Prashant Thakre ha escrito:
Hi,
OK, here, instead of a composite_key instantiation, you can take advantage directly of std::vector comparison semantics (you don't really need tuple_element):
typedef multi_index_container< element, indexed_by< hashed_unique< member<element,std::vector<const std::string>,&element::tp> > // other indices, maybe
element_collection;
Is this equivalent to having a member std::string tp which is constructed at run-time from all the elements of std::vector< const std::string > ?
Depends on how you construct that string: if you just concatenate the vector elements, then no, it's not equivalent. For instance, the following two vectors {"mast","err","apparent"} {"master","rap","parent"} both map to "masterrapparent".
Also, how does the hash function generate the key ?
Boost.Hash combines the vector element's hash values as described at http://boost.org/doc/html/id2490467.html B.MI also lets you specify your own hashing mechanism if you need it: http://boost.org/libs/multi_index/doc/advanced_topics.html#hash_spec
Thanks a lot.
regards, Prashant Thakre
Joaquín M López Muñoz Telefónica, Investigación y Desarrollo