onto threads just finished Cow

REVISITS.md

@@ -26,6 +26,10 @@ return results to new Vec<i32> vector
 27) lifetimes1
 28) standard library types iterators2 -> VERY IMPORTANT to understand map, chain/chain::<Vec<String>>, join
 29) iterator4 to make sure you understand fold/rfold
+30) iterator5 to make sure you understand looping through hashmaps with filter, flat_map, count
+31) box.rs for smart pointer to allocate memory in recursive types
+32) arc.rs for atomic reference counters, moving ownershup to thread::spawn.
+33) rc.rs Rc::strong_count, Rc::new and Rc::clone, and drop(). Also note "In summary, if you need shared ownership in a single-threaded context, you can use Rc. If you need shared ownership across multiple threads, you should use Arc." Rc is faster and smaller than Arc
 
-clippy conversions macros standard_library_types  threads
+clippy conversions macros threads
 

exercises/standard_library_types/arc1.rs

@@ -18,19 +18,17 @@
 // where the second TODO comment is. Try not to create any copies of the `numbers` Vec!
 // Execute `rustlings hint arc1` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 #![forbid(unused_imports)] // Do not change this, (or the next) line.
 use std::sync::Arc;
 use std::thread;
 
 fn main() {
     let numbers: Vec<_> = (0..100u32).collect();
-    let shared_numbers = // TODO
+    let shared_numbers = Arc::new(numbers);
     let mut joinhandles = Vec::new();
 
     for offset in 0..8 {
-        let child_numbers = // TODO
+        let child_numbers = shared_numbers.clone();
         joinhandles.push(thread::spawn(move || {
             let sum: u32 = child_numbers.iter().filter(|n| *n % 8 == offset).sum();
             println!("Sum of offset {} is {}", offset, sum);

exercises/standard_library_types/box1.rs

@@ -16,11 +16,9 @@
 //
 // Execute `rustlings hint box1` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 #[derive(PartialEq, Debug)]
 pub enum List {
-    Cons(i32, List),
+    Cons(i32, Box<List>),
     Nil,
 }
 
@@ -33,11 +31,11 @@ fn main() {
 }
 
 pub fn create_empty_list() -> List {
-    todo!()
+    List::Nil
 }
 
 pub fn create_non_empty_list() -> List {
-    todo!()
+    List::Cons(1, Box::new(List::Nil))
 }
 
 #[cfg(test)]

exercises/standard_library_types/cow1.rs

@@ -5,7 +5,6 @@
 // It can enclose and provide immutable access to borrowed data, and clone the data lazily when mutation or ownership is required.
 // The type is designed to work with general borrowed data via the Borrow trait.
 
-// I AM NOT DONE
 
 use std::borrow::Cow;
 
@@ -42,7 +41,7 @@ fn main() {
     let mut input = Cow::from(slice);
     match abs_all(&mut input) {
         // TODO
-        Cow::Borrowed(_) => println!("I own this slice!"),
+        Cow::Owned(_) => println!("I own this slice!"),
         _ => panic!("expected borrowed value"),
     }
 }

exercises/standard_library_types/iterators5.rs

@@ -10,8 +10,6 @@
 //
 // Make the code compile and the tests pass.
 
-// I AM NOT DONE
-
 use std::collections::HashMap;
 
 #[derive(Clone, Copy, PartialEq, Eq)]
@@ -34,7 +32,7 @@ fn count_for(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, ... }
-    todo!();
+    map.iter().filter(|(key, val)| **val == value).count()
 }
 
 fn count_collection_for(collection: &[HashMap<String, Progress>], value: Progress) -> usize {
@@ -53,7 +51,7 @@ fn count_collection_iterator(collection: &[HashMap<String, Progress>], value: Pr
     // collection is a slice of hashmaps.
     // collection = [{ "variables1": Complete, "from_str": None, ... },
     //     { "variables2": Complete, ... }, ... ]
-    todo!();
+    collection.iter().flat_map(|map| map.values()).filter(|val| **val == value).count()
 }
 
 #[cfg(test)]

exercises/standard_library_types/rc1.rs

@@ -5,7 +5,6 @@
 
 // Make this code compile by using the proper Rc primitives to express that the sun has multiple owners.
 
-// I AM NOT DONE
 use std::rc::Rc;
 
 #[derive(Debug)]
@@ -54,17 +53,17 @@ fn main() {
     jupiter.details();
 
     // TODO
-    let saturn = Planet::Saturn(Rc::new(Sun {}));
+    let saturn = Planet::Saturn(Rc::clone(&sun));
     println!("reference count = {}", Rc::strong_count(&sun)); // 7 references
     saturn.details();
 
     // TODO
-    let uranus = Planet::Uranus(Rc::new(Sun {}));
+    let uranus = Planet::Uranus(Rc::clone(&sun));
     println!("reference count = {}", Rc::strong_count(&sun)); // 8 references
     uranus.details();
 
     // TODO
-    let neptune = Planet::Neptune(Rc::new(Sun {}));
+    let neptune = Planet::Neptune(Rc::clone(&sun));
     println!("reference count = {}", Rc::strong_count(&sun)); // 9 references
     neptune.details();
 
@@ -86,12 +85,15 @@ fn main() {
     println!("reference count = {}", Rc::strong_count(&sun)); // 4 references
 
     // TODO
+    drop(earth);
     println!("reference count = {}", Rc::strong_count(&sun)); // 3 references
 
     // TODO
+    drop(venus);
     println!("reference count = {}", Rc::strong_count(&sun)); // 2 references
 
     // TODO
+    drop(mercury);
     println!("reference count = {}", Rc::strong_count(&sun)); // 1 reference
 
     assert_eq!(Rc::strong_count(&sun), 1);