Tuple structs in Rust - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of tuple struct field access

What is the output of this Rust code?

Rust

struct Color(u8, u8, u8);

fn main() {
    let black = Color(0, 0, 0);
    println!("{}", black.1);
}

A 0

B 1

C Compilation error

D Runtime panic

💡 Hint

Tuple struct fields are accessed by dot and index starting at 0.

The tuple struct Color has three fields indexed 0, 1, and 2. black.1 accesses the second field which is 0.

❓ Predict Output

intermediate

Output of tuple struct destructuring

What does this Rust program print?

Rust

struct Point(i32, i32);

fn main() {
    let p = Point(5, 10);
    let Point(x, y) = p;
    println!("{} {}", x, y);
}

A 10 5

B 5 10

C Compilation error

D Runtime panic

💡 Hint

Destructuring assigns fields in order to variables.

The tuple struct Point(5, 10) is destructured into x=5 and y=10, so it prints '5 10'.

🔧 Debug

advanced

Why does this tuple struct code fail to compile?

This Rust code does not compile. What is the cause of the error?

Rust

struct Size(u32, u32);

fn main() {
    let s = Size { 10, 20 };
    println!("{} {}", s.0, s.1);
}

A The fields 10 and 20 are not valid types for Size.

B Tuple structs require named fields to be initialized.

C The println! macro syntax is incorrect.

D Tuple structs cannot be initialized with curly braces and field values like normal structs.

💡 Hint

Tuple structs use parentheses for initialization, not curly braces.

Tuple structs are initialized with parentheses and positional values, not with curly braces and named fields.

📝 Syntax

advanced

Which option correctly defines a tuple struct?

Select the correct Rust syntax to define a tuple struct named 'Rectangle' with two i32 fields.

A struct Rectangle(i32, i32);

B struct Rectangle { i32, i32 };

C struct Rectangle(i32; i32);

D struct Rectangle(i32 i32);

💡 Hint

Tuple structs use parentheses and commas between types.

Option A uses correct tuple struct syntax with parentheses and comma-separated types.

🚀 Application

expert

How many elements does this tuple struct instance contain?

Given the tuple struct and instance below, how many elements does 'data' contain?

Rust

struct Data(i32, f64, char, bool);

fn main() {
    let data = Data(42, 3.14, 'x', true);
    // How many elements are in 'data'?
}

A 3

B 1

C 4

D Compilation error

💡 Hint

Count the number of types inside the tuple struct definition.

The tuple struct Data has four fields, so the instance 'data' contains 4 elements.

Practice

1. What is a tuple struct in Rust?

easy

A. A struct with named fields accessed by name

B. A struct with unnamed fields accessed by position

C. A function that returns a tuple

D. A tuple with named elements

Solution

1. Step 1: Understand tuple struct definition

   A tuple struct groups values like a tuple but has a name for the whole struct.

2. Step 2: Identify field access method

   Fields are unnamed and accessed by position using dot and index, unlike normal structs.

3. Final Answer:

   A struct with unnamed fields accessed by position -> Option B

4. Quick Check:

   Tuple struct = unnamed fields + named struct [OK]

Hint: Tuple structs have unnamed fields accessed by dot and index [OK]

Common Mistakes:

• Confusing tuple structs with normal structs having named fields
• Thinking tuple structs are just tuples without names
• Assuming fields are accessed by name

2. Which of the following is the correct syntax to define a tuple struct named Color with three u8 fields?

easy

A. struct Color(u8, u8, u8);

B. struct Color { u8, u8, u8 }

C. struct Color(u8 u8 u8);

D. struct Color = (u8, u8, u8);

Solution

1. Step 1: Recall tuple struct syntax

   Tuple structs use parentheses with types inside, separated by commas, no field names.

2. Step 2: Check each option

   struct Color(u8, u8, u8); matches correct syntax: struct Name(Type, Type, ...); others have wrong braces, missing commas, or wrong assignment.

3. Final Answer:

   struct Color(u8, u8, u8); -> Option A

4. Quick Check:

   Tuple struct syntax = struct Name(Type, Type, ...); [OK]

Hint: Tuple structs use parentheses with types, no field names [OK]

Common Mistakes:

• Using curly braces instead of parentheses
• Omitting commas between types
• Using equals sign instead of semicolon

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

struct Point(i32, i32);
fn main() {
    let p = Point(10, 20);
    println!("{}", p.1);
}

medium

A. 20

B. Point(10, 20)

C. 10

D. Compilation error

Solution

1. Step 1: Understand tuple struct field indexing

   Fields are accessed by position starting at 0, so p.0 is 10, p.1 is 20.

2. Step 2: Identify printed value

   The code prints p.1, which is the second field, value 20.

3. Final Answer:

   20 -> Option A

4. Quick Check:

   p.1 = 20 [OK]

Hint: Tuple struct fields start at index 0, p.1 is second field [OK]

Common Mistakes:

• Confusing field index starting at 1 instead of 0
• Expecting full struct print without Debug trait
• Assuming syntax error due to dot notation

4. Identify the error in this Rust code:

struct Size(u32, u32);
fn main() {
    let s = Size { 100, 200 };
    println!("{}", s.0);
}

medium

A. Missing semicolon after struct definition

B. Accessing field with dot notation is invalid

C. Using curly braces instead of parentheses to create tuple struct instance

D. Tuple structs cannot have u32 fields

Solution

1. Step 1: Check instance creation syntax

   Tuple struct instances must be created using parentheses, e.g., Size(100, 200), not curly braces.

2. Step 2: Verify field access and other syntax

   Accessing fields with dot and index is correct; semicolon is present; u32 fields are allowed.

3. Final Answer:

   Using curly braces instead of parentheses to create tuple struct instance -> Option C

4. Quick Check:

   Tuple struct instance = parentheses, not braces [OK]

Hint: Create tuple struct instances with parentheses, not braces [OK]

Common Mistakes:

• Using braces {} instead of parentheses () for tuple struct instances
• Thinking dot notation is invalid for tuple structs
• Assuming field types are restricted

5. Given the tuple struct struct Rectangle(u32, u32);, how can you write a function area that takes a Rectangle and returns its area (width * height)?

hard

A. fn area(r: Rectangle) -> u32 { r.0 + r.1 }

B. fn area(r: Rectangle) -> u32 { r[0] * r[1] }

C. fn area(r: Rectangle) -> u32 { r.width * r.height }

D. fn area(r: Rectangle) -> u32 { r.0 * r.1 }

Solution

1. Step 1: Access tuple struct fields by index

   Tuple struct fields are accessed by dot and index, e.g., r.0 and r.1.

2. Step 2: Calculate area correctly

   Area is width times height, so multiply r.0 and r.1.

3. Final Answer:

   fn area(r: Rectangle) -> u32 { r.0 * r.1 } -> Option D

4. Quick Check:

   Use r.0 and r.1 to multiply for area [OK]

Hint: Use dot and index to access tuple struct fields for calculations [OK]

Common Mistakes:

• Using indexing syntax like r[0] which is invalid
• Trying to access fields by name when tuple struct has none
• Adding fields instead of multiplying for area