Compound data types in Rust - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a tuple with an integer and a string.

Rust

let my_tuple = ([1], "hello");

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

A42

B3.14

Ctrue

D"world"

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string instead of an integer for the first element.

The tuple should start with an integer, so 42 is correct.

2fill in blank

medium

Complete the code to access the second element of the tuple.

Rust

let second = my_tuple.[1];

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

A2

B0

C1

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using index 2 or higher which is out of range for a two-element tuple.

Tuple elements are accessed by zero-based index, so the second element is at index 1.

3fill in blank

hard

Fix the error in the code to create an array of integers.

Rust

let numbers: [i32; 3] = [[1], 2, 3];

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

A"one"

B3.0

Ctrue

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string or float instead of an integer.

The array must contain integers, so 1 is the correct choice.

4fill in blank

hard

Fill both blanks to create a vector and add an element to it.

Rust

let mut v = Vec::new();
v.[1](10);
let first = v.[2](0);

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

Apush

Bget

Cpop

Dinsert

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop to add elements or insert without index.

Use push to add an element and get to access an element by index.

5fill in blank

hard

Fill all three blanks to create a tuple, destructure it, and print the values.

Rust

let [1] = ("Rust", 2024);
let (language, year) = [2];
println!("{} was released in {}", [3], year);

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

Ainfo

Clanguage

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names for the tuple and destructuring.

Printing the tuple variable instead of the destructured value.

We name the tuple info, destructure info, and print language.

Practice

1. Which of the following best describes a tuple in Rust?

easy

A. A named collection of fields with the same type.

B. A dynamically sized list of elements all of the same type.

C. A fixed-size collection of values of possibly different types grouped together.

D. A function that returns multiple values.

Solution

1. Step 1: Understand tuple characteristics

   Tuples group multiple values of different types into one fixed-size compound value.

2. Step 2: Compare with other options

   A dynamically sized list of elements all of the same type describes arrays/vecs. A named collection of fields describes structs. A function that returns multiple values is unrelated to tuples.

3. Final Answer:

   A fixed-size collection of values of possibly different types grouped together. -> Option C

4. Quick Check:

   Tuple = fixed-size, mixed types [OK]

Hint: Tuples hold fixed mixed types by position [OK]

Common Mistakes:

• Confusing tuples with arrays (dynamic size, same type)
• Thinking tuples have named fields like structs
• Assuming tuples can change size after creation

2. Which of the following is the correct syntax to define a tuple with an integer and a string in Rust?

easy

A. let my_tuple = [42, "hello"];

B. let my_tuple = (42, "hello");

C. let my_tuple = {42, "hello"};

D. let my_tuple = <42, "hello">;

Solution

1. Step 1: Recall tuple syntax

   Tuples use parentheses () with comma-separated values, e.g., (value1, value2).

2. Step 2: Check each option

   let my_tuple = (42, "hello"); uses parentheses correctly. let my_tuple = [42, "hello"]; uses square brackets (arrays). let my_tuple = {42, "hello"}; uses braces (blocks or structs). let my_tuple = <42, "hello">; uses angle brackets which are invalid here.

3. Final Answer:

   let my_tuple = (42, "hello"); -> Option B

4. Quick Check:

   Tuple syntax uses () [OK]

Hint: Tuples use parentheses () not brackets [] or braces {} [OK]

Common Mistakes:

• Using square brackets [] instead of parentheses ()
• Using braces {} which define blocks or structs
• Using angle brackets <> which are invalid here

3. What is the output of the following Rust code?

let person = ("Alice", 30);
println!("{} is {} years old", person.0, person.1);

medium

A. Alice is 30 years old

B. ("Alice", 30) is {} years old

C. person.0 is person.1 years old

D. Compilation error due to tuple access

Solution

1. Step 1: Understand tuple indexing

   Tuple elements are accessed by position using dot and index, e.g., person.0 is "Alice", person.1 is 30.

2. Step 2: Analyze the println! macro

   The placeholders {} are replaced by person.0 and person.1 values, printing "Alice is 30 years old".

3. Final Answer:

   Alice is 30 years old -> Option A

4. Quick Check:

   Tuple access person.0 and person.1 works [OK]

Hint: Access tuple elements by .0, .1, etc. [OK]

Common Mistakes:

• Trying to access tuple elements by name instead of position
• Confusing tuple with array indexing syntax
• Expecting tuple to print as a whole automatically

4. Identify the error in this Rust struct definition and fix it:

struct Point {
    x: i32,
    y i32,
}

medium

A. Trailing comma after last field is not allowed.

B. Struct fields cannot be integers.

C. Struct names must be lowercase.

D. Missing colon after y in struct field declaration.

Solution

1. Step 1: Check struct field syntax

   Each field must have a name, colon, and type. The field 'y i32' is missing a colon.

2. Step 2: Validate other options

   Fields can be integers (i32). Struct names are PascalCase by convention. Trailing commas are allowed in Rust structs.

3. Final Answer:

   Missing colon after y in struct field declaration. -> Option D

4. Quick Check:

   Field syntax requires colon between name and type [OK]

Hint: Struct fields need name: type syntax [OK]

Common Mistakes:

• Omitting colon between field name and type
• Thinking trailing commas are errors
• Using lowercase struct names (allowed but not idiomatic)

5. Given the struct and tuple below, which code correctly creates a struct instance from the tuple values?

struct Color {
    red: u8,
    green: u8,
    blue: u8,
}

let rgb = (255, 100, 50);

hard

A. let color = Color { red: rgb.0, green: rgb.1, blue: rgb.2 };

B. let color = Color(rgb.0, rgb.1, rgb.2);

C. let color = Color { 255, 100, 50 };

D. let color = (red: 255, green: 100, blue: 50);

Solution

1. Step 1: Understand struct initialization

   Structs with named fields require field names and values in braces, e.g., Color { red: val, green: val, blue: val }.

2. Step 2: Use tuple values correctly

   Tuple elements are accessed by position: rgb.0, rgb.1, rgb.2. let color = Color { red: rgb.0, green: rgb.1, blue: rgb.2 }; uses this correctly.

3. Step 3: Check incorrect options

   let color = Color(rgb.0, rgb.1, rgb.2); uses tuple struct syntax, but Color is not a tuple struct. let color = Color { 255, 100, 50 }; omits field names. let color = (red: 255, green: 100, blue: 50); is invalid syntax.

4. Final Answer:

   let color = Color { red: rgb.0, green: rgb.1, blue: rgb.2 }; -> Option A

5. Quick Check:

   Struct init needs field names with values [OK]

Hint: Use field names when creating structs from tuples [OK]

Common Mistakes:

• Trying to initialize struct without field names
• Using tuple struct syntax for normal structs
• Incorrect syntax for struct initialization