Exercism v3 launches on Sept 1st 2021. Learn more! 🚀🚀🚀
Avatar of Jonjump

Jonjump's solution

to Reverse String in the Rust Track

Published at Jun 04 2021 · 0 comments
Test suite

Reverse a string

For example: input: "cool" output: "looc"


Test your function on this string: uüu and see what happens. Try to write a function that properly reverses this string. Hint: grapheme clusters

To get the bonus test to run, remove the ignore flag (#[ignore]) from the last test, and execute the tests with:

$ cargo test --features grapheme

You will need to use external libraries (a crate in rust lingo) for the bonus task. A good place to look for those is crates.io, the official repository of crates.

Check the documentation for instructions on how to use external crates in your projects.

Rust Installation

Refer to the exercism help page for Rust installation and learning resources.

Writing the Code

Execute the tests with:

$ cargo test

All but the first test have been ignored. After you get the first test to pass, open the tests source file which is located in the tests directory and remove the #[ignore] flag from the next test and get the tests to pass again. Each separate test is a function with #[test] flag above it. Continue, until you pass every test.

If you wish to run all ignored tests without editing the tests source file, use:

$ cargo test -- --ignored

To run a specific test, for example some_test, you can use:

$ cargo test some_test

If the specific test is ignored use:

$ cargo test some_test -- --ignored

To learn more about Rust tests refer to the online test documentation

Make sure to read the Modules chapter if you haven't already, it will help you with organizing your files.

Further improvements

After you have solved the exercise, please consider using the additional utilities, described in the installation guide, to further refine your final solution.

To format your solution, inside the solution directory use

cargo fmt

To see, if your solution contains some common ineffective use cases, inside the solution directory use

cargo clippy --all-targets

Submitting the solution

Generally you should submit all files in which you implemented your solution (src/lib.rs in most cases). If you are using any external crates, please consider submitting the Cargo.toml file. This will make the review process faster and clearer.

Feedback, Issues, Pull Requests

The exercism/rust repository on GitHub is the home for all of the Rust exercises. If you have feedback about an exercise, or want to help implement new exercises, head over there and create an issue. Members of the rust track team are happy to help!

If you want to know more about Exercism, take a look at the contribution guide.


Introductory challenge to reverse an input string https://medium.freecodecamp.org/how-to-reverse-a-string-in-javascript-in-3-different-ways-75e4763c68cb

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.


//! Tests for reverse-string
//! Generated by [script][script] using [canonical data][canonical-data]
//! [script]: https://github.com/exercism/rust/blob/b829ce2/bin/init_exercise.py
//! [canonical-data]: https://raw.githubusercontent.com/exercism/problem-specifications/main/exercises/reverse-string/canonical_data.json

use reverse_string::*;

/// Process a single test case for the property `reverse`
fn process_reverse_case(input: &str, expected: &str) {
    assert_eq!(&reverse(input), expected)

/// empty string
fn test_an_empty_string() {
    process_reverse_case("", "");

/// a word
fn test_a_word() {
    process_reverse_case("robot", "tobor");

/// a capitalized word
fn test_a_capitalized_word() {
    process_reverse_case("Ramen", "nemaR");

/// a sentence with punctuation
fn test_a_sentence_with_punctuation() {
    process_reverse_case("I'm hungry!", "!yrgnuh m'I");

/// a palindrome
fn test_a_palindrome() {
    process_reverse_case("racecar", "racecar");

/// an even-sized word
fn test_an_even_sized_word() {
    process_reverse_case("drawer", "reward");

/// wide characters
fn test_wide_characters() {
    process_reverse_case("子猫", "猫子");

#[cfg(feature = "grapheme")]
/// grapheme clusters
fn test_grapheme_clusters() {
    process_reverse_case("uüu", "uüu");
pub fn reverse(input: &str) -> String {

Community comments

Find this solution interesting? Ask the author a question to learn more.

What can you learn from this solution?

A huge amount can be learned from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

  • What compromises have been made?
  • Are there new concepts here that you could read more about to improve your understanding?