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The libraries Octave uses itself 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 built-in 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> #include <octave/interpreter.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 (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"; clean_up_and_exit (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 $

It is worth re-iterating that, if only built-in functions are to be called from
a C++ standalone program then it does not need to initialize the interpreter.
The general rule is that for a built-in function named `function_name`

in
the interpreter, there will be a C++ function named `Ffunction_name`

(note
the prepended capital `F`

) accessible in the C++ API. The declarations
for all built-in functions are collected in the header file
`builtin-defun-decls.h`

. This feature should be used with care as the
list of built-in functions can change. No guarantees can be made that a
function that is currently a built-in won’t be implemented as a .m file or as a
dynamically linked function in the future. An example of how to call built-in
functions from C++ can be seen in the code

#include <iostream> #include <octave/oct.h> #include <octave/builtin-defun-decls.h> int main (void) { 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; }

which is compiled and run as a standalone application with

$ 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 $

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