std::vector<int> ns{1, 5, 6, 0, 7, 2, 3, 8, 3, 0, 2, 1};

std::cout << "ns = { ";

for (auto&& i : ns) {

std::cout << i << ' ';

}

std::cout << "}\n";

// like filter() but only shows elements that are false under the predicate

std::cout << "Greater than 4\n";

for (auto&& i : iter::filterfalse(greater_than_four, ns)) {

std::cout << i << '\n';

}

// single argument version only shows falsey values

std::cout << "filterfalse(ns):\n";

for (auto&& i : iter::filterfalse(ns)) {

std::cout << i << '\n';

}

// only print non-empty strings

std::vector<std::string> words {"hello", "", "", "world", "", "goodbye", ""};

for (auto&& s : iter::filterfalse(&std::string::empty, words)) {

std::cout << s << '\n';

}