Merge pull request #646 from apogeeoak/iterator

Added iterators5.rs exercise.

Author: manyinsects

exercises/standard_library_types/iterators5.rs

@@ -0,0 +1,124 @@
+// 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]
+    }
+}

info.toml

@@ -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]]