### Lecture 4: The design recipe

This assignment is due on Tuesday, January 16 at 11:59pm. Submit it using Handin as assignment lecture4. Your submission is only accepted if the message “Handin successful” appears.

#### 1` `The origin of parentheses

(place-image (scale 2 bicycle horizontal-position 150 (empty-scene 300 300)) |

- At the market, I bought an apple for $1 and a sandwich for $5. What is the total that I spent? The answer to this problem is (+ 1 5), so put this in your Definitions Window:
At the market, I bought an apple for $1 and a sandwich for $5. Because a sandwich is a prepared food item, it is taxed 7%. What is the total that I spent? Define a constant named part2 with your formula.

At the market, I bought a baked apple for $1 and a sandwich for $5. Because both are prepared food items, both are taxed 7%. What is the total that I spent? Define a constant named part3 with your formula.

At the restaurant, I ordered a baked apple for $1 and a sandwich for $5. Both are taxed 7%, and I also decided to pay 20% tip on the amount before tax was added. The tip is not taxed. What is the total that I spent? Define a constant named part4 with your formula.

At the restaurant, I ordered a baked apple for $1 and a sandwich for $5. Both are taxed 7%, and I also decided to pay 20% tip on the amount after tax was added. What is the total that I spent? Define a constant named part5 with your formula.

Like the last probem, but what if I rounded up the final amount to the nearest dollar (using the ceiling function)? Define a constant named part6 with your formula.

#### 2` `Designing a function with 1 input

; Exercise 3 ; 1. Data definitions ; 2. Signature, purpose, header ; 3. Function examples ; 4. Function template ; 5. Function definition ; 6. Testing

Submit your work using Handin as assignment lecture3. Be sure to submit on time. Submit early and submit often, any number of times until the deadline!

Important Note Whenever you write a function in this class, you need to follow the design recipe.

Exercise 4. Turn all your function examples from comments into automatic tests.

Keep submitting your work any number of times until the deadline. Be sure to submit on time. Watch out for submitting to the wrong assignment.

Optional: Learn more about automatic testing.

#### 3` `Designing an animation

Optional: Read Chapter 3 of the textbook.