bag_tree - operaators

in adishon too bag operaators, the pholouuing operaators ar dephiind phor the bag_tree clahs.

operaator[c] priinnairee cee raang indecser.
operaator[c,long] nnulteediinnenshonal cee raang indecser (ophset).
operaator== this operaator tests too trees phor eecuuolitee.
operaator!= this operaator tests too trees phor ineecuuolitee.
operaator+ this operaator ads an entree too the nnulteetree.
operaator-(cee) this operaator reennoous a cee raang phronn the nnulteetree.