[Rd] Rf_PrintValue problem with methods::show

[Byron Ellis]

Indeed, you run into the same problem when trying to use PrintValue in
a package (say, for debugging purposes). I just have an implementation
that uses GlobalEnv instead of BaseEnv though I'm not sure that it's
necessarily the correct choice (though it has yet to do something I
don't want).

On 4/8/07, Simon Urbanek <simon.urbanek at r-project.org> wrote:
> Deepayan,
>
> don't mind my last mail - one shouldn't write e-mails before the
> first cup of coffee in the morning ;).. "methods" used to be excluded
> from the embedded startup (AFAIR), but that's no longer the case, so
> it must be something else. Sorry for the noise (I'm off to get the
> coffee :P).
>
> Cheers,
> Simon
>
> On Apr 8, 2007, at 8:31 AM, Simon Urbanek wrote:
>
> > Deepayan,
> >
> > you fail to load the methods package, so you cannot use S4. Eval
> > "library(methods)" first then everything is fine.
> >
> > Cheers,
> > Simon
> >
> > On Apr 7, 2007, at 7:33 PM, Deepayan Sarkar wrote:
> >
> >> Hi,
> >>
> >> I think this is a bug (even though I can't find documentation
> >> explicitly saying that it should work). Basically, Rf_PrintValue(obj)
> >> fails when 'obj' is an S4 object that should be printed using show()
> >> rather than print(). From the error message I'm guessing that the
> >> need
> >> to use show is detected correctly but then show is not found.
> >>
> >> "cbind2" in the code below is just a representative object, the same
> >> holds for the few other S4 objects I have tried.
> >>
> >> The following uses r-devel on i686-pc-linux-gnu, but the results are
> >> same with R 2.4.1 (with suitable changes to the R_ParseVector call).
> >> On powerpc Linux I get a segfault.
> >>
> >>
> >> $ RPROG=R-devel
> >> $ ${RPROG} --version | head -1
> >> R version 2.6.0 Under development (unstable) (2007-04-06 r41080)
> >> $ export LD_LIBRARY_PATH=`${RPROG} RHOME`/lib
> >> $ cat parseEvalS4.c
> >>
> >> #include <Rinternals.h>
> >> #include <Rembedded.h>
> >> #include <R_ext/Parse.h>
> >>
> >> int main(int argc, char *argv[])
> >> {
> >>     SEXP e, val;
> >>     int i, errorOccurred;
> >>     ParseStatus status;
> >>     char *cmds[] = { "show(5)", "show(cbind2)", "cbind2" };
> >>
> >>     argv[0] = "R";
> >>     Rf_initEmbeddedR(argc, argv);
> >>
> >>     for (i = 0; i < 3; i++) {
> >>         printf("** I **: Executing command: %s\n", cmds[i]);
> >>         PROTECT(e = R_ParseVector(mkString(cmds[i]), -1, &status,
> >> R_NilValue));
> >>         val = eval(VECTOR_ELT(e, 0), R_GlobalEnv);
> >>         printf("** I **: Evaluation succeeded, now printing using
> >> Rf_PrintValue:\n");
> >>         Rf_PrintValue(val);
> >>         UNPROTECT(1);
> >>     }
> >>
> >>     Rf_endEmbeddedR(0);
> >>     return 0;
> >> }
> >>
> >> $
> >> $ gcc -o parseEvalS4 \
> >>>        `${RPROG} CMD config --cppflags` \
> >>>        `${RPROG} CMD config --ldflags` parseEvalS4.c
> >> $
> >> $ ${RPROG} CMD ./parseEvalS4 --vanilla --silent
> >> ** I **: Executing command: show(5)
> >> [1] 5
> >> ** I **: Evaluation succeeded, now printing using Rf_PrintValue:
> >> [1] 5
> >> ** I **: Executing command: show(cbind2)
> >> standardGeneric for "cbind2" defined from package "methods"
> >>
> >> function (x, y)
> >> standardGeneric("cbind2")
> >> <environment: 0x8b34ef8>
> >> Methods may be defined for arguments: x, y
> >>
> >> ** I **: Evaluation succeeded, now printing using Rf_PrintValue:
> >> NULL
> >> ** I **: Executing command: cbind2
> >> ** I **: Evaluation succeeded, now printing using Rf_PrintValue:
> >> Error: could not find function "show"
> >> Error: unprotect(): only 0 protected items
> >> $
> >>
> >> -Deepayan
> >>
> >> ______________________________________________
> >> R-devel at r-project.org mailing list
> >> https://stat.ethz.ch/mailman/listinfo/r-devel
> >>
> >>
> >
>
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>


-- 
Byron Ellis (byron.ellis at gmail.com)
"Oook" -- The Librarian