Function parameters in Rust - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a function that takes one parameter named name.

Rust

fn greet([1]: &str) {
    println!("Hello, {}!", name);
}

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

Amessage

Bage

Cname

Dinput

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different parameter name than the one used inside the function.

Forgetting to specify the parameter type.

The function parameter must be named name to match the usage inside the function.

2fill in blank

medium

Complete the function signature to accept two parameters: a and b, both integers.

Rust

fn add([1]: i32, b: i32) -> i32 {
    a + b
}

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

Ax

Ba

Cnum

Dval

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different name than a for the first parameter.

Not matching parameter names with the function body.

The first parameter must be named a to match the function body where a + b is returned.

3fill in blank

hard

Fix the error in the function parameter to accept a string slice named text.

Rust

fn print_text([1]) {
    println!("{}", text);
}

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

Atext: &str

Btext

Ctxt

Dmessage

Attempts:

3 left

💡 Hint

Common Mistakes

Using String instead of &str when the function expects a string slice.

Not naming the parameter text.

The function expects a string slice &str named text, not an owned String.

4fill in blank

hard

Fill both blanks to define a function that takes two parameters: width and height, both unsigned integers.

Rust

fn area([1]: u32, [2]: u32) -> u32 {
    width * height
}

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

Awidth

Blength

Cheight

Ddepth

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect parameter names that don't match the function body.

Mixing up parameter names and types.

The parameters must be named width and height to match the function body.

5fill in blank

hard

Fill all three blanks to define a function that takes a string slice name, an integer age, and a boolean is_student.

Rust

fn describe_person([1]: &str, [2]: i32, [3]: bool) {
    println!("Name: {}, Age: {}, Student: {}", name, age, is_student);
}

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

Aname

Bage

Cis_student

Dstatus

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong parameter names that don't match the print statement.

Mixing up parameter types and names.

The parameters must be named name, age, and is_student to match the function body.

Practice

1. What is the purpose of function parameters in Rust?

easy

A. To send data into functions so they can use it

B. To define the return type of a function

C. To declare variables inside a function

D. To create loops inside functions

Solution

1. Step 1: Understand what parameters do

   Parameters allow functions to receive input data when called.

2. Step 2: Identify the correct purpose

   Sending data into functions makes them flexible and reusable.

3. Final Answer:

   To send data into functions so they can use it -> Option A

4. Quick Check:

   Function parameters = input data [OK]

Hint: Parameters pass data into functions for flexibility [OK]

Common Mistakes:

• Confusing parameters with return types
• Thinking parameters declare variables inside functions
• Mixing parameters with control flow like loops

2. Which of the following is the correct way to declare a function with one parameter named num of type i32 in Rust?

easy

A. fn example(num) -> i32 {}

B. fn example(i32 num) {}

C. fn example(num: i32) {}

D. fn example(num: int) {}

Solution

1. Step 1: Recall Rust function parameter syntax

   Parameters are declared as name: type, e.g., num: i32.

2. Step 2: Check each option

   fn example(num: i32) {} matches correct syntax. fn example(i32 num) {} reverses order. fn example(num) -> i32 {} misses type. fn example(num: int) {} uses wrong type name.

3. Final Answer:

   fn example(num: i32) {} -> Option C

4. Quick Check:

   Parameter syntax = name: type [OK]

Hint: Use name: type for parameters in Rust functions [OK]

Common Mistakes:

• Swapping type and name order
• Omitting the parameter type
• Using incorrect type names like 'int'

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

fn greet(name: &str) {
    println!("Hello, {}!", name);
}

fn main() {
    greet("Alice");
}

medium

A. Hello, Alice!

B. Hello, name!

C. Hello, &str!

D. Compilation error

Solution

1. Step 1: Understand the function call and parameter

   The function greet takes a string slice &str and prints a greeting with the given name.

2. Step 2: Trace the function call in main

   Calling greet("Alice") passes "Alice" as the parameter, so it prints "Hello, Alice!".

3. Final Answer:

   Hello, Alice! -> Option A

4. Quick Check:

   Function prints greeting with passed name [OK]

Hint: Parameters replace placeholders in print statements [OK]

Common Mistakes:

• Printing the parameter name instead of its value
• Confusing &str with variable name
• Expecting a compilation error due to &str

4. Identify the error in this Rust function declaration:

fn add(a i32, b: i32) -> i32 {
    a + b
}

medium

A. Parameters should be declared as 'i32 a' and 'i32 b'

B. Missing return type declaration

C. Function body missing braces

D. Missing colon between parameter name and type for 'a'

Solution

1. Step 1: Check parameter syntax

   Each parameter must have a colon between name and type, e.g., a: i32.

2. Step 2: Identify the error

   Parameter a i32 is missing the colon, causing a syntax error.

3. Final Answer:

   Missing colon between parameter name and type for 'a' -> Option D

4. Quick Check:

   Parameter syntax requires colon [OK]

Hint: Always put colon between parameter name and type [OK]

Common Mistakes:

• Omitting colon between name and type
• Confusing parameter order syntax
• Forgetting return type after ->

5. Given this function:

fn calculate_area(width: f64, height: f64) -> f64 {
    width * height
}

Which call correctly uses the function parameters to calculate the area of a 5.0 by 3.0 rectangle?

hard

A. calculate_area(5, 3)

B. calculate_area(5.0, 3.0)

C. calculate_area("5", "3")

D. calculate_area(width=5.0, height=3.0)

Solution

1. Step 1: Check parameter types

   The function expects two f64 (floating-point) parameters.

2. Step 2: Evaluate each call

   calculate_area(5, 3) uses integer literals, which Rust automatically coerces to f64 (implicit conversion). calculate_area(5.0, 3.0) uses floating-point literals matching the f64 parameter type exactly. calculate_area("5", "3") uses strings, type mismatch. calculate_area(width=5.0, height=3.0) uses named arguments, which Rust does not support.

3. Final Answer:

   calculate_area(5.0, 3.0) -> Option B

4. Quick Check:

   Use correct types and order for parameters [OK]

Hint: Match argument types exactly to parameter types [OK]

Common Mistakes:

• Using integers instead of floats without suffix
• Passing strings instead of numbers
• Trying named arguments (not supported in Rust)