[Rust] Iter
A baisc iter:
#[test]
fn main() {
let my_fav_fruits = vec!["banana", "custard apple", "avocado", "peach", "raspberry"];
let mut my_iterable_fav_fruits = my_fav_fruits.iter();
assert_eq!(my_iterable_fav_fruits.next(), Some(&"banana"));
assert_eq!(my_iterable_fav_fruits.next(), Some(&"custard apple"));
assert_eq!(my_iterable_fav_fruits.next(), Some(&"avocado"));
assert_eq!(my_iterable_fav_fruits.next(), Some(&"peach"));
assert_eq!(my_iterable_fav_fruits.next(), Some(&"raspberry"));
assert_eq!(my_iterable_fav_fruits.next(), None);
}
Using collectto convert iter to different type
// Step 1.
// Complete the `capitalize_first` function.
// "hello" -> "Hello"
pub fn capitalize_first(input: &str) -> String {
let mut c = input.chars();
match c.next() {
None => String::new(),
Some(first) => first.to_string().to_uppercase() + c.as_str()
}
}
// Step 2.
// Apply the `capitalize_first` function to a slice of string slices.
// Return a vector of strings.
// ["hello", "world"] -> ["Hello", "World"]
pub fn capitalize_words_vector(words: &[&str]) -> Vec<String> {
words.iter().map(|x| capitalize_first(x)).collect::<Vec<String>>()
}
// Step 3.
// Apply the `capitalize_first` function again to a slice of string slices.
// Return a single string.
// ["hello", " ", "world"] -> "Hello World"
pub fn capitalize_words_string(words: &[&str]) -> String {
words.iter().map(|x| capitalize_first(x)).collect::<String>()
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_success() {
assert_eq!(capitalize_first("hello"), "Hello");
}
#[test]
fn test_empty() {
assert_eq!(capitalize_first(""), "");
}
#[test]
fn test_iterate_string_vec() {
let words = vec!["hello", "world"];
assert_eq!(capitalize_words_vector(&words), ["Hello", "World"]);
}
#[test]
fn test_iterate_into_string() {
let words = vec!["hello", " ", "world"];
assert_eq!(capitalize_words_string(&words), "Hello World");
}
}
Other example
#[derive(Debug, PartialEq, Eq)]
pub enum DivisionError {
NotDivisible(NotDivisibleError),
DivideByZero,
}
#[derive(Debug, PartialEq, Eq)]
pub struct NotDivisibleError {
dividend: i32,
divisor: i32,
}
// Calculate `a` divided by `b` if `a` is evenly divisible by `b`.
// Otherwise, return a suitable error.
pub fn divide(a: i32, b: i32) -> Result<i32, DivisionError> {
if b == 0 {
Err(DivisionError::DivideByZero)
} else if a % b == 0 {
Ok(a/b)
} else {
Err(DivisionError::NotDivisible(NotDivisibleError{dividend:a, divisor:b}))
}
}
// Complete the function and return a value of the correct type so the test
// passes.
// Desired output: Ok([1, 11, 1426, 3])
fn result_with_list() -> Result<Vec<i32>,DivisionError> {
let numbers = vec![27, 297, 38502, 81];
let division_results: Result<Vec<i32>,DivisionError> = numbers.into_iter().map(|n| divide(n, 27)).collect();
return division_results;
}
// Complete the function and return a value of the correct type so the test
// passes.
// Desired output: [Ok(1), Ok(11), Ok(1426), Ok(3)]
fn list_of_results() -> Vec<Result<i32, DivisionError>> {
let numbers = vec![27, 297, 38502, 81];
let division_results: Vec<Result<i32, DivisionError>> = numbers.into_iter().map(|n| divide(n, 27)).collect();
return division_results;
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_success() {
assert_eq!(divide(81, 9), Ok(9));
}
#[test]
fn test_not_divisible() {
assert_eq!(
divide(81, 6),
Err(DivisionError::NotDivisible(NotDivisibleError {
dividend: 81,
divisor: 6
}))
);
}
#[test]
fn test_divide_by_0() {
assert_eq!(divide(81, 0), Err(DivisionError::DivideByZero));
}
#[test]
fn test_divide_0_by_something() {
assert_eq!(divide(0, 81), Ok(0));
}
#[test]
fn test_result_with_list() {
assert_eq!(format!("{:?}", result_with_list()), "Ok([1, 11, 1426, 3])");
}
#[test]
fn test_list_of_results() {
assert_eq!(
format!("{:?}", list_of_results()),
"[Ok(1), Ok(11), Ok(1426), Ok(3)]"
);
}
}
Using range + fold
pub fn factorial(num: u64) -> u64 {
(1..=num).fold(1, |acc, v| acc * v)
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn factorial_of_0() {
assert_eq!(1, factorial(0));
}
#[test]
fn factorial_of_1() {
assert_eq!(1, factorial(1));
}
#[test]
fn factorial_of_2() {
assert_eq!(2, factorial(2));
}
#[test]
fn factorial_of_4() {
assert_eq!(24, factorial(4));
}
}
Using product() to improve
pub fn factorial(num: u64) -> u64 {
(1..=num).product()
}
Dealing with HashMap and Collection with iter
use std::collections::HashMap;
#[derive(Clone, Copy, PartialEq, Eq)]
enum Progress {
None,
Some,
Complete,
}
fn count_for(map: &HashMap<String, Progress>, value: Progress) -> usize {
let mut count = 0;
for val in map.values() {
if val == &value {
count += 1;
}
}
count
}
fn count_iterator(map: &HashMap<String, Progress>, value: Progress) -> usize {
// map is a hashmap with String keys and Progress values.
// map = { "variables1": Complete, "from_str": None, ... }
map.values()
.filter(|&progress| *progress == value)
.count()
}
fn count_collection_for(collection: &[HashMap<String, Progress>], value: Progress) -> usize {
let mut count = 0;
for map in collection {
for val in map.values() {
if val == &value {
count += 1;
}
}
}
count
}
fn count_collection_iterator(collection: &[HashMap<String, Progress>], value: Progress) -> usize {
// collection is a slice of hashmaps.
// collection = [{ "variables1": Complete, "from_str": None, ... },
// { "variables2": Complete, ... }, ... ]
collection.iter()
.flat_map(|map| map.values())
.filter(|&progress| *progress == value)
.count()
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn count_complete() {
let map = get_map();
assert_eq!(3, count_iterator(&map, Progress::Complete));
}
#[test]
fn count_some() {
let map = get_map();
assert_eq!(1, count_iterator(&map, Progress::Some));
}
#[test]
fn count_none() {
let map = get_map();
assert_eq!(2, count_iterator(&map, Progress::None));
}
#[test]
fn count_complete_equals_for() {
let map = get_map();
let progress_states = vec![Progress::Complete, Progress::Some, Progress::None];
for progress_state in progress_states {
assert_eq!(
count_for(&map, progress_state),
count_iterator(&map, progress_state)
);
}
}
#[test]
fn count_collection_complete() {
let collection = get_vec_map();
assert_eq!(
6,
count_collection_iterator(&collection, Progress::Complete)
);
}
#[test]
fn count_collection_some() {
let collection = get_vec_map();
assert_eq!(1, count_collection_iterator(&collection, Progress::Some));
}
#[test]
fn count_collection_none() {
let collection = get_vec_map();
assert_eq!(4, count_collection_iterator(&collection, Progress::None));
}
#[test]
fn count_collection_equals_for() {
let progress_states = vec![Progress::Complete, Progress::Some, Progress::None];
let collection = get_vec_map();
for progress_state in progress_states {
assert_eq!(
count_collection_for(&collection, progress_state),
count_collection_iterator(&collection, progress_state)
);
}
}
fn get_map() -> HashMap<String, Progress> {
use Progress::*;
let mut map = HashMap::new();
map.insert(String::from("variables1"), Complete);
map.insert(String::from("functions1"), Complete);
map.insert(String::from("hashmap1"), Complete);
map.insert(String::from("arc1"), Some);
map.insert(String::from("as_ref_mut"), None);
map.insert(String::from("from_str"), None);
map
}
fn get_vec_map() -> Vec<HashMap<String, Progress>> {
use Progress::*;
let map = get_map();
let mut other = HashMap::new();
other.insert(String::from("variables2"), Complete);
other.insert(String::from("functions2"), Complete);
other.insert(String::from("if1"), Complete);
other.insert(String::from("from_into"), None);
other.insert(String::from("try_from_into"), None);
vec![map, other]
}
}
