The documentation for an oct-file is contained in the fourth string parameter
of the DEFUN_DLD macro. This string can be formatted in the same
manner as the help strings for user functions, however there are some issues
that are particular to the formatting of help strings within oct-files.
The major issue is that the help string will typically be longer than a single line of text, and so the formatting of long multi-line help strings needs to be taken into account. There are several possible solutions, but the most common is illustrated in the following example,
DEFUN_DLD (do_what_i_want, args, nargout,
"-*- texinfo -*-\n\
@deftypefn {} {} do_what_i_say (@var{n})\n\
A function that does what the user actually wants rather\n\
than what they requested.\n\
@end deftypefn")
{
…
}
where each line of text is terminated by \n\ which is an embedded
newline in the string together with a C++ string continuation character. Note
that the final \ must be the last character on the line.
Octave also includes the ability to embed test and demonstration code for a
function within the code itself (see Test and Demo Functions). This can be
used from within oct-files (or in fact any file) with certain provisos. First,
the test and demo functions of Octave look for %! as the first two
characters of a line to identify test and demonstration code. This is a
requirement for oct-files as well. In addition, the test and demonstration
code must be wrapped in a comment block to avoid it being interpreted by the
compiler. Finally, the Octave test and demonstration code must have access to
the original source code of the oct-file—not just the compiled code—as the
tests are stripped from the compiled code. An example in an oct-file might be
/* %!assert (sin ([1,2]), [sin(1),sin(2)]) %!error (sin ()) %!error (sin (1,1)) */