removed into_group_map_by_fold maybe for next.

added documentation for into_group_map_by, added into_group_map_by in the itertools trait.

Author: Sagebati

src/group_map.rs

@@ -3,16 +3,16 @@
 use std::collections::HashMap;
 use std::hash::Hash;
 use std::iter::Iterator;
-use alloc::Vec;
+use HashMapIntoIter;
 
 /// Return a `HashMap` of keys mapped to a list of their corresponding values.
 ///
 /// See [`.into_group_map()`](../trait.Itertools.html#method.into_group_map)
 /// for more information.
 pub fn into_group_map<I, K, V>(iter: I) -> HashMap<K, Vec<V>>
-where
-    I: Iterator<Item = (K, V)>,
-    K: Hash + Eq,
+    where
+        I: Iterator<Item=(K, V)>,
+        K: Hash + Eq,
 {
     let mut lookup = HashMap::new();
 
@@ -23,10 +23,10 @@ where
     lookup
 }
 
-pub fn into_group_map_by<I, K, V>(iter: I, f: impl Fn(&V) -> K) -> HashMap<K, Vec<V>>
-where
-    I: Iterator<Item = V>,
-    K: Hash + Eq,
+pub fn into_group_map_by<I, K, V>(iter: I, f: impl Fn(&V) -> K) ->HashMapIntoIter<K,Vec<V>>
+    where
+        I: Iterator<Item=V>,
+        K: Hash + Eq,
 {
     let mut lookup = HashMap::new();
 
@@ -35,29 +35,6 @@ where
         lookup.entry(key).or_insert(Vec::new()).push(val);
     }
 
-    lookup
+    lookup.into_iter()
 }
 
-pub fn into_group_map_by_fold<I, K, V, Acc, Fold>(
-    iter: impl Iterator<Item=V>,
-    f_key: impl Fn(&V) -> K,
-    init: Acc,
-    fold: Fold,
-) -> HashMap<K, Acc>
-where
-    K: Hash + Eq,
-    Acc: Clone,
-    Fold: FnMut(Acc, V) -> Acc + Clone,
-{
-    let mut lookup = HashMap::new();
-
-    for val in iter {
-        let key = f_key(&val);
-        lookup.entry(key).or_insert(Vec::new()).push(val);
-    }
-
-    lookup
-        .into_iter()
-        .map(move |(key, value)| (key, value.into_iter().fold(init.clone(), fold.clone())))
-        .collect()
-}