concepts: add legacy_input_iterator and legacy_iterator

concepts.hpp

@@ -9,6 +9,7 @@
 #pragma once
 
 #include <type_traits>
+#include <iterator>
 #include <utility>
 
 
@@ -170,6 +171,56 @@ namespace cruft::concepts {
         { a.max_size () } -> same_as<typename T::size_type>;
         { a.empty () } -> boolean;
     };
+
+
+    template <typename T>
+    concept move_assignable =
+        requires (T a, T b)
+    {
+        { a = std::move (b) } -> same_as<T&>;
+    };
+
+
+    template <typename T>
+    concept copy_assignable =
+        move_assignable<T> &&
+        requires (T a, T b)
+    {
+        { a = b } -> same_as<T&>;
+    };
+
+
+    template <typename T>
+    concept legacy_iterator =
+        copy_constructible<T> &&
+        copy_assignable<T> &&
+        destructible<T> &&
+        swappable<T> &&
+        requires (T t)
+    {
+        typename std::iterator_traits<T>::value_type;
+        typename std::iterator_traits<T>::difference_type;
+        typename std::iterator_traits<T>::reference;
+        typename std::iterator_traits<T>::pointer;
+        typename std::iterator_traits<T>::iterator_category;
+
+        { *t };
+        { ++t } -> same_as<T&>;
+    };
+
+    template <typename T>
+    concept legacy_input_iterator =
+        legacy_iterator<T> &&
+        equality_comparable<T> &&
+        requires (T a, T b)
+    {
+        typename std::iterator_traits<T>::reference;
+        typename std::iterator_traits<T>::value_type;
+        { a != b } -> boolean;
+
+        { ++a } -> same_as<T&>;
+        { a++ };
+    };
 }