On Fri, 1 Nov 2019, Jan Gorecki wrote:
> Dear R developers,
>
> Motivated by discussion about checking inheritance of S3 and S4
> objects (in head matrix/array topic) I would light to shed some light
> on a minor gap about that matter in R C API.
> Currently we are able to check inheritance for S3 class objects from C
> in a robust way (no allocation, thread safe). This is unfortunately
Your premise is not correct. Rf_inherits will not GC but it can
allocate and is not thread safe.
Best,
luke
> not possible for S4 classes. I would kindly request new function in R
> C api so it can be achieved for S4 classes with no risk of allocation.
> For reference mentioned functions below. Thank you.
> Jan Gorecki
>
> // S3 inheritance
> bool INHERITS(SEXP x, SEXP char_) {
> SEXP klass;
> if (isString(klass = getAttrib(x, R_ClassSymbol))) {
> for (int i=0; i<LENGTH(klass); i++) {
> if (STRING_ELT(klass, i) == char_) return true;
> }
> }
> return false;
> }
> // S4 inheritance
> bool Rinherits(SEXP x, SEXP char_) {
> SEXP vec = PROTECT(ScalarString(char_));
> SEXP call = PROTECT(lang3(sym_inherits, x, vec));
> bool ans = LOGICAL(eval(call, R_GlobalEnv))[0]==1;
> UNPROTECT(2);
> return ans;
> }
>
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> https://stat.ethz.ch/mailman/listinfo/r-devel
>
--
Luke Tierney
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa Phone: 319-335-3386
Department of Statistics and Fax: 319-335-3017
Actuarial Science
241 Schaeffer Hall email: luke-tier...@uiowa.edu
Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu
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