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<span id="Getting-Started-with-Oct_002dFiles"></span><div class="header">
<p>
Next: <a href="Matrices-and-Arrays-in-Oct_002dFiles.html" accesskey="n" rel="next">Matrices and Arrays in Oct-Files</a>, Up: <a href="Oct_002dFiles.html" accesskey="u" rel="up">Oct-Files</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<span id="Getting-Started-with-Oct_002dFiles-1"></span><h4 class="subsection">A.1.1 Getting Started with Oct-Files</h4>
<p>Oct-files are pieces of C++ code that have been compiled with the Octave API
into a dynamically loadable object. They take their name from the file which
contains the object which has the extension <samp>.oct</samp>.
</p>
<p>Finding a C++ compiler, using the correct switches, adding the right include
paths for header files, etc. is a difficult task. Octave automates this by
providing the <code>mkoctfile</code> command with which to build oct-files. The
command is available from within Octave or at the shell command line.
</p>
<span id="XREFmkoctfile"></span><dl>
<dt id="index-mkoctfile-1">: <em></em> <strong>mkoctfile</strong> <em>[-options] file …</em></dt>
<dt id="index-mkoctfile-2">: <em>[<var>output</var>, <var>status</var>] =</em> <strong>mkoctfile</strong> <em>(…)</em></dt>
<dd>
<p>The <code>mkoctfile</code> function compiles source code written in C, C++, or
Fortran. Depending on the options used with <code>mkoctfile</code>, the
compiled code can be called within Octave or can be used as a stand-alone
application.
</p>
<p><code>mkoctfile</code> can be called from the shell prompt or from the Octave
prompt. Calling it from the Octave prompt simply delegates the call to
the shell prompt. Any output is stored in the <var>output</var> variable and
the exit status in the <var>status</var> variable. If called with no outputs
and the compilation fails then Octave will emit an error. If the programmer
requests <var>output</var> or <var>status</var>, however, Octave will merely issue
a warning and it is the programmer’s responsibility to verify the command
was successful.
</p>
<p><code>mkoctfile</code> accepts the following options, all of which are optional
except for the filename of the code you wish to compile:
</p>
<dl compact="compact">
<dt>‘<samp>-I DIR</samp>’</dt>
<dd><p>Add the include directory DIR to compile commands.
</p>
</dd>
<dt>‘<samp>-D DEF</samp>’</dt>
<dd><p>Add the definition DEF to the compiler call.
</p>
</dd>
<dt>‘<samp>-l LIB</samp>’</dt>
<dd><p>Add the library LIB to the link command.
</p>
</dd>
<dt>‘<samp>-L DIR</samp>’</dt>
<dd><p>Add the library directory DIR to the link command.
</p>
</dd>
<dt>‘<samp>-M</samp>’</dt>
<dt>‘<samp>--depend</samp>’</dt>
<dd><p>Generate dependency files (.d) for C and C++ source files.
</p>
</dd>
<dt>‘<samp>-R DIR</samp>’</dt>
<dd><p>Add the run-time path to the link command.
</p>
</dd>
<dt>‘<samp>-Wl,…</samp>’</dt>
<dd><p>Pass options to the linker like "-Wl,-rpath=…".
The quotes are needed since commas are interpreted as command
separators.
</p>
</dd>
<dt>‘<samp>-W…</samp>’</dt>
<dd><p>Pass options to the assembler like "-Wa,OPTION".
</p>
</dd>
<dt>‘<samp>-c</samp>’</dt>
<dd><p>Compile but do not link.
</p>
</dd>
<dt>‘<samp>-g</samp>’</dt>
<dd><p>Enable debugging options for compilers.
</p>
</dd>
<dt>‘<samp>-o FILE</samp>’</dt>
<dt>‘<samp>--output FILE</samp>’</dt>
<dd><p>Output filename. Default extension is <samp>.oct</samp> (or <samp>.mex</samp> if
‘<samp>--mex</samp>’ is specified) unless linking a stand-alone executable.
</p>
</dd>
<dt>‘<samp>-p VAR</samp>’</dt>
<dt>‘<samp>--print VAR</samp>’</dt>
<dd><p>Print configuration variable VAR. There are three categories of
variables:
</p>
<p>Octave configuration variables that users may override with environment
variables. These are used in commands that <code>mkoctfile</code> executes.
</p>
<div class="example">
<pre class="example"> ALL_CFLAGS INCLUDEDIR
ALL_CXXFLAGS LAPACK_LIBS
ALL_FFLAGS LDFLAGS
ALL_LDFLAGS LD_STATIC_FLAG
BLAS_LIBS LFLAGS
CC LIBDIR
CFLAGS LIBOCTAVE
CPICFLAG LIBOCTINTERP
CPPFLAGS OCTAVE_LINK_OPTS
CXX OCTINCLUDEDIR
CXXFLAGS OCTAVE_LIBS
CXXLD OCTAVE_LINK_DEPS
CXXPICFLAG OCTLIBDIR
DL_LDFLAGS OCT_LINK_DEPS
F77 OCT_LINK_OPTS
F77_INTEGER8_FLAG RDYNAMIC_FLAG
FFLAGS SPECIAL_MATH_LIB
FPICFLAG XTRA_CFLAGS
INCFLAGS XTRA_CXXFLAGS
</pre></div>
<p>Octave configuration variables as above, but currently unused by
<code>mkoctfile</code>.
</p>
<div class="example">
<pre class="example"> AR
DEPEND_EXTRA_SED_PATTERN
DEPEND_FLAGS
FFTW3F_LDFLAGS
FFTW3F_LIBS
FFTW3_LDFLAGS
FFTW3_LIBS
FFTW_LIBS
FLIBS
LIBS
RANLIB
READLINE_LIBS
</pre></div>
<p>Octave configuration variables that are provided for informational
purposes only. Except for ‘<samp>OCTAVE_HOME</samp>’ and ‘<samp>OCTAVE_EXEC_HOME</samp>’,
users may not override these variables.
</p>
<p>If <code><span class="nolinebreak">OCTAVE_HOME</span></code><!-- /@w --> or <code><span class="nolinebreak">OCTAVE_EXEC_HOME</span></code><!-- /@w --> are set in the
environment, then other variables are adjusted accordingly with
<code><span class="nolinebreak">OCTAVE_HOME</span></code><!-- /@w --> or <code><span class="nolinebreak">OCTAVE_EXEC_HOME</span></code><!-- /@w --> substituted for the
original value of the directory specified by the <samp>--prefix</samp> or
<samp>--exec-prefix</samp> options that were used when Octave was configured.
</p>
<div class="example">
<pre class="example"> API_VERSION LOCALFCNFILEDIR
ARCHLIBDIR LOCALOCTFILEDIR
BINDIR LOCALSTARTUPFILEDIR
CANONICAL_HOST_TYPE LOCALVERARCHLIBDIR
DATADIR LOCALVERFCNFILEDIR
DATAROOTDIR LOCALVEROCTFILEDIR
DEFAULT_PAGER MAN1DIR
EXEC_PREFIX MAN1EXT
EXEEXT MANDIR
FCNFILEDIR OCTAVE_EXEC_HOME
IMAGEDIR OCTAVE_HOME
INFODIR OCTAVE_VERSION
INFOFILE OCTDATADIR
LIBEXECDIR OCTDOCDIR
LOCALAPIARCHLIBDIR OCTFILEDIR
LOCALAPIFCNFILEDIR OCTFONTSDIR
LOCALAPIOCTFILEDIR STARTUPFILEDIR
LOCALARCHLIBDIR
</pre></div>
</dd>
<dt>‘<samp>--link-stand-alone</samp>’</dt>
<dd><p>Link a stand-alone executable file.
</p>
</dd>
<dt>‘<samp>--mex</samp>’</dt>
<dd><p>Assume creation of a MEX file. Set the default output extension to
<samp>.mex</samp>.
</p>
</dd>
<dt>‘<samp>-s</samp>’</dt>
<dt>‘<samp>--strip</samp>’</dt>
<dd><p>Strip the output file.
</p>
</dd>
<dt>‘<samp>-v</samp>’</dt>
<dt>‘<samp>--verbose</samp>’</dt>
<dd><p>Echo commands as they are executed.
</p>
</dd>
<dt>‘<samp>file</samp>’</dt>
<dd><p>The file to compile or link. Recognized file types are:
</p>
<div class="example">
<pre class="example"> .c C source
.cc C++ source
.cp C++ source
.cpp C++ source
.CPP C++ source
.cxx C++ source
.c++ C++ source
.C C++ source
.f Fortran source (fixed form)
.F Fortran source (fixed form)
.f90 Fortran source (free form)
.F90 Fortran source (free form)
.o object file
.a library file
</pre></div>
</dd>
</dl>
</dd></dl>
<p>Consider the following short example which introduces the basics of writing a
C++ function that can be linked to Octave.
</p>
<div class="example">
<pre class="verbatim">#include <octave/oct.h>
DEFUN_DLD (helloworld, args, nargout,
"Hello World Help String")
{
octave_stdout << "Hello World has "
<< args.length () << " input arguments and "
<< nargout << " output arguments.\n";
// Return empty matrices for any outputs
octave_value_list retval (nargout);
for (int i = 0; i < nargout; i++)
retval(i) = octave_value (Matrix ());
return retval;
}
</pre></div>
<p>The first critical line is <code>#include <octave/oct.h></code> which makes available
most of the definitions necessary for a C++ oct-file. Note that
<samp>octave/oct.h</samp> is a C++ header and cannot be directly <code>#include</code>’ed
in a C source file, nor any other language.
</p>
<p>Included by <samp>oct.h</samp> is a definition for the macro <code><span class="nolinebreak">DEFUN_DLD</span></code><!-- /@w -->
which creates a dynamically loaded function. This macro takes four arguments:
</p>
<ol>
<li> The function name as it will be seen in Octave,
</li><li> The list of arguments to the function of type <code>octave_value_list</code>,
</li><li> The number of output arguments, which can be—and often is—omitted if
not used, and
</li><li> The string to use for the help text of the function.
</li></ol>
<p>The return type of functions defined with <code><span class="nolinebreak">DEFUN_DLD</span></code><!-- /@w --> is always
<code>octave_value_list</code>.
</p>
<p>There are a couple of important considerations in the choice of function name.
First, it must be a valid Octave function name and so must be a sequence of
letters, digits, and underscores not starting with a digit. Second, as Octave
uses the function name to define the filename it attempts to find the function
in, the function name in the <code><span class="nolinebreak">DEFUN_DLD</span></code><!-- /@w --> macro must match the filename
of the oct-file. Therefore, the above function should be in a file
<samp>helloworld.cc</samp>, and would be compiled to an oct-file using the command
</p>
<div class="example">
<pre class="example">mkoctfile helloworld.cc
</pre></div>
<p>This will create a file called <samp>helloworld.oct</samp> that is the compiled
version of the function. It should be noted that it is perfectly acceptable to
have more than one <code><span class="nolinebreak">DEFUN_DLD</span></code><!-- /@w --> function in a source file. However,
there must either be a symbolic link to the oct-file for each of the functions
defined in the source code with the <code><span class="nolinebreak">DEFUN_DLD</span></code><!-- /@w --> macro or the
<code>autoload</code> (<a href="Function-Files.html">Function Files</a>) function should be used.
</p>
<p>The rest of the function shows how to find the number of input arguments, how
to print through the Octave pager, and how to return from the function. After
compiling this function as above, an example of its use is
</p>
<div class="example">
<pre class="example">helloworld (1, 2, 3)
-| Hello World has 3 input arguments and 0 output arguments.
</pre></div>
<p>Subsequent sections show how to use specific classes from Octave’s core
internals. Base classes like <code>dMatrix</code> (a matrix of double values) are
found in the directory <samp>liboctave/array</samp>. The definitive reference for
how to use a particular class is the header file itself. However, it is often
enough simply to study the examples in the manual in order to be able to use a
class.
</p>
<hr>
<div class="header">
<p>
Next: <a href="Matrices-and-Arrays-in-Oct_002dFiles.html" accesskey="n" rel="next">Matrices and Arrays in Oct-Files</a>, Up: <a href="Oct_002dFiles.html" accesskey="u" rel="up">Oct-Files</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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