[Rcpp-devel] Extract a function from a list and create a call

[Romain Francois]

Le 22/03/10 14:14, Douglas Bates a écrit :
> I think the problem under Linux is extracting fam[0].  The error
> message to me indicates that even though fam is declared as a
> CharacterVector the SEXP it contains isn't a STRSXP.

This is not supposed to happen. The constructor of CharacterVector makes 
sure the SEXP is a STRSXP.

Vector( SEXP x ) : Base() {
     Base::setSEXP( r_cast<RTYPE>( x ) ) ;
}

and r_cast attempts to convert x to a STRSXP and throws otherwise.




When we do :

List ll(l) ;
CharacterVector fam = ll["family"] ;

ll["family"] makes a generic_name_proxy, we then ask to convert it to a 
CharacterVector, so the templated conversion operator is called :

template <typename T>
operator T(){
	return ::Rcpp::as<T>( get() ) ;
}

with T = CharacterVector, so then as<CharacterVector> is called, which 
eventually calls CharacterVector( SEXP) constructor, so fam should refer 
to a STRSXP.




You can do things like this to debug further.

Function str("str") ;
Rf_PrintValue( str( fam ) ) ;

to check.

or maybe even use the internal inspect:

inspect <- function(...) .Internal(inspect(...))


Function inspect("inspect") ;
Rf_PrintValue( inspect( fam ) ) ;


Romain

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Romain Francois
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