使用boost :: bind的std :: foreach

Question

What's wrong with this:

template <typename T>
std::list<T> & operator+=(std::list<T> & first, std::list<T> const& second)
{
    std::for_each(second.begin(), second.end(), boost::bind(&std::list<T>::push_back, first, _1));

    return first;
}

It compiles fine, but doesn't work.

Answer 1

You need to use boost::ref to pass an argument/object via reference, otherwise bind creates an internal copy.

std::for_each(
    second.begin(), second.end(),
    boost::bind(&std::list<T>::push_back, boost::ref(first), _1)
);

Answer 2

Note that while Cat Plus Plus's solution would work for you, the encouraged way to do such things in C++03 (before the advent if lambdas in the upcoming standard version) is to use the standard library algorithms and functors. Unfortunately, in some cases they get quite convoluted themselves, but in this case I think they produce clearer code:

std::copy(second.begin(), second.end(), std::back_inserter(first));

Answer 3

std::list<T> ls;
std::list<T> ls0;
// ...
ls.insert(ls.end(), ls0.begin(), ls0.end());