make AllTrueBitSetVector an infinite range

src/amdis/utility/AllTrueBitSetVector.hpp

 #pragma once
 
+#include <cstddef>
+#include <iterator>
+
 namespace AMDiS
 {
-  /// \brief Vector-like container of bools returning always true
+  /// \brief Vector-like container of bools returning always true.
+  /**
+   * Model of an infinite range of bools of value `true` with vector-like element
+   * access by `operator[]`.
+   **/
   class AllTrueBitSetVector
   {
   public:
+    using value_type = bool;
+
     struct const_iterator
     {
-      constexpr const_iterator(bool sentinel = false) noexcept : sentinel_(sentinel) {}
+      using value_type = bool;
+      using reference = bool;
+      using difference_type = std::ptrdiff_t;
+      using iterator_category = std::forward_iterator_tag;
+
       constexpr bool operator*() const noexcept { return true; }
       constexpr const_iterator& operator++() noexcept { return *this; }
       constexpr const_iterator  operator++(int) noexcept { return *this; }
 
-      /// Comparison of the iterator is always true if both are sentinel or both are const_iterator
-      friend constexpr bool operator==(const_iterator a, const_iterator b) noexcept
-      {
-        return a.sentinel_ == b.sentinel_;
-      }
-
-      bool sentinel_ = false;
+      /// Comparison of the iterator is always true
+      constexpr bool operator==(const_iterator) const noexcept { return true; }
+      constexpr bool operator!=(const_iterator) const noexcept { return false; }
     };
 
     /// Constexpr default constructor
     constexpr AllTrueBitSetVector() noexcept = default;
 
+
+  public: // element access
+
     /// Converting to true
     constexpr operator bool() const noexcept
     {
       return true;
     }
 
-    /// Access any element of the container returning always true.
+    /// Access to any element of the container returns always true.
     template <class Index>
-    constexpr const AllTrueBitSetVector& operator[](Index const& /*index*/) const noexcept
+    constexpr AllTrueBitSetVector const& at(Index const& /*index*/) const noexcept
+    {
+      return *this;
+    }
+
+    /// Access to any element of the container returns always true.
+    template <class Index>
+    constexpr AllTrueBitSetVector const& operator[](Index const& /*index*/) const noexcept
+    {
+      return *this;
+    }
+
+    /// Access the front element of the infinite range
+    constexpr AllTrueBitSetVector const& front() const noexcept
     {
       return *this;
     }
 
+
+  public: // iterators
+
     /// Return iterator that always redirects to a bool true.
-    constexpr const_iterator begin() const noexcept { return const_iterator{false}; }
-    constexpr const_iterator end() const noexcept { return const_iterator{true}; }
+    constexpr const_iterator begin() const noexcept { return const_iterator{}; }
 
     /// Return iterator that always redirects to a bool true.
-    constexpr const_iterator cbegin() const noexcept { return const_iterator{false}; }
-    constexpr const_iterator cend() const noexcept { return const_iterator{true}; }
+    constexpr const_iterator cbegin() const noexcept { return const_iterator{}; }
+
+
+  public: // capacity and modifier
 
     /// Resize does nothing
     template <class Size>
-    constexpr void resize(Size const& /*size*/) const noexcept { /* do nothing */ }
+    constexpr void resize(Size const& /*size*/) const noexcept
+    {
+      /* do nothing */
+    }
+
+    /// The container is always non-empty
+    constexpr bool empty() const noexcept
+    {
+      return false;
+    }
   };
 
 } // end namespace AMDiS

test/AllTrueBitSetVectorTest.cpp

+#include <type_traits>
+#include <amdis/utility/AllTrueBitSetVector.hpp>
+
+#include "Tests.hpp"
+
+using namespace AMDiS;
+
+int main(int argc, char** argv)
+{
+  constexpr auto bitSet = AllTrueBitSetVector{};
+
+  // The bitset is not empty
+  AMDIS_TEST(!bitSet.empty());
+
+  // All entries are true
+  std::size_t i = 0;
+  for (auto it = bitSet.begin(); i < 10; ++it, ++i)
+    AMDIS_TEST(*it);
+
+  for (i = 0; i < 10; ++i) {
+    AMDIS_TEST(bitSet[i]);
+    AMDIS_TEST(bitSet.at(i));
+  }
+
+  // The front entry is true
+  AMDIS_TEST(bitSet.front());
+
+  // resize has not effect
+  bitSet.resize(0);
+  AMDIS_TEST(!bitSet.empty());
+
+  // use bitset element as template parameter
+  auto iconst = std::integral_constant<bool, bitSet[0]>{};
+
+  return report_errors();
+}

test/CMakeLists.txt

@@ -5,6 +5,9 @@ dune_add_test(SOURCES AccessTest.cpp
 dune_add_test(SOURCES AdaptInfoTest.cpp
   LINK_LIBRARIES amdis)
 
+dune_add_test(SOURCES AllTrueBitSetVectorTest.cpp
+  LINK_LIBRARIES amdis)
+
 foreach(_GRID RANGE 7)
   dune_add_test(NAME "BackupRestoreTest_${_GRID}"
     SOURCES BackupRestoreTest.cpp