[R-pkg-devel] R_registerRoutines, etc.
On 23/04/2017 7:53 PM, Rolf Turner wrote:
On 24/04/17 11:36, Duncan Murdoch wrote:
On 23/04/2017 6:18 PM, Rolf Turner wrote:
On 23/04/17 23:05, Duncan Murdoch wrote:
Looks like extern void F77_NAME(mnnd)(double *, double *, int *, double *, double *); to me.
One more (I hope it's the last!) question: One of my subroutines has an argument of type *logical*. There is no logical type in C. So, since I am perforce using C-speak, I cannot change "void *" to "void logical".
For questions like this, see Writing R Extensions section 5.2. "Logical" in R is "int *" in C, and "INTEGER" in Fortran. This is important: *there is no way to pass a Fortran "LOGICAL" from R to Fortran*. The issue is that different Fortran compilers store LOGICAL in different ways. Some are equivalent to int with 0 for FALSE, all else for TRUE, but not all are. So don't rely on it. If you need to call a Fortran subroutine that takes a LOGICAL argument, you need to write another Fortran subroutine that takes an INTEGER argument. Then compute "arg NE 0" (or whatever the Fortran version is for testing not equal to zero) and pass that to the original routine.
Hoo-boy!!! Some serious code-rewriting called for! Thanks for setting me straight on this. Is it possible that R CMD check could be set up to issue an error, or at least a warning, if it finds "logical" or "as.logical" in the argument lists of calls to .Fortran()?
The problem is at the other end. Passing an R logical is fine; it just turns into an INTEGER on its way to Fortran. I doubt if it is feasible to detect the problem in Fortran, but static analysis keeps getting better, so I could be wrong now or in a while. Duncan Murdoch
Seems like it would be a Good Idea if it is indeed possible. cheers, Rolf