Lesson 2.03: Booleans & Expressions

Learning Objectives

Students will be able to...

• Define and identify: boolean, expression, composition, True, False
• Evaluate a boolean expression
• Compose boolean expressions using and, or, not, <, >, and ==

Materials/Preparation

• Do Now
• Lab - Can I or Can't I?
• Associated Reading - section 2.2 of Book
• Read through the do now, lesson, and lab so that you are familiar with the requirements and can assist students.

Pacing Guide

Instructor's Notes

1. Do Now
   • Project the Do Now on the board, circulate around the class to check that students are working and understand the instructions.
2. Lesson
   • After 5 minutes, ask students to recall what a boolean is and how they used booleans in Snap!
     • Ask students what values they saw in part 1 of the Do Now (answer should be True or False)
     • Boolean expression: is an expression that evaluates to either true or false.
   • Ask Students about the difference between = and ==.
     • = is for assignment of value
     • == builds a boolean expression and is a way to compare two values
   • Remind students of boolean expressions in Snap!
     • Ask the students to recall what and, or and not did.
   • Give students additional time to finish completing part 2 of the Do Now, if needed.
   • Have a student write up the expression they used to update the can_get_license code.
     • Poll students - how many boolean expressions are used? Answers here may vary depending on the students' code.
     • Define composition: Using an expression as part of a larger expression, or a statement as part of a larger statement. You can use parentheses to compose expressions as well.
   • Parentheses: In Snap! to compose many expressions they were nested together by simply putting blocks one after another. However, in Python if you want certain things to be evaluated together, use parentheses.
3. Lab
   • Evaluate expressions with and, or, and not
   • Given written out rules, students will convert them into Boolean expressions.
   • Create a large expression using variables that describes you.
4. Debrief
   • Check student progress and completion of the lab, wrap up by taking any final questions.

Accommodation/Differentiation

If students are moving quickly, use this opportunity to go over truth tables (or ask them to research De Morgan's Law)

• Convert the following SNAP Truth Table program into Python.