23.conversions
as_ref_mut.rs
Github solution link
// as_ref_mut.rs
//
// AsRef and AsMut allow for cheap reference-to-reference conversions. Read more
// about them at https://doc.rust-lang.org/std/convert/trait.AsRef.html and
// https://doc.rust-lang.org/std/convert/trait.AsMut.html, respectively.
//
// Execute `rustlings hint as_ref_mut` or use the `hint` watch subcommand for a
// hint.
// I AM NOT DONE
// Obtain the number of bytes (not characters) in the given argument.
// TODO: Add the AsRef trait appropriately as a trait bound.
fn byte_counter<T: AsRef<str>>(arg: T) -> usize {
arg.as_ref().as_bytes().len()
}
// Obtain the number of characters (not bytes) in the given argument.
// TODO: Add the AsRef trait appropriately as a trait bound.
fn char_counter<T: AsRef<str>>(arg: T) -> usize {
arg.as_ref().chars().count()
}
// Squares a number using as_mut().
// TODO: Add the appropriate trait bound.
fn num_sq<T: AsMut<u32>>(arg: &mut T) {
// TODO: Implement the function body.
*arg.as_mut() = *arg.as_mut() * *arg.as_mut()
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn different_counts() {
let s = "Café au lait";
assert_ne!(char_counter(s), byte_counter(s));
}
#[test]
fn same_counts() {
let s = "Cafe au lait";
assert_eq!(char_counter(s), byte_counter(s));
}
#[test]
fn different_counts_using_string() {
let s = String::from("Café au lait");
assert_ne!(char_counter(s.clone()), byte_counter(s));
}
#[test]
fn same_counts_using_string() {
let s = String::from("Cafe au lait");
assert_eq!(char_counter(s.clone()), byte_counter(s));
}
#[test]
fn mut_box() {
let mut num: Box<u32> = Box::new(3);
num_sq(&mut num);
assert_eq!(*num, 9);
}
}
from_into.rs
Github solution link
// from_into.rs
//
// The From trait is used for value-to-value conversions. If From is implemented
// correctly for a type, the Into trait should work conversely. You can read
// more about it at https://doc.rust-lang.org/std/convert/trait.From.html
//
// Execute `rustlings hint from_into` or use the `hint` watch subcommand for a
// hint.
#[derive(Debug)]
struct Person {
name: String,
age: usize,
}
// We implement the Default trait to use it as a fallback
// when the provided string is not convertible into a Person object
impl Default for Person {
fn default() -> Person {
Person {
name: String::from("John"),
age: 30,
}
}
}
// Your task is to complete this implementation in order for the line `let p =
// Person::from("Mark,20")` to compile Please note that you'll need to parse the
// age component into a `usize` with something like `"4".parse::<usize>()`. The
// outcome of this needs to be handled appropriately.
//
// Steps:
// 1. If the length of the provided string is 0, then return the default of
// Person.
// 2. Split the given string on the commas present in it.
// 3. Extract the first element from the split operation and use it as the name.
// 4. If the name is empty, then return the default of Person.
// 5. Extract the other element from the split operation and parse it into a
// `usize` as the age.
// If while parsing the age, something goes wrong, then return the default of
// Person Otherwise, then return an instantiated Person object with the results
// I AM NOT DONE
impl From<&str> for Person {
fn from(s: &str) -> Person {
let parts: Vec<&str> = s.split(',').collect();
if parts.len() >= 2 && parts[0].len() > 0 {
let age: Result<usize, _> = parts[1].parse();
if let Ok(age) = age {
Person {
name: parts[0].into(),
age: age.into(),
}
} else {
Person::default()
}
} else {
Person::default()
}
}
}
fn main() {
// Use the `from` function
let p1 = Person::from("Mark,20");
// Since From is implemented for Person, we should be able to use Into
let p2: Person = "Gerald,70".into();
println!("{:?}", p1);
println!("{:?}", p2);
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_default() {
// Test that the default person is 30 year old John
let dp = Person::default();
assert_eq!(dp.name, "John");
assert_eq!(dp.age, 30);
}
#[test]
fn test_bad_convert() {
// Test that John is returned when bad string is provided
let p = Person::from("");
assert_eq!(p.name, "John");
assert_eq!(p.age, 30);
}
#[test]
fn test_good_convert() {
// Test that "Mark,20" works
let p = Person::from("Mark,20");
assert_eq!(p.name, "Mark");
assert_eq!(p.age, 20);
}
#[test]
fn test_bad_age() {
// Test that "Mark,twenty" will return the default person due to an
// error in parsing age
let p = Person::from("Mark,twenty");
assert_eq!(p.name, "John");
assert_eq!(p.age, 30);
}
#[test]
fn test_missing_comma_and_age() {
let p: Person = Person::from("Mark");
assert_eq!(p.name, "John");
assert_eq!(p.age, 30);
}
#[test]
fn test_missing_age() {
let p: Person = Person::from("Mark,");
assert_eq!(p.name, "John");
assert_eq!(p.age, 30);
}
#[test]
fn test_missing_name() {
let p: Person = Person::from(",1");
assert_eq!(p.name, "John");
assert_eq!(p.age, 30);
}
#[test]
fn test_missing_name_and_age() {
let p: Person = Person::from(",");
assert_eq!(p.name, "John");
assert_eq!(p.age, 30);
}
#[test]
fn test_missing_name_and_invalid_age() {
let p: Person = Person::from(",one");
assert_eq!(p.name, "John");
assert_eq!(p.age, 30);
}
#[test]
fn test_trailing_comma() {
let p: Person = Person::from("Mike,32,");
assert_eq!(p.name, "Mike");
assert_eq!(p.age, 32);
}
#[test]
fn test_trailing_comma_and_some_string() {
let p: Person = Person::from("Mike,32,man");
assert_eq!(p.name, "Mike");
assert_eq!(p.age, 32);
}
}
from_str.rs
Github solution link
// from_str.rs
//
// This is similar to from_into.rs, but this time we'll implement `FromStr` and
// return errors instead of falling back to a default value. Additionally, upon
// implementing FromStr, you can use the `parse` method on strings to generate
// an object of the implementor type. You can read more about it at
// https://doc.rust-lang.org/std/str/trait.FromStr.html
//
// Execute `rustlings hint from_str` or use the `hint` watch subcommand for a
// hint.
use std::num::ParseIntError;
use std::str::FromStr;
#[derive(Debug, PartialEq)]
struct Person {
name: String,
age: usize,
}
// We will use this error type for the `FromStr` implementation.
#[derive(Debug, PartialEq)]
enum ParsePersonError {
// Empty input string
Empty,
// Incorrect number of fields
BadLen,
// Empty name field
NoName,
// Wrapped error from parse::<usize>()
ParseInt(ParseIntError),
}
// I AM NOT DONE
// Steps:
// 1. If the length of the provided string is 0, an error should be returned
// 2. Split the given string on the commas present in it
// 3. Only 2 elements should be returned from the split, otherwise return an
// error
// 4. Extract the first element from the split operation and use it as the name
// 5. Extract the other element from the split operation and parse it into a
// `usize` as the age with something like `"4".parse::<usize>()`
// 6. If while extracting the name and the age something goes wrong, an error
// should be returned
// If everything goes well, then return a Result of a Person object
//
// As an aside: `Box<dyn Error>` implements `From<&'_ str>`. This means that if
// you want to return a string error message, you can do so via just using
// return `Err("my error message".into())`.
impl FromStr for Person {
type Err = ParsePersonError;
fn from_str(s: &str) -> Result<Person, Self::Err> {
if s.len() == 0 {
Err(ParsePersonError::Empty)
} else {
let parts: Vec<&str> = s.split(',').collect();
// println!("{} {}", s, parts.len());
if parts.len() == 2 {
let age: Result<usize, _> = parts[1].parse();
if parts[0].len() == 0 {
Err(ParsePersonError::NoName)
} else {
match age {
Ok(age) => Ok(Person {
name: parts[0].into(),
age: age.into(),
}),
Err(e) => Err(ParsePersonError::ParseInt(e)),
}
}
} else {
Err(ParsePersonError::BadLen)
}
}
}
}
fn main() {
let p = "Mark,20".parse::<Person>().unwrap();
println!("{:?}", p);
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn empty_input() {
assert_eq!("".parse::<Person>(), Err(ParsePersonError::Empty));
}
#[test]
fn good_input() {
let p = "John,32".parse::<Person>();
assert!(p.is_ok());
let p = p.unwrap();
assert_eq!(p.name, "John");
assert_eq!(p.age, 32);
}
#[test]
fn missing_age() {
assert!(matches!(
"John,".parse::<Person>(),
Err(ParsePersonError::ParseInt(_))
));
}
#[test]
fn invalid_age() {
assert!(matches!(
"John,twenty".parse::<Person>(),
Err(ParsePersonError::ParseInt(_))
));
}
#[test]
fn missing_comma_and_age() {
assert_eq!("John".parse::<Person>(), Err(ParsePersonError::BadLen));
}
#[test]
fn missing_name() {
assert_eq!(",1".parse::<Person>(), Err(ParsePersonError::NoName));
}
#[test]
fn missing_name_and_age() {
assert!(matches!(
",".parse::<Person>(),
Err(ParsePersonError::NoName | ParsePersonError::ParseInt(_))
));
}
#[test]
fn missing_name_and_invalid_age() {
assert!(matches!(
",one".parse::<Person>(),
Err(ParsePersonError::NoName | ParsePersonError::ParseInt(_))
));
}
#[test]
fn trailing_comma() {
assert_eq!("John,32,".parse::<Person>(), Err(ParsePersonError::BadLen));
}
#[test]
fn trailing_comma_and_some_string() {
assert_eq!(
"John,32,man".parse::<Person>(),
Err(ParsePersonError::BadLen)
);
}
}
try_from_into.rs
Github solution link
// try_from_into.rs
//
// TryFrom is a simple and safe type conversion that may fail in a controlled
// way under some circumstances. Basically, this is the same as From. The main
// difference is that this should return a Result type instead of the target
// type itself. You can read more about it at
// https://doc.rust-lang.org/std/convert/trait.TryFrom.html
//
// Execute `rustlings hint try_from_into` or use the `hint` watch subcommand for
// a hint.
use std::convert::{TryFrom, TryInto};
#[derive(Debug, PartialEq)]
struct Color {
red: u8,
green: u8,
blue: u8,
}
// We will use this error type for these `TryFrom` conversions.
#[derive(Debug, PartialEq)]
enum IntoColorError {
// Incorrect length of slice
BadLen,
// Integer conversion error
IntConversion,
}
// I AM NOT DONE
// Your task is to complete this implementation and return an Ok result of inner
// type Color. You need to create an implementation for a tuple of three
// integers, an array of three integers, and a slice of integers.
//
// Note that the implementation for tuple and array will be checked at compile
// time, but the slice implementation needs to check the slice length! Also note
// that correct RGB color values must be integers in the 0..=255 range.
// Tuple implementation
impl TryFrom<(i16, i16, i16)> for Color {
type Error = IntoColorError;
fn try_from(tuple: (i16, i16, i16)) -> Result<Self, Self::Error> {
match (
u8::try_from(tuple.0),
u8::try_from(tuple.1),
u8::try_from(tuple.2),
) {
(Ok(r), Ok(g), Ok(b)) => Ok(Color {
red: r,
green: g,
blue: b,
}),
_ => Err(IntoColorError::IntConversion),
}
}
}
// Array implementation
impl TryFrom<[i16; 3]> for Color {
type Error = IntoColorError;
fn try_from(arr: [i16; 3]) -> Result<Self, Self::Error> {
match (
u8::try_from(arr[0]),
u8::try_from(arr[1]),
u8::try_from(arr[2]),
) {
(Ok(r), Ok(g), Ok(b)) => Ok(Color {
red: r,
green: g,
blue: b,
}),
_ => Err(IntoColorError::IntConversion),
}
}
}
// Slice implementation
impl TryFrom<&[i16]> for Color {
type Error = IntoColorError;
fn try_from(slice: &[i16]) -> Result<Self, Self::Error> {
if slice.len() != 3 {
Err(IntoColorError::BadLen)
} else {
match (
u8::try_from(slice[0]),
u8::try_from(slice[1]),
u8::try_from(slice[2]),
) {
(Ok(r), Ok(g), Ok(b)) => Ok(Color {
red: r,
green: g,
blue: b,
}),
_ => Err(IntoColorError::IntConversion),
}
}
}
}
fn main() {
// Use the `try_from` function
let c1 = Color::try_from((183, 65, 14));
println!("{:?}", c1);
// Since TryFrom is implemented for Color, we should be able to use TryInto
let c2: Result<Color, _> = [183, 65, 14].try_into();
println!("{:?}", c2);
let v = vec![183, 65, 14];
// With slice we should use `try_from` function
let c3 = Color::try_from(&v[..]);
println!("{:?}", c3);
// or take slice within round brackets and use TryInto
let c4: Result<Color, _> = (&v[..]).try_into();
println!("{:?}", c4);
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_tuple_out_of_range_positive() {
assert_eq!(
Color::try_from((256, 1000, 10000)),
Err(IntoColorError::IntConversion)
);
}
#[test]
fn test_tuple_out_of_range_negative() {
assert_eq!(
Color::try_from((-1, -10, -256)),
Err(IntoColorError::IntConversion)
);
}
#[test]
fn test_tuple_sum() {
assert_eq!(
Color::try_from((-1, 255, 255)),
Err(IntoColorError::IntConversion)
);
}
#[test]
fn test_tuple_correct() {
let c: Result<Color, _> = (183, 65, 14).try_into();
assert!(c.is_ok());
assert_eq!(
c.unwrap(),
Color {
red: 183,
green: 65,
blue: 14
}
);
}
#[test]
fn test_array_out_of_range_positive() {
let c: Result<Color, _> = [1000, 10000, 256].try_into();
assert_eq!(c, Err(IntoColorError::IntConversion));
}
#[test]
fn test_array_out_of_range_negative() {
let c: Result<Color, _> = [-10, -256, -1].try_into();
assert_eq!(c, Err(IntoColorError::IntConversion));
}
#[test]
fn test_array_sum() {
let c: Result<Color, _> = [-1, 255, 255].try_into();
assert_eq!(c, Err(IntoColorError::IntConversion));
}
#[test]
fn test_array_correct() {
let c: Result<Color, _> = [183, 65, 14].try_into();
assert!(c.is_ok());
assert_eq!(
c.unwrap(),
Color {
red: 183,
green: 65,
blue: 14
}
);
}
#[test]
fn test_slice_out_of_range_positive() {
let arr = [10000, 256, 1000];
assert_eq!(
Color::try_from(&arr[..]),
Err(IntoColorError::IntConversion)
);
}
#[test]
fn test_slice_out_of_range_negative() {
let arr = [-256, -1, -10];
assert_eq!(
Color::try_from(&arr[..]),
Err(IntoColorError::IntConversion)
);
}
#[test]
fn test_slice_sum() {
let arr = [-1, 255, 255];
assert_eq!(
Color::try_from(&arr[..]),
Err(IntoColorError::IntConversion)
);
}
#[test]
fn test_slice_correct() {
let v = vec![183, 65, 14];
let c: Result<Color, _> = Color::try_from(&v[..]);
assert!(c.is_ok());
assert_eq!(
c.unwrap(),
Color {
red: 183,
green: 65,
blue: 14
}
);
}
#[test]
fn test_slice_excess_length() {
let v = vec![0, 0, 0, 0];
assert_eq!(Color::try_from(&v[..]), Err(IntoColorError::BadLen));
}
#[test]
fn test_slice_insufficient_length() {
let v = vec![0, 0];
assert_eq!(Color::try_from(&v[..]), Err(IntoColorError::BadLen));
}
}
using_as.rs
Github solution link
// using_as.rs
//
// Type casting in Rust is done via the usage of the `as` operator. Please note
// that the `as` operator is not only used when type casting. It also helps with
// renaming imports.
//
// The goal is to make sure that the division does not fail to compile and
// returns the proper type.
//
// Execute `rustlings hint using_as` or use the `hint` watch subcommand for a
// hint.
// I AM NOT DONE
fn average(values: &[f64]) -> f64 {
let total = values.iter().sum::<f64>();
total / values.len() as f64
}
fn main() {
let values = [3.5, 0.3, 13.0, 11.7];
println!("{}", average(&values));
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn returns_proper_type_and_value() {
assert_eq!(average(&[3.5, 0.3, 13.0, 11.7]), 7.125);
}
}