/** XXX: could use mmap? */
void
-copy_in_bits (boost::filesystem::path from, boost::filesystem::path to, boost::function<void (float)> progress)
+copy_in_bits (boost::filesystem::path from, boost::filesystem::path to, std::function<void (float)> progress)
{
auto f = fopen_boost (from, "rb");
if (!f) {