Hello,
I understand now that this is very intended after reading:
http://cran.r-project.org/doc/manuals/R-ints.html#The-CHARSXP-cache
So we are not supposed to modify a CHARSXP character by character.
Sorry for the noise.
Romain
On 03/07/2010 10:48 AM, Romain Francois wrote:
Hello,
As this little program illustrates, duplicating a STRSXP does not seem
deep enough.
require( inline )
fx <- cfunction( signature( x = "character"), '
SEXP y = PROTECT( duplicate( x ) );
int n = LENGTH(x);
int nc = 0 ;
char* p = 0 ;
for( int i=0; i<n; i++){
p = (char*)( CHAR( STRING_ELT( y , i ) ) );
nc = strlen( p ) ;
for( int j=0; j<nc; j++){
p[j] = tolower( p[j] ) ;
}
}
SEXP res = PROTECT( allocVector( VECSXP, 2 ) );
SET_VECTOR_ELT( res, 0, x );
SET_VECTOR_ELT( res, 1, y );
UNPROTECT(2) ;
return res ;
', includes = "#include <ctype.h>" )
I get :
> fx( c("Tick", "Tack", "Tock" ) )
[[1]]
[1] "tick" "tack" "tock"
[[2]]
[1] "tick" "tack" "tock"
where I would expect the second element of the list to not be modified.
Is this intended ?
If not, I can track it down to the DUPLICATE_ATOMIC_VECTOR in
duplicate.c and submit a patch.
Also, CHARSXP don't seem to be actually duplicated :
case CHARSXP:
return s;
Romain
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Romain Francois
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http://romainfrancois.blog.free.fr
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