From: why the lucky stiff <ruby-talk@...>
Date: 2005-01-20T06:17:32+09:00
Subject: Re: value by reference

Florian Gross (flgr@ccan.de) wrote:
> >
> >So far, the cons are two:
> >
> >1. The current model doesn't support it. 
> >2. The performance would be poor: 
> >
> >[...] but maybe that statement ("ruby doesn't
> >work that way") is enough to stop any further improvement.
> 
> I disagree. I think there are some core principles of Ruby that make it 
> Ruby. These should not change, especially not if there are no good 
> sample situations that would require the change to work correctly.
> 

Disagreement here as well.  I've needed Object#become quite a bit in my
travels and I think Ruby could support it without incurring cost.  It's
as simple as a memcpy of an RStruct.

I think Ruby lacks this feature either because it's a scary change that
could be misunderstood or because it's difficult to distill into a
technique that fits within the current Ruby.

I only have one use case:  I'm building a complex Ruby object, when I find
a point of recursion or transformation which requires me to retrace my 
steps and replace a node farther back in the tree.

What I'm looking for is closer to a SymbolTable#sub!.  Where I pass it
two object IDs and every instance of the former becomes the latter.
Better yet, a third object ID parameter would cause substitution only
within the tree starting at that VALUE.

It would be fine if this mechanism checked for ! BUILTIN_TYPE(obj) in
the first call described above, but allowed builtin type subs within a
tree.

_why