[Rcpp-devel] idiom for creating an informative message for an exception

[Romain Francois]

Le 02/12/10 22:53, Dirk Eddelbuettel a écrit :
>
> On 2 December 2010 at 22:46, Romain Francois wrote:
> | Le 02/12/10 22:15, Douglas Bates a écrit :
> |>  In the lme4a package I mixed calls to Rf_error and throwing C++
> |>  exceptions.  This is causing problems and I plan to replace the calls
> |>  to Rf_error by exceptions so that there is a consistent approach.
> |>
> |>  Many of the calls to Rf_error take advantage of the fact the Rf_error
> |>  implicitly calls sprintf to create the error message.  Thus I have
> |>  calls like
> |>
> |>  	if (!d_x.size() == d_nrow * d_ncol)
> |>  	::Rf_error("%s: Dim = (%d, %d) is inconsistent with x.size() = %d",
> |>  		"ddenseMatrix::ddenseMatrix", d_nrow, d_ncol, d_x.size());
> |>
> |>  Is there a similar idiom for creating an exception's "what" argument?
> |>  I imagine I could add std::strings and maybe use some iostreams or
> |>  something like that ...
> |
> | Maybe you can use sprintf, e.g :
> |
> |
> | require( inline )
> | require( Rcpp )
> |
> | fx<- cxxfunction( , '
> |
> |      // replace 100 by whatever is large enough
> |      // the backslashes below are just because of R escaping
> |      std::string message( 100, \' \' ) ;
> |      sprintf( const_cast<char*>(message.data()), "%s %d", "bla bla", 2 ) ;
> |      return wrap( message ) ;
> |
> | ', plugin = "Rcpp" )
> |
> |
> | you could for example use sprintf in the body of the constructor of your
> | exception class.
>
> The problem is very similar to what logging classes do.  Maybe time to
> revisit our old and simple macros and do something better?
>
> Dirk

Yep. There are these in RcppCommon.h:

	#define RCPP_DEBUG( MSG ) Rprintf( "%s:%d %s\n" , __FILE__, __LINE__, 
MSG ) ;
	#define RCPP_DEBUG_1( fmt, MSG ) Rprintf( "%s:%d " fmt "\n" , __FILE__, 
__LINE__, MSG ) ;
	#define RCPP_DEBUG_2( fmt, M1, M2 ) Rprintf( "%s:%d" fmt "\n" , 
__FILE__, __LINE__, M1, M2 ) ;
	#define RCPP_DEBUG_3( fmt, M1, M2, M3 ) Rprintf( "%s:%d" fmt "\n" , 
__FILE__, __LINE__, M1, M2, M3) ;


Maybe that can be a starting point.


-- 
Romain Francois
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