Range Guide

Part of the Fundamentals section of Coddy's Rust journey — lesson 65 of 75.

In this lesson we will explore more about how range works.

Basic Syntax Range:

start..end - Creates a range from start to end (exclusive)
start..=end - Creates a range from start to end (inclusive)

..end - Creates a range from 0 to end (exclusive)
..=end - Creates a range from 0 to end (inclusive)

start.. - Creates a range from start to infinity
.. - Creates a range from negative infinity to positive infinity

Reverse Range using .rev():

(0..5).rev() - 4, 3, 2, 1, 0
(0..=5).rev() - 5, 4, 3, 2, 1, 0

Step Jumps using .step_by(n):

(0..10).step_by(2) - 0, 2, 4, 6, 8
(0..10).rev().step_by(2) - 9, 7, 5, 3, 1

For example:

// Basic forward range
for i in 0..5 { }
// Values: 0, 1, 2, 3, 4

// Inclusive range
for i in 0..=5 { }
// Values: 0, 1, 2, 3, 4, 5

// Reverse range
for i in (0..5).rev() { }
// Values: 4, 3, 2, 1, 0

// Step by 2
for i in (0..10).step_by(2) { }
// Values: 0, 2, 4, 6, 8

// Combine reverse and step
for i in (0..10).rev().step_by(3) { }
// Values: 9, 6, 3, 0

Challenge

Easy

Create a program that starts with two arrays of numbers and prints the first for the first array all of the numbers in reverse in jumps of 3 through the array positions, and for the second it prints all numbers that are divisible by 4 in reverse order. Print in the following format:

Array 1: [1], [2], [3], ...
Array 2: [1], [2], [3], ...

Cheat sheet

Range syntax in Rust:

start..end - Creates a range from start to end (exclusive)
start..=end - Creates a range from start to end (inclusive)
..end - Creates a range from 0 to end (exclusive)
..=end - Creates a range from 0 to end (inclusive)
start.. - Creates a range from start to infinity
.. - Creates a range from negative infinity to positive infinity

Reverse ranges using .rev():

(0..5).rev() - 4, 3, 2, 1, 0
(0..=5).rev() - 5, 4, 3, 2, 1, 0

Step jumps using .step_by(n):

(0..10).step_by(2) - 0, 2, 4, 6, 8
(0..10).rev().step_by(2) - 9, 7, 5, 3, 1

// Basic forward range
for i in 0..5 { }
// Values: 0, 1, 2, 3, 4

// Inclusive range
for i in 0..=5 { }
// Values: 0, 1, 2, 3, 4, 5

// Reverse range
for i in (0..5).rev() { }
// Values: 4, 3, 2, 1, 0

// Step by 2
for i in (0..10).step_by(2) { }
// Values: 0, 2, 4, 6, 8

// Combine reverse and step
for i in (0..10).rev().step_by(3) { }
// Values: 9, 6, 3, 0

Try it yourself

fn main() {
    let numbers1 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26];
    let numbers2 = [17, 53, 24, 77, 84, 98, 24, 36, 89, 31, 36];
    print!("Array 1: ");
    // Write your code here
    
    println!();
    print!("Array 2: ");
    // Write your code here
}