Add retreat counterpart of advance

`prior` is to `next` what `retreat` is to `advance`
nemtrif · Nov 28, 2018 · 45f6a9a · 45f6a9a
1 parent 7e51e1c
commit 45f6a9a
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diff --git a/source/utf8/checked.h b/source/utf8/checked.h
@@ -193,6 +193,13 @@ namespace utf8
             utf8::next(it, end);
     }
 
+    template <typename octet_iterator, typename distance_type>
+    void retreat (octet_iterator& it, distance_type n, octet_iterator end)
+    {
+        for (distance_type i = 0; i < n; ++i)
+            utf8::prior(it, end);
+    }
+
     template <typename octet_iterator>
     typename std::iterator_traits<octet_iterator>::difference_type
     distance (octet_iterator first, octet_iterator last)

diff --git a/source/utf8/unchecked.h b/source/utf8/unchecked.h
@@ -116,6 +116,13 @@ namespace utf8
                 utf8::unchecked::next(it);
         }
 
+        template <typename octet_iterator, typename distance_type>
+        void retreat (octet_iterator& it, distance_type n)
+        {
+            for (distance_type i = 0; i < n; ++i)
+                utf8::unchecked::prior(it);
+        }
+
         template <typename octet_iterator>
         typename std::iterator_traits<octet_iterator>::difference_type
         distance (octet_iterator first, octet_iterator last)