22 Containers library [containers]

22.5 Unordered associative containers [unord]

22.5.7 Class template unordered_­multiset [unord.multiset]

22.5.7.3 Erasure [unord.multiset.erasure]

template<class K, class H, class P, class A, class Predicate> void erase_if(unordered_multiset<K, H, P, A>& c, Predicate pred);
Effects: Equivalent to:
for (auto i = c.begin(), last = c.end(); i != last; ) {
  if (pred(*i)) {
    i = c.erase(i);
  } else {
    ++i;
  }
}