Library: fix a suptle misconception in the design of IterAdapter

again surprising how such fundamental bugs can hide for years...

Here the reason is that IterAdapter leaves the representation of "NIL" to
its instantiation / users; some users (here in for example the ScopedCollection)
can choose to allow for different representations of "NIL", but the comparison
provided by IterAdapter just compares the embedded pos by face value.

src/lib/iter-adapter.hpp

@@ -240,7 +240,9 @@ namespace lib {
         {
           if (check())
             iterNext (source_,pos_);                             // extension point: free function iterNext(...)
-        }
+          check();
+        }    // checkPoint() might mark end condition
+            //  for comparison with IterAdapter{}
       
       
     private:

src/lib/scoped-collection.hpp

@@ -470,8 +470,8 @@ namespace lib {
       
       
       
-      typedef IterAdapter<      I *, const ScopedCollection *> iterator;
-      typedef IterAdapter<const I *, const ScopedCollection *> const_iterator;
+      using iterator       = IterAdapter<      I *, const ScopedCollection *>;
+      using const_iterator = IterAdapter<const I *, const ScopedCollection *>;
       
       
       iterator       begin()       { return iterator       (this, _access_begin()); }

tests/library/iter-adapter-test.cpp

@@ -78,7 +78,6 @@ namespace test{
         iterator       end()         { return       iterator();                          }
         const_iterator begin() const { return const_iterator(data_.begin(),data_.end()); }
         const_iterator end()   const { return const_iterator();                          }
-        
       };
     
     
@@ -130,6 +129,8 @@ namespace test{
         iterator       end ()             { return iterator();       }
         const_iterator end ()       const { return const_iterator(); }
         
+        size_t         size()  const { return numberz_.size(); }
+        
         
         
       protected: /* ==== API for the IterAdapter ==== */
@@ -351,6 +352,36 @@ namespace test{
               
              // *iter = i+1;   ///////////TODO this should be const, but it isn't
             }
+          
+          
+          //---- verify support for C++11 element iteration
+          i = 0;
+          for (auto& elm : elms) // NOTE: TestContainer exposes pointers
+            {
+              ++elm; // can indeed modify contents
+              --elm;
+              CHECK (*elm == i);
+              ++i;
+            }
+          CHECK (size_t(i) == elms.size());
+          
+          i = 0;
+          for (auto const& elm : elms)
+            {
+              CHECK (*elm == i);
+              // ++elm; // can not modify contents
+              ++i;
+            }
+          CHECK (size_t(i) == elms.size());
+          
+          i = 0;
+          for (auto const& elm : const_elms)
+            {
+              CHECK (*elm == i);
+              // ++elm; // can not modify contents
+              ++i;
+            }
+          CHECK (size_t(i) == elms.size());
         }
       
       

tests/library/scoped-collection-test.cpp

@@ -182,6 +182,21 @@ namespace test{
               }
             
             
+            // Test c++11 foreach iteration
+            check = 0;
+            for (auto& entry : coll)
+              {
+                CHECK (check == entry.getVal());
+                ++check;
+              }
+            check = 0;
+            for (auto const& entry : const_coll)
+              {
+                CHECK (check == entry.getVal());
+                ++check;
+              }
+            
+            
             // Verify correct behaviour of iteration end
             CHECK (! (coll.end()));
             CHECK (isnil (coll.end()));