ENH: add empty() member for Enum

src/OpenFOAM/primitives/enums/Enum.H

@@ -101,8 +101,11 @@ public:
 
     // Access
 
+        //- True if the enumeration list is empty.
+        inline bool empty() const noexcept;
+
         //- The number of name/value pairs for the enumeration.
-        inline label size() const;
+        inline label size() const noexcept;
 
         //- The list of enum names, in construction order. Same as toc()
         inline const List<word>& names() const;

src/OpenFOAM/primitives/enums/EnumI.H

@@ -28,7 +28,14 @@ License
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
 template<class EnumType>
-inline Foam::label Foam::Enum<EnumType>::size() const
+inline bool Foam::Enum<EnumType>::empty() const noexcept
+{
+    return keys_.empty();
+}
+
+
+template<class EnumType>
+inline Foam::label Foam::Enum<EnumType>::size() const noexcept
 {
     return keys_.size();
 }