Add a comment for rationale.

3 files changed, 5 insertions, 0 deletions

diff --git a/vespalib/src/vespa/vespalib/stllike/hash_map.h b/vespalib/src/vespa/vespalib/stllike/hash_map.h
index f00b7ec224d..f2431a73f28 100644
--- a/vespalib/src/vespa/vespalib/stllike/hash_map.h
+++ b/vespalib/src/vespa/vespalib/stllike/hash_map.h
@@ -38,6 +38,8 @@ public:
     insert_result insert(const value_type & value) { return _ht.insert(value); }
     template <typename InputIt>
     void insert(InputIt first, InputIt last);
+
+    /// This gives faster iteration than can be achieved by the iterators.
     template <typename Func>
     void for_each(Func func) const { _ht.for_each(func); }
     const V & operator [] (const K & key) const { return _ht.find(key)->second; }
diff --git a/vespalib/src/vespa/vespalib/stllike/hash_set.h b/vespalib/src/vespa/vespalib/stllike/hash_set.h
index a8d855d5ddd..bb16932a990 100644
--- a/vespalib/src/vespa/vespalib/stllike/hash_set.h
+++ b/vespalib/src/vespa/vespalib/stllike/hash_set.h
@@ -43,6 +43,7 @@ public:
     iterator find(const K & key)             { return _ht.find(key); }
     const_iterator find(const K & key) const { return _ht.find(key); }
 
+    /// This gives faster iteration than can be achieved by the iterators.
     template <typename Func>
     void for_each(Func func) const { _ht.for_each(func); }
 
diff --git a/vespalib/src/vespa/vespalib/stllike/hashtable.h b/vespalib/src/vespa/vespalib/stllike/hashtable.h
index 41781e649f3..16d9cde1f78 100644
--- a/vespalib/src/vespa/vespalib/stllike/hashtable.h
+++ b/vespalib/src/vespa/vespalib/stllike/hashtable.h
@@ -249,6 +249,8 @@ public:
     insert_result insert(V && node) {
         return insertInternal(std::forward<V>(node));
     }
+    
+    /// This gives faster iteration than can be achieved by the iterators.
     template <typename Func>
     void for_each(Func func) const;