std::experimental::ranges::adjacent_find

Notwithstanding the declarations depicted above, the actual number and order of template parameters for algorithm declarations is unspecified. Thus, if explicit template arguments are used when calling an algorithm, the program is probably non-portable.

Parameters

Return value

An iterator to the first of the first pair of identical elements, that is, the first iterator i such that both i and i + 1 are in the range [first, last) and ranges::invoke (pred, ranges::invoke (proj, *i), ranges::invoke (proj, * (i + 1 ) ) ) ! = false

If no such elements are found, an iterator that compares equal to last is returned.

Complexity

If the range is nonempty, exactly min((result - first) + 1, (last - first) - 1) applications of the predicate where result is the return value, and at most twice as many applications of the projection.

Possible implementation

template<ForwardIterator I, Sentinel<I> S, class Proj = ranges::identity,
         IndirectRelation<projected<I, Proj>> Pred = ranges::equal_to<>>
I adjacent_find(I first, S last, Pred pred = Pred{}, Proj proj = Proj{})
{
    if (first == last)
        return first;
    I next = first;
    ++next;
    while (next != last)
    {
        if (ranges::invoke(pred, ranges::invoke(proj, *first),
                                 ranges::invoke(proj, *next)))
            return first;
        ++next;
        ++first;
    }
    return next;
}

Example

See also