Scalar data types in Rust - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an integer variable named num with value 10.

Rust

let num: [1] = 10;

Drag options to blanks, or click blank then click option'

Ai32

BString

Cbool

Df64

Attempts:

3 left

💡 Hint

Common Mistakes

Using String instead of an integer type.

Using bool which is for true/false values.

Using f64 which is for floating-point numbers.

The i32 type is the default integer type in Rust for 32-bit signed integers.

2fill in blank

medium

Complete the code to declare a floating-point variable named pi with value 3.14.

Rust

let pi: [1] = 3.14;

Drag options to blanks, or click blank then click option'

Abool

Bi32

Cf64

Dchar

Attempts:

3 left

💡 Hint

Common Mistakes

Using i32 which is for integers.

Using bool which is for true/false values.

Using char which is for single characters.

The f64 type is the default floating-point type in Rust for 64-bit floats.

3fill in blank

hard

Fix the error in the code by choosing the correct scalar type for the variable flag.

Rust

let flag: [1] = true;

Drag options to blanks, or click blank then click option'

Ai32

Bbool

Cf64

Dchar

Attempts:

3 left

💡 Hint

Common Mistakes

Using integer or floating types for boolean values.

Using char which is for characters.

The bool type is used for true or false values in Rust.

4fill in blank

hard

Fill both blanks to declare a character variable letter with value 'A'.

Rust

let letter: [1] = [2];

Drag options to blanks, or click blank then click option'

Achar

B'A'

C"A"

DString

Attempts:

3 left

💡 Hint

Common Mistakes

Using double quotes which create a string, not a char.

Using String type for a single character.

The char type stores a single character, which is written with single quotes like 'A'.

5fill in blank

hard

Fill all three blanks to declare a tuple data with an integer, a float, and a boolean.

Rust

let data: ([1], [2], [3]) = (42, 3.14, true);

Drag options to blanks, or click blank then click option'

Ai32

Bf64

Cbool

Dchar

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up types or using char incorrectly.

Using string types instead of scalar types.

The tuple contains an integer (i32), a floating-point number (f64), and a boolean (bool).

Practice

1. Which of the following is NOT a scalar data type in Rust?

easy

A. Integer

B. Boolean

C. Array

D. Character

Solution

1. Step 1: Recall scalar data types in Rust

   Scalar types include integers, floats, booleans, and characters, which hold a single value.

2. Step 2: Identify the non-scalar type

   An array holds multiple values and is a compound type, not scalar.

3. Final Answer:

   Array -> Option C

4. Quick Check:

   Scalar types exclude arrays [OK]

Hint: Scalar types hold one value; arrays hold many [OK]

Common Mistakes:

• Confusing arrays with scalar types
• Thinking floats are not scalar
• Mixing compound and scalar types

2. Which of the following is the correct way to declare a boolean variable named is_active set to true in Rust?

easy

A. let is_active: bool = true;

B. let is_active = True;

C. let is_active = 1;

D. let is_active: boolean = true;

Solution

1. Step 1: Check Rust boolean syntax

   Rust uses lowercase true and false for booleans, and the type is bool.

2. Step 2: Validate each option

   let is_active: bool = true; correctly declares is_active as a bool with value true. let is_active = True; uses uppercase True which is invalid. let is_active = 1; assigns an integer, not a boolean. let is_active: boolean = true; uses boolean which is not a Rust type.

3. Final Answer:

   let is_active: bool = true; -> Option A

4. Quick Check:

   Boolean type is bool and value is lowercase true [OK]

Hint: Booleans use lowercase true/false and type bool [OK]

Common Mistakes:

• Using uppercase True/False
• Using wrong type name boolean
• Assigning integers to booleans

3. What will be the output of the following Rust code?

let x: i32 = 10;
let y: f64 = 3.5;
println!("{}", x as f64 + y);

medium

A. 13

B. 13.5

C. Type error

D. 10.0

Solution

1. Step 1: Understand type casting in the code

   The integer x is cast to f64 using as f64, so 10 becomes 10.0.

2. Step 2: Perform the addition

   Adding 10.0 (casted x) and 3.5 (y) results in 13.5.

3. Final Answer:

   13.5 -> Option B

4. Quick Check:

   Cast integer to float, then add floats = 13.5 [OK]

Hint: Cast integers to float before adding floats [OK]

Common Mistakes:

• Forgetting to cast integer
• Expecting integer addition
• Assuming type error without cast

4. Identify the error in the following Rust code snippet:

let letter: char = "a";

medium

A. Missing semicolon

B. char cannot be assigned a letter

C. Variable name is invalid

D. char type must use single quotes, not double quotes

Solution

1. Step 1: Check char literal syntax

   In Rust, char literals must be enclosed in single quotes, e.g., 'a', not double quotes.

2. Step 2: Analyze the code

   The code uses double quotes "a", which is a string slice, not a char. This causes a type mismatch error.

3. Final Answer:

   char type must use single quotes, not double quotes -> Option D

4. Quick Check:

   char literals use single quotes 'a' [OK]

Hint: Use single quotes for char, double quotes for strings [OK]

Common Mistakes:

• Using double quotes for char
• Confusing char with string
• Ignoring type mismatch errors

5. You want to store the temperature reading 36.6 in Rust using scalar types. Which declaration is best and why?

Options:
A) let temp: i32 = 36.6;
B) let temp: char = '36';
C) let temp: bool = true;
D) let temp: f64 = 36.6;

hard

A. let temp: f64 = 36.6; because floats store decimal numbers

B. let temp: char = '36'; because characters store numbers

C. let temp: bool = true; because temperature is true or false

D. let temp: i32 = 36.6; because integers store decimal numbers

Solution

1. Step 1: Understand the data type needed for decimal numbers

   Temperature 36.6 has a decimal part, so it requires a floating-point type like f64.

2. Step 2: Evaluate each option

   let temp: i32 = 36.6; because integers store decimal numbers tries to assign a decimal to an integer, which is invalid. let temp: f64 = 36.6; because floats store decimal numbers correctly uses f64 for decimals. let temp: bool = true; because temperature is true or false uses boolean, which is unrelated. let temp: char = '36'; because characters store numbers uses char with invalid multi-character literal.

3. Final Answer:

   let temp: f64 = 36.6; because floats store decimal numbers -> Option A

4. Quick Check:

   Decimal numbers need float types like f64 [OK]

Hint: Use float types for decimal numbers like temperature [OK]

Common Mistakes:

• Assigning decimals to integers
• Using bool for numeric values
• Using char for multi-digit numbers