NAME¶

std::experimental::ranges::search_n - std::experimental::ranges::search_n

Synopsis¶

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> (1) (ranges TS)
I search_n(I first, S last, ranges::difference_type_t<I> count,

const T& value, Pred pred = Pred{}, Proj proj = Proj{});
template< ForwardRange R, class T, class Pred = ranges::equal_to<>,

class Proj = ranges::identity >
requires IndirectlyComparable<ranges::iterator_t<R>, const T*, Pred,
Proj> (2) (ranges TS)
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{});

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)
find finds the first element satisfying specific criteria
find_if (function template)
find_if_not
search searches for a range of elements
(function template)