NAME¶

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

Synopsis¶

subrange() requires std::default_initializable<I> = default; (1) (since
C++20)
constexpr subrange( /*convertible-to-non-slicing*/<I> auto i, S s ) (2) (since
requires (!/*store-size*/); C++20)
constexpr subrange( /*convertible-to-non-slicing*/<I> auto i, S s,

/*make-unsigned-like-t*/<std::iter_difference_t<I>> (3) (since
n ) C++20)

requires (K == ranges::subrange_kind::sized);
template< /*different-from*/<subrange> R >

requires ranges::borrowed_range<R> &&
/*convertible-to-non-slicing*/<ranges::iterator_t<R>, I> && (4) (since
std::convertible_to<ranges::sentinel_t<R>, S> C++20)

constexpr subrange( R&& r ) requires (!/*store-size*/ ||
ranges::sized_range<R>);
template< ranges::borrowed_range R>

requires /*convertible-to-non-slicing*/<ranges::iterator_t<R>, I> &&
std::convertible_to<ranges::sentinel_t<R>, S>
constexpr subrange( R&& r, (5) (since
/*make-unsigned-like-t*/<std::iter_difference_t<I>> n ) C++20)
requires (K == ranges::subrange_kind::sized)
: subrange{ranges::begin(r), ranges::end(r), n}

{}

Constructs a subrange.

If K == ranges::subrange_kind::sized && !std::sized_sentinel_for<S, I>, the size of
the range is stored into the subrange, as if stored by a member subobject of type
/*make-unsigned-like-t*/<std::iter_difference_t<I>>, where make-unsigned-like-t is
an exposition-only alias template that maps each integer-like type to its
corresponding unsigned version. Otherwise, the size is not stored. The constant
store-size is true if the size is stored, false otherwise.

1) Default constructor. Value-initializes the stored iterator and sentinel as if by
default member initializers = I() and = S(), respectively. If the size is stored, it
is initialized with 0 as if by the default member initializer = 0.
2) Constructs a subrange from an iterator-sentinel pair. Initializes the stored
iterator and sentinel with std::move(i) and s respectively. The behavior is
undefined if [i, s) is not a valid range.
3) Constructs a subrange from an iterator-sentinel pair and a size hint. Initializes
the stored iterator and sentinel with std::move(i) and s respectively. If the size
is stored, it is initialized with n. The behavior is undefined if [i, s) is not a
valid range, or n is not equal to ranges::distance(i, s) explicitly converted to its
type.
4) Constructs a subrange from a range. Equivalent to subrange(r,
static_cast</*make-unsigned-like-t*/<std::iter_difference_t<I>>>(ranges::size(r)))
if the size is stored. Otherwise, equivalent to subrange(ranges::begin(r),
ranges::end(r)).
5) Constructs a subrange from a range and a size hint. The behavior is undefined if
n is not equal to ranges::distance(ranges::begin(r), ranges::end(r)) explicitly
converted to its type.

The exposition only concept different-from is modeled by types T and U if and only
if std::decay_t<T> and std::decay_t<U> are different types.

The exposition only concept convertible-to-non-slicing is satisfied or modeled by
From and To if and only if std::convertible_to<From, To> is satisfied or modeled
respectively, and any of following conditions is satisfied:

* either std::decay_t<From> or std::decay_t<To> is not a pointer type,
* std::remove_pointer_t<From>(*)[] is implicitly convertible to
std::remove_pointer_t<To>(*)[], i.e., the conversion from From to To is at most
a qualification conversion.

Parameters¶

i - iterator that denotes the beginning of the range
s - sentinel that denotes the end of the range
r - range
n - size hint, must be equal to the size of the range

Notes¶

The exposition-only concept convertible-to-non-slicing forbids the conversion from
the pointer to derived class to the pointer to base class.

Defect reports

The following behavior-changing defect reports were applied retroactively to
previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 3470 C++20 convertible-to-non-slicing rejected some valid made accepted
qualification conversions
P2393R1 C++20 implicit conversion to an integer-class type made explicit
might be invalid

Example¶

This section is incomplete
Reason: no example

Category:¶

* Todo no example