that this mini-project serves as an excellent formative assessment of their knowledge of Scratch before they begin the project. Should they have difficulties in completing one of these projects, they should request a workshop over the problematic content. Students will each be assigned a peer's project for review. Stress that the review should adhere to the appropriate rubric! Homework: Reviewing Variables Students will read Reviewing Variables and prepare for a brief discussion. Direct students to Reviewing Variables. Remind students to be prepared to discuss the content of the page during the next class session. ------------------------- Check-in: Reviewing Variables The teacher will lead a brief discussion over the content of Reviewing Variables. Lead a discussion among students addressing the following questions: What is the difference between `change` and `set`? What does the parameter (the number that goes in the slot) represent in each case? Which is relative? absolute? Why do you think stressing the difference to novice programmers such as yourselves is important? Random Students will explore the `random` block by creating a randomly moving character in Scratch. Direct students to Random. Ask a student to read the instructions aloud. Ask students to relate what the `random` block resembles in real life. Examples include, rolling a die number from 1–6, asking someone to pick a number between 1 and 10, etc. Students will create a program that moves a character randomly on the screen with the following caveats: stay within 100 pixels (in the x- and y- directions) of the center of the screen (0, 0). You can do this as follows: If the character is below the y = -100 line, they should not go any lower. If the character is above the y = 100 line, they should not go any higher. If they are to the left of the x = -100 line, they should not go any farther left. If they are to the right of the x = 100 line, they should not go any farther right. be personalized in at least 3 ways, be usable, efficient, and effective, and provide documentation (describe what it does) in the Instructions. Be sure to describe how your program is original. Rock, Paper, Scissors Students will synthesize all of the content in the module to create a "Rock, Paper, Scissors" game. Note: This is the last prescribed programming assignment in the module. Students should be able to produce quality, working programs by this point. Direct students to Rock, Paper, Scissors. Ask a student to read the instructions aloud. Demonstrate the game rules to the class by playing a best two out of three round with a student. The following chart may be helpful in determining resolutions: chart of rock, paper, scissor outcomes. Students create an original program that should: Simulate a Rock, Paper, Scissors game, include 2 contestants who choose answers randomly, include a referee who officiates automatically (based on this chart of rock, paper, scissor outcomes ) use score variables that keep track of how many times each character has won, ends when one contestant wins three rounds, be personalized in at least 3 ways, be usable, efficient, and effective, and provide documentation (describe what it does) in the Instructions. Be sure to describe how your program is original. Note that the code to resolves wins is sometimes tricky for students to correctly construct. Students will need to use nested conditionals or Boolean operators to resolve wins. Students will each be assigned a peer's project for review. Stress that the review should adhere to the appropriate rubric! Programming Practice Quiz #3 Students will gain practice and assess their learning through a final practice quiz. Direct students to Programming Practice Quiz #3. Remind students that though this quiz does not count toward the UT grade, it gives good insight into items that will be on the module exam.
Supplementary Resources	Rock, Paper, Scissors game play