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.
I have a (very vague) understanding that in C one uses variables of int
type (taking the values 0, for FALSE, and 1, for TRUE) as logical variables.
It's really "nonzero for TRUE", hence the test above.
On that understanding I took a punt and replaced "void *" by "int *" for
the logical type variable. The package built and passed
"R CMD check --as-cran"
so it seems that this is OK. Is this the Right Thing To Do? Are there
any (obvious?) lurking perils?
Lots of lurking perils. You got lucky; don't count on it.
Duncan Murdoch
Thanks.
cheers,
Rolf
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