From: stillflame@...
Date: 2002-06-02T15:15:14+09:00
Subject: Method arity without instantiating an object

Well,
after a grueling week of hacking through ruby source,
we are failing at this particular task. 

Is there any way, given a method id and a class, to get the method's arity? 

what is known and basically understood: 

* a Method object is just a struct METHOD Data_Wrap_Struct'ed.
* the struct's member 'body' is a NODE* that is the actual doing stuff part 
of the method.
* only the NODE* is needed to determine the arity 

so we're almost there, if it weren't for NODE*'s.  there are all the weird 
macros - nd_next, nd_args, &c. - that act on the super crazy RNode (NODE) 
thingy to get it to act like any number of things, as dictated by the flags. 
in eval.c:mnew(), a few of these are set, but not all of the particular ones 
that are used by eval.c:method_arity(), so we're guessing that there's 
either overlap between them in their placement in the RNode structure, and 
it all works out magically, or there's some behind-the-scenes magic 
happening on the NODEs sometime between mnew and method_arity. 

this magic, whichever it may be, is that part that we're unable to grok.  
and maybe we're just fuzzy-headed from working on this, but some help would 
be greatly appreciated. 

martin chase - stillflame at FaerieMUD dot org