(octave.info)Overloading and Autoloading

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11.9.5 Overloading and Autoloading
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Functions can be overloaded to work with different input arguments.  For
example, the operator ’+’ has been overloaded in Octave to work with
single, double, uint8, int32, and many other arguments.  The preferred
way to overload functions is through classes and object oriented
programming (Note: Function Overloading).  Occasionally, however, one
needs to undo user overloading and call the default function associated
with a specific type.  The ‘builtin’ function exists for this purpose.

 -- : [...] = builtin (F, ...)
     Call the base function F even if F is overloaded to another
     function for the given type signature.

     This is normally useful when doing object-oriented programming and
     there is a requirement to call one of Octave’s base functions
     rather than the overloaded one of a new class.

     A trivial example which redefines the ‘sin’ function to be the
     ‘cos’ function shows how ‘builtin’ works.

          sin (0)
            ⇒ 0
          function y = sin (x), y = cos (x); endfunction
          sin (0)
            ⇒ 1
          builtin ("sin", 0)
            ⇒ 0

   A single dynamically linked file might define several functions.
However, as Octave searches for functions based on the functions
filename, Octave needs a manner in which to find each of the functions
in the dynamically linked file.  On operating systems that support
symbolic links, it is possible to create a symbolic link to the original
file for each of the functions which it contains.

   However, there is at least one well known operating system that
doesn’t support symbolic links.  Making copies of the original file for
each of the functions is undesirable as it increases the amount of disk
space used by Octave.  Instead Octave supplies the ‘autoload’ function,
that permits the user to define in which file a certain function will be
found.

 -- : AUTOLOAD_MAP = autoload ()
 -- : autoload (FUNCTION, FILE)
 -- : autoload (..., "remove")
     Define FUNCTION to autoload from FILE.

     The second argument, FILE, should be an absolute filename or a file
     name in the same directory as the function or script from which the
     autoload command was run.  FILE _should not_ depend on the Octave
     load path.

     Normally, calls to ‘autoload’ appear in PKG_ADD script files that
     are evaluated when a directory is added to Octave’s load path.  To
     avoid having to hardcode directory names in FILE, if FILE is in the
     same directory as the PKG_ADD script then

          autoload ("foo", "bar.oct");

     will load the function ‘foo’ from the file ‘bar.oct’.  The above
     usage when ‘bar.oct’ is not in the same directory, or usages such
     as

          autoload ("foo", file_in_loadpath ("bar.oct"))

     are strongly discouraged, as their behavior may be unpredictable.

     With no arguments, return a structure containing the current
     autoload map.

     If a third argument "remove" is given, the function is cleared and
     not loaded anymore during the current Octave session.

     See also: Note: PKG_ADD.