Simple oct function

[Iago Mosqueira]

Hello,

I want to use some fortran subroutines from the GSLIB library in octave, 
and I am attempting for the first time to write a C++ wrapper. After 
reading the manual and a few other examples, I have the C++ and F77 
functions attached at the end. There is some simple clash between int 
and octave_value_list, when I do

        mkoctfile addone.cpp -o addone.oct

I get

addone.cpp: In function `class octave_value_list Faddone(const 
octave_value_list &, int)':
addone.cpp:13: `retval' cannot be used as a function
addone.cpp:13: implicit declaration of function `int addone(...)'
addone.cpp:13: warning: cannot pass objects of type `octave_value' 
through `...'
/usr/include/octave-2.1.36/octave/oct-obj.h:173: 
`octave_value_list::octave_value_list(int)' is private
addone.cpp:15: within this context

what is the problem here? I know almost nothing about C++ and F77, but 
if I could get this simple example running I would understand how to 
make the real subroutines work.

Many thanks


iago




addone.cpp

#include <octave/config.h>
#include <octave/oct.h>
#include <stdio.h>
#include <stdlib.h>

extern "C" int Addone_ (int *, int *);

DEFUN_DLD (addone, args, nargout,
  "Addone")
{
  octave_value_list retval;

  retval(0) = addone(args(0));

  return retval;
}


addone.f

subroutine addone(x,y)

integer x
integer y
y = 1 + x
return
end subroutine




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