> I'd like to ask you a question about c (macros):
> In Rinternals.h are defined:
> a) SEXP Rf_protect(SEXP);
> b) #define protect Rf_protect
> c) #define PROTECT(s) protect(s)
> As far as I understand the calls Rf_protect( x ), protect( x ) and
> PROTECT( x ) are all equalent.
> So whats the reason that there are 2 macros defined? Why 3 times the
> same when 1 distinct function would be enough?
History. People do not like writing 'Rf_protect', so PROTECT is used
instead. And the code is written as 'protect' for the same reason, and to
allow future changes under the skin. (Several macros are in fact used
differently inside R, and Rinternals.h was an attempt to extract a
reasonable subset of the internal code, not an ab initio design).