[boost] Re: [spirit] rule<> and copying

From: Eric Niebler (eric_at_[hidden])
Date: 2004-05-27 12:44:54

Eric Niebler wrote:

> 
> There is another solution. Give rules value semantics by default as I 
> suggest, but require people to use special syntax to get reference 
> semantics. 

I hate replying to myself. ;-) I realize this doesn't give true value 
semantics. A rule which refers to itself (that is, it indirectly stores 
a pointer to itself) cannot be copied around and put inside containers 
and whatnot. Then I thought that it could be solved with an extra layer 
of indirection -- shared_ptr to a shared_ptr (ugh!) but then you have 
problems with cyclic references. Hence Joel's comment about garbage 
collection -- he's probably been through this thought process before.

I think I need to think it out again.

-- 
Eric Niebler
Boost Consulting
www.boost-consulting.com