added generic Vector ctor

Author: romainfrancois

inst/include/Rcpp/api/meat/Vector.h

@@ -30,6 +30,12 @@ namespace Rcpp{
         init() ;
     }
 
+    template <int RTYPE, template <class> class StoragePolicy>
+    template <typename U>
+    Vector<RTYPE, StoragePolicy>::Vector( const U& obj) {
+        Storage::set__( r_cast<RTYPE>( wrap(obj) ) ) ;
+    }
+        
     template <int RTYPE, template <class> class StoragePolicy>
     Vector<RTYPE, StoragePolicy>::Vector( const int& size ) {
         Storage::set__( Rf_allocVector( RTYPE, size) ) ;

inst/include/Rcpp/vector/Vector.h

@@ -73,6 +73,10 @@ class Vector :
     Vector( SEXP x ) {
         Storage::set__(x) ;
     }
+    
+    template <typename U>
+    explicit Vector( const U& obj) ;
+    
     Vector( const int& size, const stored_type& u ) {
         RCPP_DEBUG_2( "Vector<%d>( const int& size = %d, const stored_type& u )", RTYPE, size)
         Storage::set__( Rf_allocVector( RTYPE, size) ) ;