< cpp‎ | experimental‎ | ranges
Technical Specification
Filesystem library (filesystem TS)
Library fundamentals (library fundamentals TS)
Library fundamentals 2 (library fundamentals TS v2)
Library fundamentals 3 (library fundamentals TS v3)
Extensions for parallelism (parallelism TS)
Extensions for parallelism 2 (parallelism TS v2)
Extensions for concurrency (concurrency TS)
Extensions for concurrency 2 (concurrency TS v2)
Concepts (concepts TS)
Ranges (ranges TS)
Reflection (reflection TS)
Mathematical special functions (special functions TR)
Experimental Non-TS
Pattern Matching
Linear Algebra
2D Graphics
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{} );
(1) (ranges TS)
template< ForwardRange R, class Proj = ranges::identity,

          IndirectRelation<projected<ranges::iterator_t<R>, Proj>> Pred = ranges::equal_to<> >

ranges::safe_iterator_t<R> adjacent_find( R&& r, Pred pred = Pred{}, Proj proj = Proj{} );
(2) (ranges TS)
1) Searches the range [firstlast) for two consecutive identical elements. Elements are compared using pred after being projected with proj.
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.

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.


[edit] Parameters

first, last - the range of elements to examine
r - the range of elements to examine
pred - predicate to use to compare the projected elements
proj - projection to apply to the elements

[edit] 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 [firstlast) 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.

[edit] 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.

[edit] 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;
    while (next != last)
        if (ranges::invoke(pred, ranges::invoke(proj, *first),
                                 ranges::invoke(proj, *next)))
            return first;
    return next;

[edit] Example

[edit] See also

finds the first two adjacent items that are equal (or satisfy a given predicate)
(function template) [edit]
removes consecutive duplicate elements in a range
(function template) [edit]