On 10/6/10 5:32 AM, Jeffrey Lee Hellrung, Jr. wrote:
On 10/05/2010 02:11 PM, Christophe Henry wrote:
Hi,
I have 2 fusion containers: a small vector (my_vec) and a bigger set (my_set). I want to overwrite the elements of the set with elements from the vector whenever they have the same type. Sounds simple:
struct update { update(my_set_type& to_overwrite_):to_overwrite(to_overwrite_){} template<typename T> void operator()(T& elt) /*const?*/ { boost::fusion::at_key<T>(to_overwrite)=elt; } my_set_type& to_overwrite; };
boost::fusion::for_each(my_vec,update(my_set));
Except that this won't compile because the operator() is required to be const, which is sad, because it was very simple.
And it won't compile *with* the const? I don't think the const'ness of the member function affects the const'ness of the referent of to_overwrite.
That said, it does look the documentation for boost::fusion::for_each (indicating that F is received by value) contradicts the source code (where F is received by reference-to-const)...
Jeffrey, I don't see that here (F is received by value): http://tinyurl.com/2vdao6r. Do you? Henry, could you provide some code I can try? const should be OK and I don't see any reason why not. Regards, -- Joel de Guzman http://www.boostpro.com http://spirit.sf.net