Lesson 3.03: Return vs Print

Learning Objectives

Students will be able to...

• Define and identify: return, none, void
• Explain and demonstrate the difference between printing and returning

Materials/Preparation

• Do Now
• Lab - War (Card Game)
• Read through the do now, lesson, and lab so that you are familiar with the requirements and can assist students.
• Note that this lesson may take two days.

Pacing Guide

Instructor's Notes

1. Do Now
   • Students experiment with a function that returns a value, but they must add a print command to output that value.
2. Lesson
   • Ask students about what they think the difference between returning and printing is.
     • Get a volunteer to describe how they rewrote the code in the Do Now to get a value output.
     • Ask a student to write the code on the board.
   • Discuss the concept of the function contract again, explaining that the functions we will work with have both inputs and outputs.
   • Returning is a concept in Snap!, just with a different name: reporting.
     • 
   • If students appear to be struggling with the return vs. print concept, try this activity:
     • Introduction
       • Show code (just the deck definition, using only a single suit for simplicity.)
       • Ask students what is represented by the variable deck.
     • Play the game
       • With the students' assistance, write gimme_a_card() function to print a random card from the deck
       • Get one volunteer to play the gimme_a_card function and another to play randint.
       • Use the board to write output
       • One student from the class should "call" the function (by saying "Gimme a card!")
       • Trace through the function you wrote together. Should look something like this
       • Do this a few times
     • Change the function to return a card instead of printing it out
       • Give a deck of sorted cards to the student playing the function
       • Have another student "call" the function and trace through again as a class.
       • When you get to return let the student playing the function think for a moment about what they should do
       • If they don't figure it out, remind them that the caller of a function receives the returned value
       • Student should hand the card to the person who called them.
     • Further exploration: How would we print out the value of the card after it is returned?
     • Debrief the activity and talk about what was learned.

3. Lab

   • Given a shuffled deck list, students will create a program that plays the game 'War' with the user.

4. Debrief

   • Check student progress and completion of the lab, wrap up by taking any final questions.

Accommodation/Differentiation

As an extension activity, ask students to research the shuffle function and the functions associated with it.