On 3/4/2010 4:21 PM, Manjunath Kudlur wrote:
proto::make_expr tries to enforce uniformity in the trees it returns. In particular, it wants all the child nodes to be in the same domain as the parent node it returns. When the domains don't match (as they don't in this case because int32_ is in the default_domain), it passes the child through the domain's generator.
I follow you up to here.
The result gets stored by value instead of by reference as you're requesting.
I lost you here. In my case, I pass program_() and boost::ref(a0) as children to make_expr. My generator would match otherwise(_) rule (I don't have it in the program I sent, but suppose I add it to program_generator). So the result is the expression unmodified, no? What gets stored by value, where, like you say?
Well, your domain's generator is a little unusual in that not all the expressions it generates are, in fact, within your domain. That's not a stated post-condition of the Generator parameter, but it probably should be. In short, make_expr is assuming that the generator is returning a new object, and so it is storing it by value. I could hack Proto to make this case work, but doing so makes me uncomfortable. I don't think I want to support generators that don't return expressions in the right domain. -- Eric Niebler BoostPro Computing http://www.boostpro.com