[R-pkg-devel] Unable to access log operator in C

[Avraham Adler]

Thank you, Dirk.

However, I am an absolute clod.I just realized; I was passing in the
SEXP indicating whether or not to log the function as "log", so I
"overwrote" the symbol.

Excuse me while I go bang my head into the wall a few dozen times.

My apologies,

Avi

On Wed, Feb 28, 2024 at 7:14 PM Dirk Eddelbuettel <edd using debian.org> wrote:
>
>
> On 28 February 2024 at 19:05, Avraham Adler wrote:
> | I am hoping the solution to this question is simple, but I have not
> | been able to find one. I am building a routine in C to be called from
> | R. I am including Rmath.h. However, when I have a call to "log", I get
> | the error "called object 'log' is not a function or a function
> | pointer. When I "trick" it by calling log1p(x - 1), which I *know* is
> | exported from Rmath.h, it works.
> |
> | More completely, my includes are:
> | #include <R.h>
> | #include <Rmath.h>
> | #include <Rinternals.h>
> | #include <Rconfig.h>
> | #include <stdlib.h> // for NULL
> | #include <R_ext/Rdynload.h>
> |
> | The object being logged is a double, passed into C as an SEXP, call it
> | "a", which for now will always be a singleton. I initialize a pointer
> | double *pa = REAL(a). I eventually call log(pa[0]), which does not
> | compile and throws the error listed above. Switching the call to
> | log1p(pa[0] - 1.0) works and returns the proper answer.
> |
> | Even including math.h explicitly does not help, which makes sense as
> | it is included by Rmath.h.
>
> Can you show the actual line?  Worst case rename your source file to end in
> .cpp, include <cmath> and call std::log.
>
>   > Rcpp::cppFunction("double mylog(double x) { return std::log(x); }")
>   > mylog(exp(42))
>   [1] 42
>   >
>
> Dirk
>
> --
> dirk.eddelbuettel.com | @eddelbuettel | edd using debian.org