How to read arbitrary number of values using std::copy?

Question

I\'m trying to code opposite action to this:

std::ostream outs; // properly initialized of course
std::set my_set; // ditto

outs << my_set.         


        

Answer 1

You could derive from the istream_iterator.
Though using Daemin generator method is another option, though I would generate directly into the set rather than use an intermediate vector.

#include 
#include 
#include 
#include 


template
struct CountIter: public std::istream_iterator
{
    CountIter(size_t c)
        :std::istream_iterator()
        ,count(c)
    {}
    CountIter(std::istream& str)
        :std::istream_iterator(str)
        ,count(0)
    {}

    bool operator!=(CountIter const& rhs) const
    {
        return (count != rhs.count) && (dynamic_cast const&>(*this) != rhs);
    }
    T operator*()
    {
        ++count;
        return std::istream_iterator::operator*();
    }

    private:
        size_t  count;
};

int main()
{
    std::set       x;

    //std::copy(std::istream_iterator(std::cin),std::istream_iterator(),std::inserter(x,x.end()));
    std::copy(
                CountIter(std::cin),
                CountIter(5),
                std::inserter(x,x.end())
            );
}