From: ts <decoux@...>
Date: 2001-06-27T00:04:30+09:00
Subject: [ruby-talk:16905] Re: rb_define_method when argc is -1

>>>>> "L" == Laurent Julliard <Laurent.Julliard@xrce.xerox.com> writes:

L> I have a piece of code under my eyes where rb_define_method is called
L> with the argc parameter at -1. Is this a documented feature of the
L> function and if so what does it do exactly ?

 See README.EXT


2.1.2 Method/singleton method definition

To define methods or singleton methods, use functions below:

  void rb_define_method(VALUE klass, const char *name, 
                        VALUE (*func)(), int argc)

  void rb_define_singleton_method(VALUE object, const char *name, 
                                  VALUE (*func)(), int argc)

The `argc' represents the number of the arguments to the C function,
which must be less than 17.  But I believe you don't need that much. :-)

If `argc' is negative, it specifies calling sequence, not number of
the arguments.  

If argc is -1, the function will be called like:

  VALUE func(int argc, VALUE *argv, VALUE obj)

where argc is the actual number of arguments, argv is the C array of
the arguments, and obj is the receiver.

if argc is -2, the arguments are passed in Ruby array. The function
will be called like:

  VALUE func(VALUE obj, VALUE args)

where obj is the receiver, and args is the Ruby array containing
actual arguments.



Guy Decoux