# std::experimental::ranges::find_first_of

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< cpp‎ | experimental‎ | ranges

Defined in header `<experimental/ranges/algorithm>` |  |
template< InputIterator I1, Sentinel<I1> S1, ForwardIterator I2, Sentinel<I2> S2, class Proj1 = ranges::identity, class Proj2 = ranges::identity, IndirectRelation< projected <I1, Proj1>, projected <I2, Proj2>> Pred = ranges::equal_to <> > I1 find_first_of( I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = Pred{}, Proj1 proj1 = Proj1{}, Proj2 proj2 = Proj2{} ); | (1) | (ranges TS)
template< InputRange R1, ForwardRange R2, class Proj1 = ranges::identity, class Proj2 = ranges::identity, IndirectRelation< projected < ranges::iterator_t <R1>, Proj1>, projected < ranges::iterator_t <R2>, Proj2>> Pred = ranges::equal_to <> > ranges::safe_iterator_t <R1> find_first_of( R1&& r1, R2&& r2, Pred pred = Pred{}, Proj1 proj1 = Proj1{}, Proj2 proj2 = Proj2{} ); | (2) | (ranges TS)

1) Searches the range `[`first1`,` last1`)` for any of the elements in the range `[`first2`,` last2`)`, after projecting the ranges with proj1 and proj2 respectively. The projected elements are compared using pred.
2) Same as (1), but uses r1 as the first source range and r2 as the second source range, as if using ranges::begin (r1) as first1, ranges::end (r1) as last1, ranges::begin (r2) as first2, and ranges::end (r2) as last2.

### Parameters

first1, last1 | - | the range of elements to examine
r1 | - | the range of elements to examine
first2, last2 | - | the range of elements to search for
r2 | - | the range of elements to search for
pred | - | predicate to use to compare the projected elements with
proj1 | - | projection to apply to the elements in the first range
proj2 | - | projection to apply to the elements in the second range

### Return value

Iterator to the first element in the range `[`first1`,` last1`)` that is equal to an element from the range `[`first2`,` last2`)` after projection. If no such element is found, an iterator comparing equal to last1 is returned.

### Complexity

At most `(S * N)` applications of the predicate and each projection, where S = distance(last2 - first2) and N = last1 - first1.

### Possible implementation

    template<InputIterator I1, Sentinel<I1> S1, ForwardIterator I2, Sentinel<I2> S2,
             class Proj1 = ranges::identity, class Proj2 = ranges::identity,
             IndirectRelation<projected<I1, Proj1>,
                              projected<I2, Proj2>> Pred = ranges::equal_to<>>
    I1 find_first_of(I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = Pred{},
                     Proj1 proj1 = Proj1{}, Proj2 proj2 = Proj2{})
    {
        for (; first1 != last1; ++first1)
            for (ForwardIt it = first2; it != last2; ++it)
                if (ranges::invoke(pred, ranges::invoke(proj1, *first1),
                                         ranges::invoke(proj2, *it)))
                    return first1;
        return first1;
    }

### Example

| This section is incomplete Reason: no example

### See also

find_first_of | searches for any one of a set of elements (function template)
findfind_iffind_if_not | finds the first element satisfying specific criteria (function template)

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