add 2015 01 and 02

lib/include/aocpp/Counter.hpp

@@ -8,7 +8,7 @@ struct Counter
 {
   using difference_type = std::ptrdiff_t;
 
-  struct EmptyRef {
+  struct NoOpReference {
     template <typename T>
     auto operator=(T&&) const -> void {}
   };
@@ -31,14 +31,14 @@ struct Counter
     return n++;
   }
 
-  auto operator*() const -> EmptyRef
+  auto operator*() const -> NoOpReference
   {
     return {};
   }
 
   auto operator-(Counter rhs) const -> difference_type
   {
-    return static_cast<difference_type>(n) - static_cast<difference_type>(rhs);
+    return static_cast<difference_type>(n) - static_cast<difference_type>(rhs.n);
   }
 
   operator std::size_t() const

lib/include/aocpp/Parsing.hpp

@@ -48,4 +48,4 @@ auto ParseGrammar_(G const& grammar, std::istream & in) -> typename G::start_typ
 
 }
 
-#endif
+#endif