Type inference in Rust - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a variable with inferred type.

Rust

let x = [1];

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

A42

B"hello"

Ctrue

Dlet

Attempts:

3 left

💡 Hint

Common Mistakes

Using a keyword like 'let' instead of a value.

Putting the value in quotes when it should be a number.

The variable x is assigned the integer 42. Rust infers its type as i32.

2fill in blank

medium

Complete the code to declare a variable with inferred string slice type.

Rust

let greeting = [1];

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

A42

B"hello"

C'c'

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using single quotes which denote a character, not a string.

Assigning a number instead of a string.

The variable greeting is assigned a string slice "hello". Rust infers its type as &str.

3fill in blank

hard

Fix the error in the code by completing the variable assignment with correct inferred type.

Rust

let is_active = [1];

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

Atrue

B1

C"true"

D't'

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string "true" instead of boolean true.

Using a number or character instead of boolean.

The variable is_active is assigned the boolean value true. Rust infers its type as bool.

4fill in blank

hard

Fill both blanks to create a vector with inferred type and print its length.

Rust

let numbers = vec![[1]];
println!("Length: {}", numbers.[2]());

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

A1, 2, 3

Blen

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using push instead of len to get length.

Not providing elements inside vec![].

The vector numbers is created with integers 1, 2, 3. Rust infers the vector type as Vec. The len() method returns the number of elements.

5fill in blank

hard

Fill all three blanks to create a hashmap with inferred types and check if a key exists.

Rust

use std::collections::HashMap;

let mut scores = HashMap::new();
scores.insert([1], [2]);
let has_key = scores.[3](&"Blue");

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

A"Blue"

B10

Ccontains_key

Dget

Attempts:

3 left

💡 Hint

Common Mistakes

Using get instead of contains_key to check existence.

Using a number as a key instead of a string.

The hashmap scores stores a key-value pair with key "Blue" and value 10. The method contains_key checks if the key exists.