[22_2] make iterator usable with range based for loop

Kernel/Containers/iterator.hpp

@@ -37,11 +37,23 @@ template <class T> class iterator_rep : public abstract_struct {
   virtual bool busy ()= 0;
 
   /**
-   * @brief Returns the next element of the iterator.
-   * @return The next element of the iterator.
+   * @brief Returns the current element of the iterator, and move the iterator
+   * forward
+   * @return The current element of the iterator.
    */
   virtual T next ()= 0;
 
+  /**
+   * @brief Returns the current element of the iterator.
+   * @return The current element of the iterator.
+   */
+  virtual T current ()= 0;
+
+  /**
+   * @brief Increase the iterator
+   */
+  virtual void increase ()= 0;
+
   /**
    * @brief Returns the number of elements remaining in the iterator.
    * @return The number of elements remaining in the iterator.
@@ -56,6 +68,15 @@ template <class T> class iterator_rep : public abstract_struct {
  */
 template <class T> struct iterator {
   ABSTRACT_TEMPLATE (iterator, T);
+  iterator<T>    begin () { return *this; };
+  std::nullptr_t end () { return nullptr; };
+  void           operator++ () { this->rep->increase (); };
+  /**
+   * @brief Returns the current element of the iterator, then move the iterator
+   * to the next element.
+   */
+  T    operator* () { return this->rep->current (); };
+  bool operator!= (std::nullptr_t) { return this->rep->busy (); }
 };
 ABSTRACT_TEMPLATE_CODE (iterator, class, T);
 

Kernel/Containers/iterator.ipp

@@ -46,6 +46,8 @@ public:
   hashset_iterator_rep<T> (hashset<T> h);
   bool busy ();
   T    next ();
+  T    current ();
+  void increase ();
 };
 
 template <class T>
@@ -78,6 +80,20 @@ hashset_iterator_rep<T>::next () {
   return x;
 }
 
+template <class T>
+T
+hashset_iterator_rep<T>::current () {
+  ASSERT (busy (), "end of iterator");
+  T x (l->item);
+  return x;
+}
+
+template <class T>
+void
+hashset_iterator_rep<T>::increase () {
+  l= l->next;
+}
+
 template <class T>
 iterator<T>
 iterate (hashset<T> h) {
@@ -97,6 +113,8 @@ public:
   hashmap_iterator_rep (hashmap<T, U> h);
   bool busy ();
   T    next ();
+  T    current ();
+  void increase ();
 };
 
 template <class T, class U>
@@ -129,6 +147,20 @@ hashmap_iterator_rep<T, U>::next () {
   return x;
 }
 
+template <class T, class U>
+T
+hashmap_iterator_rep<T, U>::current () {
+  ASSERT (busy (), "end of iterator");
+  T x (l->item.key);
+  return x;
+}
+
+template <class T, class U>
+void
+hashmap_iterator_rep<T, U>::increase () {
+  l= l->next;
+}
+
 template <class T, class U>
 iterator<T>
 iterate (hashmap<T, U> h) {

tests/Kernel/Containers/iterator_test.cpp

@@ -57,6 +57,28 @@ TEST_CASE ("iterate on hashmap") {
   CHECK_EQ (a == string ("123"), true);
 }
 
+TEST_CASE ("ranged for on hashmap") {
+  SUBCASE ("ordinary") {
+    hashmap<int, int> h;
+    h (1)= 1;
+    h (2)= 4;
+    h (3)= 6;
+    string a;
+    for (auto i : iterate (h)) {
+      a= a * as_string (i);
+    }
+    string_eq (a, "123");
+  };
+  SUBCASE ("empty") {
+    hashmap<int, int> h;
+    string            a;
+    for (auto i : iterate (h)) {
+      a= a * as_string (i);
+    }
+    string_eq (a, "");
+  };
+}
+
 TEST_CASE ("iterate on hashset") {
   hashset<int> h;
   h->insert (1);
@@ -68,4 +90,26 @@ TEST_CASE ("iterate on hashset") {
     a << as_string (it->next ());
   }
   CHECK_EQ (a == string ("123"), true);
+}
+
+TEST_CASE ("ranged for on hashset") {
+  SUBCASE ("ordinary") {
+    hashset<int> h;
+    h->insert (1);
+    h->insert (2);
+    h->insert (3);
+    string a;
+    for (auto i : iterate (h)) {
+      a << as_string (i);
+    }
+    string_eq (a, "123");
+  };
+  SUBCASE ("empty") {
+    hashset<int> h;
+    string       a;
+    for (auto i : iterate (h)) {
+      a= a * as_string (i);
+    }
+    string_eq (a, "");
+  }
 }