Example interfacing with C and arrays in Ada

whatev.ads

with Interfaces.C;

package Whatev is
   package C renames Interfaces.C;
   
   type Vector_Index is (X, Y, Z, W);
   type Vector is array (Vector_Index range <>) of aliased C.double;
   pragma Convention (C, Vector);

   procedure Vertex (Value : Vector);
   pragma Import (Convention => StdCall, Entity => Vertex,
                  External_Name => "glVertex4dv");
                  
end Whatev;