On 1/8/2011 9:06 AM, Hossein Haeri wrote:
Hi Eric,
Does the fact that I store formula_ by value (as in line ***) shoot the trouble of dangling references?
No, the problem still exists. You're storing the outer-most node by value, but all the inner nodes (temporary objects constructed while building the expression) are held by reference. At the very least, the constructor of MyClass needs to pass the incoming expression through deep_copy.
So, what about the following?
#define DEFINE_MY_CLASS(name, exp) \ MyClass<result_of::deep_copy<BOOST_TYPEOF(exp)>::type> name(deep_copy(exp))
Sure. Or you could move the deep-copy action an implementation detail of MyClass and keep the macro simple. Whichever.
That article takes a sequence of function calls and turns them into a single callable object. You're taking a sequence of function calls and are turning them into a callable object.
I see. OK, so you're basically saying that the >> syntax can be avoided and that we can use simple function object composition instead with no need for Protofication.
No, I'm not saying that. I'm saying you can use >> and Proto to build an expression tree, and use a transform to compose that tree into a function object. But the principles of that transformation are the same as what's described in the article. Once you have the composed function as a function object, you can store it in a boost::function. -- Eric Niebler BoostPro Computing http://www.boostpro.com