Leitura de configuração em C++

config.h

auto after(const Key &prefix) const -> std::unordered_set<Key> {
	std::unordered_set<Key> values;
	iterate_and_check(prefix, [&values, &prefix](const std::pair<Key,Value> &pair) {
		values.insert( pair.first.substr( prefix.size() ) );
	});
	return values;
}

auto next_token(const Key &prefix, const typename Key::value_type separator) const -> std::unordered_set<Key> {
	std::unordered_set<Key> values;
	int pos = last_of(prefix, separator);
	iterate_and_check(prefix, [&values, &prefix, &pos, &separator](const std::pair<Key,Value> &pair) {
		int npos = next_of(pair.first, pos, separator);
		values.insert( pair.first.substr( pos, npos ) );
	});
	return values;
}