24 Containers library [containers]

24.5 Unordered associative containers [unord]

24.5.4 Class template unordered_­map [unord.map]

24.5.4.5 Erasure [unord.map.erasure]

template<class K, class T, class H, class P, class A, class Predicate> typename unordered_map<K, T, H, P, A>::size_type erase_if(unordered_map<K, T, H, P, A>& c, Predicate pred);
Effects: Equivalent to: auto original_size = c.size(); for (auto i = c.begin(), last = c.end(); i != last; ) { if (pred(*i)) { i = c.erase(i); } else { ++i; } } return original_size - c.size();