Improved iterators5.rs explanation.

This commit is contained in:
apogeeoak 2021-04-20 18:52:10 -04:00
parent b29ea17ea9
commit 9c88ea9126
2 changed files with 37 additions and 25 deletions

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@ -1,11 +1,14 @@
// iterators5.rs
// Rustling progress is 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.
// Execute `rustlings hint iterators5` for hints.
// 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.
@ -30,12 +33,14 @@ fn count_for(map: &HashMap<String, Progress>, value: Progress) -> usize {
count
}
fn count(map: &HashMap<String, Progress>, value: Progress) -> usize {
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_stack_for(stack: &[HashMap<String, Progress>], value: Progress) -> usize {
fn count_collection_for(collection: &[HashMap<String, Progress>], value: Progress) -> usize {
let mut count = 0;
for map in stack {
for map in collection {
for val in map.values() {
if val == &value {
count += 1;
@ -45,7 +50,10 @@ fn count_stack_for(stack: &[HashMap<String, Progress>], value: Progress) -> usiz
count
}
fn count_stack(stack: &[HashMap<String, Progress>], value: Progress) -> usize {
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)]
@ -55,7 +63,7 @@ mod tests {
#[test]
fn count_complete() {
let map = get_map();
assert_eq!(3, count(&map, Progress::Complete));
assert_eq!(3, count_iterator(&map, Progress::Complete));
}
#[test]
@ -63,22 +71,25 @@ mod tests {
let map = get_map();
assert_eq!(
count_for(&map, Progress::Complete),
count(&map, Progress::Complete)
count_iterator(&map, Progress::Complete)
);
}
#[test]
fn count_stack_complete() {
let stack = get_map_stack();
assert_eq!(6, count_stack(&stack, Progress::Complete));
fn count_collection_complete() {
let collection = get_vec_map();
assert_eq!(
6,
count_collection_iterator(&collection, Progress::Complete)
);
}
#[test]
fn count_stack_equals_for() {
let stack = get_map_stack();
fn count_collection_equals_for() {
let collection = get_vec_map();
assert_eq!(
count_stack_for(&stack, Progress::Complete),
count_stack(&stack, Progress::Complete)
count_collection_for(&collection, Progress::Complete),
count_collection_iterator(&collection, Progress::Complete)
);
}
@ -96,7 +107,7 @@ mod tests {
map
}
fn get_map_stack() -> Vec<HashMap<String, Progress>> {
fn get_vec_map() -> Vec<HashMap<String, Progress>> {
use Progress::*;
let map = get_map();

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@ -694,7 +694,7 @@ Step 2 & step 2.1:
Very similar to the lines above and below. You've got this!
Step 3:
An iterator goes through all elements in a collection, but what if we've run out of
elements? What should we expect here? If you're stuck, take a look at
elements? What should we expect here? If you're stuck, take a look at
https://doc.rust-lang.org/std/iter/trait.Iterator.html for some ideas.
"""
@ -749,12 +749,13 @@ hint = """
The documentation for the std::iter::Iterator trait contains numerous methods
that would be helpful here.
Return 0 from count_stack to make the code compile in order to test count.
Return 0 from count_collection_iterator to make the code compile in order to
test count_iterator.
The stack variable in count_stack is a slice of HashMaps. It needs to be
converted into an iterator in order to use the iterator methods.
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_stack function."""
The fold method can be useful in the count_collection_iterator function."""
# THREADS