Lesson 2.1: Loops¶

Learning Objectives¶

Students will be able to…

Duration	Description
5 minutes	Welcome, attendance, bell work, announcements
15 minutes	Lecture and examples
25 minutes	Squares and Triangles Activity
10 minutes	Debrief and wrap-up

Remind students that a program can be written in many different ways that are functionally equivalent.
Ask students to speculate as to why one version of a program might be better or worse.
Possible answers: more efficient (in time or space), shorter code, more elegant/readable code.
Use this example to demonstrate unreadable code and give examples on how the repeat blocks (loops) can help make more concise scripting.
Show students the code, ask what it does, then ask if they can think of ways to improve it.
Attempt to get students to realize that the code is redundant and could be simplified if there were a way to execute a block of code more than once.

Begin with general definition: A type of block that causes other code to run multiple times in succession.
Use real life loops to introduce the concept: water cycle, eating one spoonful at a time,use a poem like “Still I Rise” by Maya Angelou or a song with a repetitive hook like “Happy” by Pharrell Williams. If you choose to use a song, you can break students into groups and have each group choose their own song. Make sure to ask students to identify a song that has a repetitive hook without explicit lyrics.
Introduce Snap! specific loops:
- Repeat block runs the body of the loop the specified number of times.
  - Number of iterations can be a value, variable, or reporter.
- Forever block runs the body of the loop nonstop until the script is ended.
- Can be stopped either by clicking the stop sign or by any version of Stop Block.
- Repeat Until runs the body of the loop until the specified condition becomes true.
- Save detailed discussion of this loop until conditionals are introduced.

Emphasize usefulness in reducing redundancy and complexity, especially for repetitive tasks.
Simple examples are here.

Direct students to complete “Squares and Triangles Redux” individually.
If available, students should use their solutions to Lab 1.3 (“Squares and Triangles and Stars, Oh My!”) as a starting point. Ensure students “Save as…” before starting on the new lab to not overwrite their original project (part 1.1).
If student solutions for Lab 1.3 are not available, or are not correct, provide a correct implementation (the solution to Lab 1.3 can be found on the TEALS Dashboard under Additional Curriculum Materials).
Encourage students to try to use as few blocks and have as little code duplication as possible to draw each shape while still creating understandable scripts. Asa reminder you may want to make the Geometry Exterior Angles Review showing various shapes and their respective angles as a reference for students through unit 2.
Once students complete part 2.1, the remaining parts should go much more quickly as they all follow the same basic pattern.

More advanced students can add additional shapes, including a five-pointed star without interior lines.
Particularly advanced students can be encouraged to build pictures by combining multiple shapes (e.g. a house built of squares of various sizes).

Lesson 2.1 Loops (TEALS Discourse account required).