...

...

This way one can write things like:

vector<T> v; push_back(v, istream_range<T>(ifstream("some_file.txt")));

Of course, one must be careful with such things.

Can you spot the bug in the following?

BOOST_FOREACH(const string& s, istream_range<string>(ifstream("some_file.txt"))) cout<< s;

Wouldn't that fail to compile if the istream_range is not copyable, but movable?

It's worse than that, I'm afraid. It does compile, but produces a silent runtime error. The problem is that the lifetime of the temporary ifstream object does not extend to the entire loop. The BOOST_FOREACH expands to something like this: for (const auto& __range = istream_range<string>(ifstream("some_file.txt")); // ... conditions that make sure this loop only runs once ... ) // ... other loops that introduce iterators etc. ... { cout << s; } The temporary istream_range object will live throughout the loop because a constant reference to it is maintained; however, the temporary ifstream object which the istream_range object holds a reference to (indirectly via its istream_iterators), will get destructed as soon as the for loop's init-statement finishes executing. As a result, the loop will try to read from an ifstream object that's already destructed, which of course is undefined behaviour. Note that this problem doesn't occur if you instead do: for_each(istream_range<string>(ifstream("some_file.txt")), [](const string& s){ cout << s; }); In this case, the loop is contained within the statement that declares the ifstream temporary, so everything is fine. Regards, Nate.