Basic match usage in Rust - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to match the value and print the correct message.

Rust

let number = 3;
match number {
    [1] => println!("One"),
    2 => println!("Two"),
    3 => println!("Three"),
    _ => println!("Other"),
}

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

A1

B4

C0

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using a number that does not match the arm, causing the wrong message to print.

Leaving the blank empty or with invalid syntax.

The match arm for 1 should be 1 to correctly match the value and print "One".

2fill in blank

medium

Complete the code to match a character and print the correct message.

Rust

let letter = 'b';
match letter {
    'a' => println!("A"),
    [1] => println!("B"),
    'c' => println!("C"),
    _ => println!("Other"),
}

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

A'b'

B'd'

C'e'

D'f'

Attempts:

3 left

💡 Hint

Common Mistakes

Using double quotes instead of single quotes for characters.

Choosing a character that does not match the variable.

The match arm should be 'b' to match the variable letter and print "B".

3fill in blank

hard

Fix the error in the match expression by completing the blank.

Rust

let value = 10;
match value {
    5 => println!("Five"),
    [1] => println!("Ten"),
    _ => println!("Other"),
}

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

A15

Bten

C"10"

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string "10" instead of the integer 10.

Using a variable name that is not defined.

The match arm must be 10 (an integer) to match the value variable correctly.

4fill in blank

hard

Fill both blanks to create a match that prints if a number is even or odd.

Rust

let num = 4;
match num [1] 2 {
    0 => println!("Even"),
    [2] => println!("Odd"),
}

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

A%

B==

C_

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using == instead of % for modulus.

Not using _ as a wildcard in the second match arm.

Use the modulus operator % to get the remainder and _ to match all other cases (odd numbers).

5fill in blank

hard

Fill all three blanks to match a tuple and print the correct message.

Rust

let pair = (2, 3);
match pair {
    ([1], [2]) if [3] == 2 => println!("First is two"),
    _ => println!("Other"),
}

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

Ax

By

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names in the tuple and the if guard.

Not using variables to destructure the tuple.

Use variables x and y to destructure the tuple, then check if x equals 2.

Practice

1. What does the match expression do in Rust?

easy

A. It compares a value against multiple patterns and runs matching code.

B. It creates a new variable with a fixed value.

C. It loops through a list of numbers.

D. It defines a function that returns a value.

Solution

1. Step 1: Understand the purpose of match

   The match expression compares a value against several patterns.

2. Step 2: Identify what happens on a match

   When a pattern matches, the corresponding code block runs.

3. Final Answer:

   It compares a value against multiple patterns and runs matching code. -> Option A

4. Quick Check:

   match checks patterns = C [OK]

Hint: Remember: match checks value patterns and runs matching code [OK]

Common Mistakes:

• Thinking match creates variables
• Confusing match with loops
• Believing match defines functions

2. Which of the following is the correct syntax for a match expression in Rust?

easy

A. match value { pattern : action, _ : default_action }

B. match (value) { pattern -> action, _ -> default_action }

C. match value { pattern => action, _ => default_action }

D. match value (pattern => action, _ => default_action)

Solution

1. Step 1: Recall Rust match syntax

   Rust uses curly braces with patterns and arrows: { pattern => action }.

2. Step 2: Check each option's syntax

   match value { pattern => action, _ => default_action } matches Rust syntax exactly; others use wrong symbols or parentheses.

3. Final Answer:

   match value { pattern => action, _ => default_action } -> Option C

4. Quick Check:

   Correct match syntax = A [OK]

Hint: Look for curly braces and => arrows in match syntax [OK]

Common Mistakes:

• Using parentheses instead of braces
• Using -> instead of =>
• Using colons instead of arrows

3. What is the output of this Rust code?

let number = 3;
match number {
  1 => println!("One"),
  2 => println!("Two"),
  3 => println!("Three"),
  _ => println!("Other"),
}

medium

A. One

B. Two

C. Other

D. Three

Solution

1. Step 1: Identify the matched value

   The variable number is 3.

2. Step 2: Find matching pattern in match arms

   The pattern 3 matches, so it prints "Three".

3. Final Answer:

   Three -> Option D

4. Quick Check:

   number=3 matches 3 => "Three" [OK]

Hint: Match value to pattern exactly to find output [OK]

Common Mistakes:

• Choosing default (_) arm instead of exact match
• Confusing numbers in patterns
• Ignoring the value of the variable

4. Find the error in this Rust code snippet:

let x = 5;
match x {
  1 => println!("One"),
  2 => println!("Two"),
  3 => println!("Three")
}

medium

A. Missing semicolon after println! macros

B. Missing default (_) arm to cover other values

C. Incorrect variable name in match

D. Using parentheses instead of braces in match

Solution

1. Step 1: Check match arms coverage

   The match covers only 1, 2, and 3 but variable is 5.

2. Step 2: Identify missing default arm

   Without a _ arm, the code will not compile because not all values are covered.

3. Final Answer:

   Missing default (_) arm to cover other values -> Option B

4. Quick Check:

   All values must be matched or _ arm added [OK]

Hint: Always add _ arm to cover unmatched cases [OK]

Common Mistakes:

• Assuming semicolons are required after println!
• Ignoring missing default arm errors
• Confusing variable names

5. You want to write a match expression that returns a string describing a number: "small" for 1 or 2, "medium" for 3 or 4, and "large" for any other number. Which code correctly uses match to do this?

hard

A. match num {
1 | 2 => "small",
3 | 4 => "medium",
_ => "large",
}

B. match num {
1, 2 => "small",
3, 4 => "medium",
_ => "large",
}

C. match num {
1 || 2 => "small",
3 || 4 => "medium",
_ => "large",
}

D. match num {
[1, 2] => "small",
[3, 4] => "medium",
_ => "large",
}

Solution

1. Step 1: Understand pattern alternatives in match

   Rust uses | to match multiple patterns in one arm.

2. Step 2: Check each option's pattern syntax

   match num { 1 | 2 => "small", 3 | 4 => "medium", _ => "large", } correctly uses 1 | 2 and 3 | 4. Others use invalid syntax like commas, ||, or arrays.

3. Final Answer:

   match num { 1 | 2 => "small", 3 | 4 => "medium", _ => "large", } -> Option A

4. Quick Check:

   Use | for multiple patterns in match arms [OK]

Hint: Use | to combine multiple patterns in one match arm [OK]

Common Mistakes:

• Using commas instead of | in patterns
• Using || which is logical OR, not pattern OR
• Trying to match arrays instead of values