NAME¶

std::indirectly_readable - std::indirectly_readable

Synopsis¶

Defined in header <iterator>
template< class In >

concept __IndirectlyReadableImpl = // exposition only
requires(const In in) {
typename std::iter_value_t<In>;
typename std::iter_reference_t<In>;
typename std::iter_rvalue_reference_t<In>;
{ *in } -> std::same_as<std::iter_reference_t<In>>;
{ ranges::iter_move(in) } ->
std::same_as<std::iter_rvalue_reference_t<In>>;
} && (since C++20)
std::common_reference_with<
std::iter_reference_t<In>&&, std::iter_value_t<In>&
> &&
std::common_reference_with<
std::iter_reference_t<In>&&, std::iter_rvalue_reference_t<In>&&
> &&
std::common_reference_with<
std::iter_rvalue_reference_t<In>&&, const std::iter_value_t<In>&

>;
template< class In >

concept indirectly_readable = (since C++20)

__IndirectlyReadableImpl<std::remove_cvref_t<In>>;

The concept indirectly_readable is modeled by types that are readable by applying
operator*, such as pointers, smart pointers, and input iterators.

Semantic requirements

Given a value i of type I, I models indirectly_readable only if all concepts it
subsumes are modeled and the expression *i is equality preserving.

Equality preservation

An expression is equality preserving if it results in equal outputs given equal
inputs.

* The inputs to an expression consist of its operands.
* The outputs of an expression consist of its result and all operands modified by
the expression (if any).

In specification of standard concepts, operands are defined as the largest
subexpressions that include only:

* an id-expression, and
* invocations of std::move, std::forward, and std::declval.

The cv-qualification and value category of each operand is determined by assuming
that each template type parameter denotes a cv-unqualified complete non-array object
type.

Every expression required to be equality preserving is further required to be
stable: two evaluations of such an expression with the same input objects must have
equal outputs absent any explicit intervening modification of those input objects.

Unless noted otherwise, every expression used in a requires-expression is required
to be equality preserving and stable, and the evaluation of the expression may
modify only its non-constant operands. Operands that are constant must not be
modified.