std::indirectly_movable_storable

template<class In, class Out>
concept indirectly_movable_storable =
    std::indirectly_movable<In, Out> &&
    std::indirectly_writable<Out, std::iter_value_t<In>> &&
    std::movable<std::iter_value_t<In>> &&
    std::constructible_from<std::iter_value_t<In>, std::iter_rvalue_reference_t<In>> &&
    std::assignable_from<std::iter_value_t<In>&, std::iter_rvalue_reference_t<In>>;

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

Semantic requirements

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

• After the definition std::iter_value_t<In> obj(ranges::iter_move(i));, obj is equal to the value previously denoted by *i, and
• if std::iter_rvalue_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 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.

See also