core: add function to easy expose a type

CMakeLists.txt

@@ -82,6 +82,7 @@ SET(${PROJECT_NAME}_HEADERS
   ${${PROJECT_NAME}_SOLVERS_HEADERS}
   include/eigenpy/eigenpy.hpp
   include/eigenpy/exception.hpp
+  include/eigenpy/expose.hpp
   include/eigenpy/details.hpp
   include/eigenpy/fwd.hpp
   include/eigenpy/map.hpp

include/eigenpy/expose.hpp

+/*
+ * Copyright 2019, INRIA
+ */
+
+#ifndef __eigenpy_expose_hpp__
+#define __eigenpy_expose_hpp__
+
+#include "eigenpy/registration.hpp"
+
+namespace eigenpy
+{
+  namespace internal
+  {
+    ///
+    /// \brief Allows a template specialization.
+    ///
+    template<typename T>
+    struct call_expose
+    {
+      static inline void run() { T::expose(); }
+    };
+  } // namespace internal
+  
+  ///
+  /// \brief Call the expose function of a given type T.
+  ///
+  template<typename T>
+  inline void expose()
+  {
+    if(not register_symbolic_link_to_registered_type<T>())
+      internal::call_expose<T>::run();
+  }
+}
+
+#endif // ifndef __eigenpy_expose_hpp__

include/eigenpy/fwd.hpp

@@ -26,5 +26,7 @@
   #define EIGENPY_DEFAULT_ALIGNMENT_VALUE Eigen::Unaligned
 #endif
 
+#include "eigenpy/expose.hpp"
+
 #endif // ifndef __eigenpy_fwd_hpp__