STL源码剖析之算法：iter_swap & swap

template <class ForwardIterator1, class ForwardIterator2, class T>
inline void __iter_swap(ForwardIterator1 a, ForwardIterator2 b, T*) {
    T tmp = *a;
    *a = *b;
    *b = tmp;
}

template <class ForwardIterator1, class ForwardIterator2>
inline void iter_swap(ForwardIterator1 a, ForwardIterator2 b) {
    __iter_swap(a, b, value_type(a));
}

template <class T>
inline void swap(T &a, T &b) {
    T tmp = a;
    a = b;
    b = tmp;
}