[Boost-users] [range] strange behaviour with range-based for loop and adaptors

12 Mar 2011

      Hello,

I am experiencing some strange behaviour when using adaptors with a range-based for loop.

Here's what I'm trying:

#include <vector>
#include <iostream>
#include <boost/foreach.hpp>
#include <boost/range/adaptor/transformed.hpp>

std::vector<int> f()
{
    return std::vector<int>{1, 2, 3, 4};
}

int add1(int x) { return x + 1; }

int main()
{
    for (int i : f() | boost::adaptors::transformed(add1))
        std::cout << i << ' ';
    std::cout << '\n';
}

The output is 1 3 4 5, instead of the 2 3 4 5 that I would expect.

Is there something funny going on with temporaries?
Does the temporary returned by f() not stick around for the duration of the loop?

Thanks,
Nate.

[Boost-users] [range] strange behaviour with range-based for loop and adaptors

Nathan Ridge