This is one of those undocumented things (AFAIK): LENGTH applies only to 'vectors'. So don't use t and definitely don't set it for others. The macro expands to
#define LENGTH(x) (((VECSEXP) (x))->vecsxp.length) What is a vector here? Something which gets actually allocated by allocVector() AFAICS, that is an atomic or generic vector or an expression. OTOH, an EXTPTRSXP is stored in a cons cell. There is also a function length(), which is safer. On Mon, 24 Oct 2005, TB wrote: > Hi, > > I'm using R_MakeExternalPtr() to store handles to (COM) objects in a SEXP. > > The code basically is > > sexp = R_MakeExternalPtr(handle,R_NilValue,R_NilValue); > R_RegisterCFinalizerEx(...); > > After creating the sexp, LENGTH(sexp) returns some quite large integer > value. It seems like an "unitialized" value. > > Can I safely assume, that an SEXP of type EXTPTRSXP can only contain a > single pointer value It stores a pointer plus other things including a tag. > and never represent a vector (an array) of pointers? Or > should I maybe explicitly add something like > > SETLENGTH(sexp,1); > > Best wishes from sunny Austria, > > Thomas Baier > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > > -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
