Using libRmath.a in Fortran?

G?ran Brostr?m <gb at stat.umu.se> writes:

Is it possible to call the routines in the standalone library
libRmath from Fortran programs? I'm using g77 on Linux.

Not directly. Look at e.g.

double dweibull(double x, double shape, double scale, int give_log)

this uses call-by-value semantics, where Fortran always uses
call-by-reference, i.e. pointers. So, notwithstanding linker and
symbol naming issues, you would at the very least have to write
wrapper functions to the tune of

double dweibw(double *x, double *shape, double *scale, int *give_log)
{
        return dweibull(*x, *shape, *scale, *give_log);
}

Thanks to Peter, and also to Douglas Bates, who also gave hints to
how to solve the above-mentioned "naming issues": I came up with
the following program, which (seems to!?) work:

Fortran program (nrand.f) :
---------------------------
      program nrand

      implicit none

      integer first, second
      double precision frnorm, mean, sd, y

      first = 19609
      second = 10198

      call fsetseed(first, second)

      mean = 0.d0
      sd = 1.d0

      y = frnorm(mean, sd)
      write(*, '(/3(a, f6.3))') 'rnorm(', mean, ', ', sd, ') = ', y
C     Just to show that "y is random":
      y = frnorm(mean, sd)
      write(*, '(a, 9x, f6.3/)') 'another value: ', y

      end

And the  C  wrapper (frnorm.c) :
--------------------
#define MATHLIB_STANDALONE
#include <Rmath.h>      /* to define rnorm, etc */
#include <R_ext/RS.h>   /* to define F77_NAME */

double F77_NAME(frnorm)(double *mean, double *sd)
{
  return rnorm(*mean, *sd);
}

void F77_NAME(fsetseed)(int* one, int* two)
{
  set_seed( (unsigned int)(*one), (unsigned int)(*two) );
}

And the Makefile:
-----------------
OBJS = frnorm.o nrand.o

CFLAGS = -Wall -g -I/usr/local/lib/R/include
FFLAGS = -Wall -g -C

LIBS = -lRmath

nrand: $(OBJS)
	g77 -o nrand $(OBJS) $(LIBS)

%.o : %.f
	g77 $(FFLAGS) -c $<

%.o : %.c
	gcc $(CFLAGS) -c $<
--------------------------------------------------------------------

Is this correct? And is this a correct way of accessing the random
number generator? It is the line "A little care is needed to use the
random-number routines..." from the documentation that worries me a
little.

Thanks,

G?ran

G?ran Brostr?m                      tel: +46 90 786 5223
 professor                           fax: +46 90 786 6614
 Department of Statistics            http://www.stat.umu.se/egna/gb/
 Ume? University
 SE-90187 Ume?, Sweden             e-mail: gb at stat.umu.se

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