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A.3 Standalone Programs

The libraries Octave itself uses can be utilized in standalone applications. These applications then have access, for example, to the array and matrix classes, as well as to all of the Octave algorithms. The following C++ program, uses class Matrix from liboctave.a or liboctave.so.

#include <iostream>
#include <octave/oct.h>

int
main (void)
{
  std::cout << "Hello Octave world!\n";

  int n = 2;
  Matrix a_matrix = Matrix (n, n);

  for (octave_idx_type i = 0; i < n; i++)
    for (octave_idx_type j = 0; j < n; j++)
      a_matrix(i,j) = (i + 1) * 10 + (j + 1);

  std::cout << a_matrix;

  return 0;
}

mkoctfile can be used to build a standalone application with a command like

$ mkoctfile --link-stand-alone standalone.cc -o standalone
$ ./standalone
Hello Octave world!
  11 12
  21 22
$

Note that the application standalone will be dynamically linked against the Octave libraries and any Octave support libraries. The above allows the Octave math libraries to be used by an application. It does not, however, allow the script files, oct-files, or builtin functions of Octave to be used by the application. To do that the Octave interpreter needs to be initialized first. An example of how to do this can then be seen in the code

#include <iostream>
#include <octave/oct.h>
#include <octave/octave.h>
#include <octave/parse.h>

int
main (void)
{
  string_vector argv (2);
  argv(0) = "embedded";
  argv(1) = "-q";

  octave_main (2, argv.c_str_vec (), 1);

  octave_idx_type n = 2;
  octave_value_list in;

  for (octave_idx_type i = 0; i < n; i++)  
    in(i) = octave_value (5 * (i + 2));
  
  octave_value_list out = feval ("gcd", in, 1);

  if (!error_state && out.length () > 0)
    std::cout << "GCD of [" 
              << in(0).int_value () 
              << ", " 
              << in(1).int_value ()
              << "] is " << out(0).int_value () 
              << std::endl;
  else
    std::cout << "invalid\n";

  return 0;
}

which, as before, is compiled and run as a standalone application with

$ mkoctfile --link-stand-alone embedded.cc -o embedded
$ ./embedded
GCD of [10, 15] is 5
$

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