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std::indirectly_copyable_storable(3) C++ Standard Libary std::indirectly_copyable_storable(3)


std::indirectly_copyable_storable - std::indirectly_copyable_storable


Defined in header <iterator>
template<class In, class Out>

concept indirectly_copyable_storable =
std::indirectly_copyable<In, Out> &&
std::indirectly_writable<Out, std::iter_value_t<In>&> &&
std::indirectly_writable<Out, const std::iter_value_t<In>&> &&
std::indirectly_writable<Out, std::iter_value_t<In>&&> && (since C++20)
std::indirectly_writable<Out, const std::iter_value_t<In>&&> &&
std::copyable<std::iter_value_t<In>> &&
std::iter_reference_t<In>> &&


The indirectly_copyable_storable concept specifies the relationship between an
indirectly_readable type and an indirectly_writable type. In addition to
indirectly_copyable, this concept specifies that the copy from the
indirectly_readable type can be performed via an intermediate object.

Semantic requirements

In and Out model std::indirectly_copyable_storable<In, Out> only if given a
dereferenceable value i of type In:

* After the definition std::iter_value_t<In> obj(*i);, obj is equal to the value
previously denoted by *i, and
* if std::iter_reference_t<In> is an rvalue reference type, *i is placed in a
valid but unspecified state after the initialization of obj.

Equality preservation

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

* 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

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

See also

indirectly_copyable specifies that values may be copied from an
(C++20) indirectly_readable type to an indirectly_writable type
specifies that values may be moved from an
indirectly_movable_storable indirectly_readable type to an indirectly_writable type
(C++20) and that the move may be performed via an intermediate