[Rd] CHAR(STRING_ELT( - OK but CHAR(asChar(STRING_ELT( - not, why?
maechler at stat.math.ethz.ch
Tue Jul 24 09:34:50 CEST 2007
>>>>> "BDR" == Prof Brian Ripley <ripley at stats.ox.ac.uk>
>>>>> on Mon, 23 Jul 2007 13:22:16 +0100 (BST) writes:
BDR> I think you are asking why calling asChar on a CHARSXP gives NA_STRING.
BDR> In particular, the calls you mention *are* perfectly OK and work as
BDR> As barely documented in R-exts, asChar is designed for vector arguments: a
BDR> CHARSXP is not a vector. It gives NA_STRING for invalid inputs.
BDR> The asXXXX family of functions are designed to coerce as necessary user
BDR> inputs, and CHARSXPs are not visible at R level.
BDR> In general, with internal functions you are expected to
BDR> read the code to find out what they do before using
BDR> There is no R '2.4', but the behaviour of asChar was the same in R 2.4.0
BDR> except for the adding of SYMSXP at
BDR> r40358 | maechler | 2007-01-04 11:07:04 +0000 (Thu, 04 Jan 2007) | 1 line
BDR> eliminate CHAR_STAR in methods/src/ as per old "todo"
BDR> which message does not help me at all. Perhaps Martin can explain?
I had to " svn diff -r40357:40358 " to see :
What I did was to basically add
else if(TYPEOF(x) == SYMSXP)
to asChar() which allowed to eliminate a macro and a similar if()
in C code from methods where there's been a long standing "TODO"
The only change this could have was to *not* return an NA
in the 'symbol/name' cases it gave NA before.
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