# 11 Algorithms library [algorithms]

## 11.3 Non-modifying sequence operations [alg.nonmodifying]

### 11.3.7 Find first of [alg.find.first.of]

``` template <InputIterator I1, Sentinel<I1> S1, ForwardIterator I2, Sentinel<I2> S2, class Proj1 = identity, class Proj2 = identity, IndirectRelation<projected<I1, Proj1>, projected<I2, Proj2>> Pred = equal_to<>> I1 find_first_of(I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = Pred{}, Proj1 proj1 = Proj1{}, Proj2 proj2 = Proj2{}); template <InputRange Rng1, ForwardRange Rng2, class Proj1 = identity, class Proj2 = identity, IndirectRelation<projected<iterator_t<Rng1>, Proj1>, projected<iterator_t<Rng2>, Proj2>> Pred = equal_to<>> safe_iterator_t<Rng1> find_first_of(Rng1&& rng1, Rng2&& rng2, Pred pred = Pred{}, Proj1 proj1 = Proj1{}, Proj2 proj2 = Proj2{}); ```

Effects: Finds an element that matches one of a set of values.

Returns: The first iterator i in the range [first1,last1) such that for some iterator j in the range [first2,last2) the following condition holds: invoke(pred, invoke(proj1, *i), invoke(proj2, *j)) != false. Returns last1 if [first2,last2) is empty or if no such iterator is found.

Complexity: At most (last1-first1) * (last2-first2) applications of the corresponding predicate and the two projections.