---
title: Drill 6 Solution
tags: Drills-F20, 2020
---

# Drill 6 Solution

## Question 1
Fill in the blanks in the following lambda expression. The lambda should take two Numbers as inputs and return a Number that's the product of the two input Numbers.

<a>(<b>): x * y <c>

a: ____

b: ____

c: ____

::: spoiler Answer

a: `lam`

b: `x, y` or `y, x`

c: `end`

:::

## Question 2

Can all lambda expressions be rewritten as functions?

( ) Yes
( ) No

::: spoiler Answer

(X) Yes
( ) No

You can think of lambda expressions as short-hand for one-line functions.

:::

## Question 3

What will happen if we write the following in the definitions window and then click 'Run'?

Try to answer without using Pyret.

num = 5
square = lam(n): n * n end
square(num)

( ) 25 will be output in the interactions window
( ) Nothing
( ) "The declaration of the identifier named num shadows a previous declaration of an identifier also named num"
( ) Error: "The identifier 'num' is unbound"
( ) Error: "The declaration of the identifier named square shadows a previous declaration of an identifier also named square"

::: spoiler Answer

(X) 25 will be output in the interactions window
( ) Nothing
( ) "The declaration of the identifier named num shadows a previous declaration of an identifier also named num"
( ) Error: "The identifier 'num' is unbound"
( ) Error: "The declaration of the identifier named square shadows a previous declaration of an identifier also named square"

Since `square(num)` is 25.

:::

## Question 4

What concept from this week of class is *least clear* to you?