R devel - Nov 2019 - R C api for 'inherits' S3 and S4 objects

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
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;
}

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;
> }
>
> ______________________________________________
> R-devel at r-project.org mailing list
> 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-tierney at uiowa.edu
Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu

Thank you Luke.
That is why I don't use Rf_inherits but INHERITS which does not
allocate, provided in the email body.
I cannot do similarly for S4 classes, thus asking for some API for that.

On Fri, Nov 1, 2019 at 5:56 PM Tierney, Luke <luke-tierney at uiowa.edu>
wrote:
>
> 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;
> > }
> >
> > ______________________________________________
> > R-devel at r-project.org mailing list
> > 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-tierney at uiowa.edu
> Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu

If your goal is to perform multithreaded computations, why not perform
all necessary interactions with R upfront and then compute only on
primitives? It would help for us to understand your use case.

On Fri, Nov 1, 2019 at 4:26 AM Jan Gorecki <j.gorecki at wit.edu.pl>
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
> 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;
> }
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel


-- 
Michael Lawrence
Senior Scientist, Bioinformatics and Computational Biology
Genentech, A Member of the Roche Group
Office +1 (650) 225-7760
michafla at gene.com

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