Why does std::map::erase return int rather than bool?-CodePudding

I wonder why std::map::erase has an overload that returns an int that represents the number of elements erased; so as long as the elements are unique so the number is either 1 or 0. In this case why it doesn't return bool rather than an int?

     std::map<std::string, std::size_t> containers{
    {"map", 1}, {"set", 10}, {"map", 5}, {"vector", 4}, {"array", 7}
};

for(auto const& p : containers)
    std::cout << p.first << " " << p.second << '\n';

std::cout << containers.erase("map") << '\n'; // 1
std::cout << containers.erase("map") << '\n'; // 0

for(auto const& p : containers)
    std::cout << p.first << " " << p.second << '\n';

CodePudding user response：

The answer to your question becomes obvious once you consider what std::multimap::erase() returns.

That container's erase() method might return 0, it might return 1, or it might return some other value.

Having an interface that's consistent across containers allows for implementation of templates and algorithms that work equally well with either container, since the return value from erase(), whether it's from a map or a multimap, means exactly the same thing.

P.S. Without looking it up, you should be able to make a pretty good guess what std::set's and std::multiset's erase() methods return.

CodePudding user response：

All the c ordered associative containers are based off of a binary search tree, are related, and this is reflected in their similar interfaces.