NAME¶

std::ranges::subrange - std::ranges::subrange

Synopsis¶

Defined in header <ranges>
template<

std::input_or_output_iterator I,
std::sentinel_for<I> S = I,
ranges::subrange_kind K = std::sized_sentinel_for<S, I> ?
ranges::subrange_kind::sized : ranges::subrange_kind::unsized (since C++20)
>
requires (K == ranges::subrange_kind::sized ||
!std::sized_sentinel_for<S, I>)

class subrange : public ranges::view_interface<subrange<I, S, K>>

The subrange class template combines together an iterator and a sentinel into a
single view.

Additionally, the subrange is a sized_range whenever the final template parameter is
subrange_kind::sized (which happens when std::sized_sentinel_for<S, I> is satisfied
or when size is passed explicitly as a constructor argument). The size record is
needed to be stored if and only if std::sized_sentinel_for<S, I> is false and K is
subrange_kind::sized.

Member functions¶

constructor creates a new subrange
(C++20) (public member function)
operator PairLike converts the subrange to a pair-like type
(C++20) (public member function)

Observers¶

begin obtains the iterator
(C++20) (public member function)
end obtains the sentinel
(C++20) (public member function)
empty checks whether the subrange is empty
(C++20) (public member function)
size obtains the size of the subrange
(C++20) (public member function)

Iterator operations¶

advance advances the iterator by given distance
(C++20) (public member function)
prev obtains a copy of the subrange with its iterator decremented by a
(C++20) given distance
(public member function)
next obtains a copy of the subrange with its iterator advanced by a
(C++20) given distance
(public member function)
Inherited from std::ranges::view_interface
cbegin returns a constant iterator to the beginning of the range.
(C++23) (public member function of std::ranges::view_interface<D>)
cend returns a sentinel for the constant iterator of the range.
(C++23) (public member function of std::ranges::view_interface<D>)
operator bool returns whether the derived view is not empty. Provided if
(C++20) ranges::empty is applicable to it.
(public member function of std::ranges::view_interface<D>)
data gets the address of derived view's data. Provided if its iterator
(C++20) type satisfies contiguous_iterator.
(public member function of std::ranges::view_interface<D>)
front returns the first element in the derived view. Provided if it
(C++20) satisfies forward_range.
(public member function of std::ranges::view_interface<D>)
back returns the last element in the derived view. Provided if it
(C++20) satisfies bidirectional_range and common_range.
(public member function of std::ranges::view_interface<D>)
operator[] returns the n^th element in the derived view. Provided if it
(C++20) satisfies random_access_range.
(public member function of std::ranges::view_interface<D>)

Deduction guides

Non-member functions¶

get(std::ranges::subrange) obtains iterator or sentinel from a std::ranges::subrange
(C++20) (function template)

Helper types¶

ranges::subrange_kind specifies whether a std::ranges::subrange
(C++20) models std::ranges::sized_range
(enum)
std::tuple_size<std::ranges::subrange> obtains the number of components of a
(C++20) std::ranges::subrange
(class template specialization)
std::tuple_element<std::ranges::subrange> obtains the type of the iterator or the
(C++20) sentinel of a std::ranges::subrange
(class template specialization)

Helper templates

template< class I, class S, ranges::subrange_kind K >
inline constexpr bool enable_borrowed_range<ranges::subrange<I, S, K>> = true;

This specialization of std::ranges::enable_borrowed_range makes subrange satisfy
borrowed_range.

Example¶

// Run this code

#include <iostream>
#include <map>
#include <ranges>
#include <string_view>

template<class V>
void mutate(V& v)
{
v += 'A' - 'a';
}

template<class K, class V>
void mutate_map_values(std::multimap<K, V>& m, K k)
{
auto [first, last] = m.equal_range(k);
for (auto& [_, v] : std::ranges::subrange(first, last))
mutate(v);
}

int main()
{
auto print = [](std::string_view rem, auto const& mm)
{
std::cout << rem << "{ ";
for (const auto& [k, v] : mm)
std::cout << '{' << k << ",'" << v << "'} ";
std::cout << "}\n";
};

std::multimap<int, char> mm{{4,'a'}, {3,'-'}, {4,'b'}, {5,'-'}, {4,'c'}};
print("Before: ", mm);
mutate_map_values(mm, 4);
print("After: ", mm);
}

Output:¶

Before: { {3,'-'} {4,'a'} {4,'b'} {4,'c'} {5,'-'} }
After: { {3,'-'} {4,'A'} {4,'B'} {4,'C'} {5,'-'} }

See also¶

ranges::view_interface helper class template for defining a view, using the
(C++20) curiously recurring template pattern
(class template)