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Merge pull request rust-lang#646 from apogeeoak/iterator
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Added iterators5.rs exercise.
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shadows-withal authored Apr 21, 2021

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2 parents 2b766ef + 9c88ea9 commit 79cc657
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124 changes: 124 additions & 0 deletions exercises/standard_library_types/iterators5.rs
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// iterators5.rs

// Let's define a simple model to track Rustlings exercise progress. Progress
// will be modelled using a hash map. The name of the exercise is the key and
// the progress is the value. Two counting functions were created to count the
// number of exercises with a given progress. These counting functions use
// imperative style for loops. Recreate this counting functionality using
// iterators. Only the two iterator methods (count_iterator and
// count_collection_iterator) need to be modified.
// Execute `rustlings hint
// iterators5` for hints.
//
// Make the code compile and the tests pass.

// I AM NOT DONE

use std::collections::HashMap;

#[derive(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, ... }
}

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, ... }, ... ]
}

#[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_equals_for() {
let map = get_map();
assert_eq!(
count_for(&map, Progress::Complete),
count_iterator(&map, Progress::Complete)
);
}

#[test]
fn count_collection_complete() {
let collection = get_vec_map();
assert_eq!(
6,
count_collection_iterator(&collection, Progress::Complete)
);
}

#[test]
fn count_collection_equals_for() {
let collection = get_vec_map();
assert_eq!(
count_collection_for(&collection, Progress::Complete),
count_collection_iterator(&collection, Progress::Complete)
);
}

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]
}
}
16 changes: 16 additions & 0 deletions info.toml
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@@ -744,6 +744,22 @@ a mutable variable. Or, you might write code utilizing recursion
and a match clause. In Rust you can take another functional
approach, computing the factorial elegantly with ranges and iterators."""

[[exercises]]
name = "iterators5"
path = "exercises/standard_library_types/iterators5.rs"
mode = "test"
hint = """
The documentation for the std::iter::Iterator trait contains numerous methods
that would be helpful here.
Return 0 from count_collection_iterator to make the code compile in order to
test count_iterator.
The collection variable in count_collection_iterator is a slice of HashMaps. It
needs to be converted into an iterator in order to use the iterator methods.
The fold method can be useful in the count_collection_iterator function."""

# THREADS

[[exercises]]

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