独立程序(GNU Octave(版本9.4.0))

A.3独立程序¶

Octave自己使用的库可以在独立的应用程序中使用。例如,这些应用程序可以访问数组和矩阵类,以及所有Octave算法。以下C++程序使用类Matrixliboctave.a或liboctave.so.

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

int
main ()
{
  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可以用来构建一个独立的应用程序,命令如下

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

请注意,应用程序standalone将针对Octave库和任何Octave支持库动态链接。以上内容允许应用程序使用Octave数学库。但是,它不允许应用程序使用Octave的脚本文件、oct文件或内置函数。为此,需要首先初始化Octave解释器。然后可以在代码中看到如何做到这一点的示例

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

int
main ()
{
  // Create interpreter.

  octave::interpreter interpreter;

  try
    {
      // Inhibit reading history file by calling
      //
      //   interpreter.initialize_history (false);

      // Set custom load path here if you wish by calling
      //
      //   interpreter.initialize_load_path (false);

      // Perform final initialization of interpreter, including
      // executing commands from startup files by calling
      //
      //   interpreter.initialize ();
      //
      //   if (! interpreter.is_initialized ())
      //     {
      //       std::cerr << "Octave interpreter initialization failed!"
      //                 << std::endl;
      //       exit (1);
      //     }
      //
      // You may skip this step if you don't need to do anything
      // between reading the startup files and telling the interpreter
      // that you are ready to execute commands.

      // Tell the interpreter that we're ready to execute commands:

      int status = interpreter.execute ();

      if (status != 0)
        {
          std::cerr << "creating embedded Octave interpreter failed!"
                    << std::endl;
          return status;
        }

      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 = octave::feval ("gcd", in, 1);

      if (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";
    }
  catch (const octave::exit_exception& ex)
    {
      std::cerr << "Octave interpreter exited with status = "
                << ex.exit_status () << std::endl;
    }
  catch (const octave::execution_exception&)
    {
      std::cerr << "error encountered in Octave evaluator!" << std::endl;
    }

  return 0;
}

和以前一样,它是作为一个独立的应用程序编译和运行的

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

值得重申的是,如果只从C++独立程序中调用内置函数,则不需要初始化解释器。一般规则是,对于名为function_name在解释器中,将有一个名为的C++函数Ffunction_name(注意准备资本F)可在C++API中访问。所有内置函数的语句都收集在头文件中builtin-defun-decls.h。应小心使用此函数,因为内置函数列表可能会发生变化。不能保证当前是内置函数的函数不会实现为.mfileor作为未来的动态链接函数。在代码中可以看到如何从C++调用内置函数的示例

#include <iostream>
#include <octave/oct.h>
#include <octave/builtin-defun-decls.h>

int
main ()
{
  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 << "This is a matrix:" << std::endl
            << a_matrix            << std::endl;

  octave_value_list in;
  in(0) = a_matrix;

  octave_value_list out = Fnorm (in, 1);
  double norm_of_the_matrix = out(0).double_value ();

  std::cout << "This is the norm of the matrix:" << std::endl
            << norm_of_the_matrix                << std::endl;

  return 0;
}

它作为一个独立的应用程序进行编译和运行

$ mkoctfile --link-stand-alone standalonebuiltin.cc -o standalonebuiltin
$ ./standalonebuiltin
This is a matrix:
 11 12
 21 22

This is the norm of the matrix:
34.4952
$