< cpp‎ | iterator
Iterator library
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Defined in header <iterator>
template< class I1, class I2 >

concept indirectly_swappable =
    std::indirectly_readable<I1> &&
    std::indirectly_readable<I2> &&
    requires( const I1 i1, const I2 i2 ) {
        ranges::iter_swap(i1, i1);
        ranges::iter_swap(i1, i2);
        ranges::iter_swap(i2, i1);
        ranges::iter_swap(i2, i2);

(since C++20)

The concept indirectly_swappable specifies a relationship between two types respectively modelling std::indirectly_readable, where their referenced types can be swapped.

[edit] Semantic requirements

I1 and I2 model indirectly_swappable only if all concepts it subsumes are modeled.

[edit] 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:

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 only modify its non-constant operands. Operands that are constant must not be modified.

[edit] See also

specifies that a type is indirectly readable by applying operator *
(concept) [edit]
swap the values referenced by two dereferenceable objects
(customization point object) [edit]