# std::experimental::ranges::search_n

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< cpp‎ | experimental‎ | ranges

Defined in header `<experimental/ranges/algorithm>` |  |
template< ForwardIterator I, Sentinel <I> S, class T, class Pred = ranges::equal_to <>, class Proj = ranges::identity > requires IndirectlyComparable <I, const T*, Pred, Proj> I search_n(I first, S last, ranges::difference_type_t<I> count, const T& value, Pred pred = Pred{}, Proj proj = Proj{}); | (1) | (ranges TS)
template< ForwardRange R, class T, class Pred = ranges::equal_to <>, class Proj = ranges::identity > requires IndirectlyComparable <ranges::iterator_t<R>, const T*, Pred, Proj> ranges::safe_iterator_t <R> search_n(R&& r, ranges::difference_type_t<ranges::iterator_t<R>> count, const T& value, Pred pred = Pred{}, Proj proj = Proj{}); | (2) | (ranges TS)

1) Searches the range `[first, last)` for the first sequence of `count` elements whose projected values are each equal to the given value `value` according to the predicate `pred`.
2) Same as (1), but uses `r` as the source range, as if using ranges::begin(r) as `first` and ranges::end(r) as `last`.

### Parameters

first, last | - | the range of elements to examine
r | - | the range of elements to examine
count | - | the length of the sequence to search for
value | - | the value to search for
pred | - | the predicate that compares the projected elements with `value`
proj | - | the projection to apply to the elements

### Return value

Iterator to the beginning of the found sequence in the range `[first, last)`. If no such sequence is found, an iterator that compares equal to `last` is returned.

### Complexity

At most `last - first` applications of the predicate and the projection.

### Possible implementation

    template< ForwardIterator I, Sentinel<I> S, class T,
              class Pred = ranges::equal_to<>, class Proj = ranges::identity >
      requires IndirectlyComparable<I, const T*, Pred, Proj>
    I search_n(I first, S last, ranges::difference_type_t<I> count,
               const T& value, Pred pred = Pred{}, Proj proj = Proj{})
    {
        for(; first != last; ++first) {
            if (!ranges::invoke(pred, ranges::invoke(proj, *first), value)) {
                continue;
            }

            I candidate = first;
            ranges::difference_type_t<I> cur_count = 0;

            while (true) {
                ++cur_count;
                if (cur_count == count) {
                    // success
                    return candidate;
                }
                ++first;
                if (first == last) {
                    // exhausted the list
                    return first;
                }
                if (!ranges::invoke(pred, ranges::invoke(proj, *first), value)) {
                    // too few in a row
                    break;
                }
            }
        }
        return first;
    }

### Example

| This section is incomplete Reason: no example

### See also

search_n | searches a range for a number of consecutive copies of an element (function template)
find_end | finds the last sequence of elements in a certain range (function template)
findfind_iffind_if_not | finds the first element satisfying specific criteria (function template)
search | searches for a range of elements (function template)

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