std::convertible_to (since C++20)

 

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Symbols index

External libraries

 

Concepts library

Core language concepts same_as (C++20) derived_from (C++20) convertible_to (C++20) common_reference_with (C++20) common_with (C++20) integral (C++20) signed_integral (C++20) unsigned_integral (C++20) floating_point (C++20) swappableswappable_with (C++20)(C++20) destructible (C++20) constructible_from (C++20) default_initializable (C++20)   move_constructible (C++20) copy_constructible (C++20) assignable_from (C++20)

Comparison concepts equality_comparableequality_comparable_with (C++20)(C++20) totally_orderedtotally_ordered_with (C++20)(C++20) Object concepts movable (C++20) copyable (C++20) semiregular (C++20) regular (C++20) Callable concepts invocableregular_invocable (C++20)(C++20) predicate (C++20) relation (C++20) equivalence_relation (C++20) strict_weak_order (C++20)

Exposition-only concepts boolean-testable  (C++20)

 

Defined in header <concepts>
template< class From, class To > concept convertible_to =     std::is_convertible_v<From, To> &&     requires {         static_cast<To>(std::declval<From>());     };		(since C++20)

The concept convertible_to<From, To> specifies that an expression of the same type and value category as those of std::declval<From>() can be implicitly and explicitly converted to the type To, and the two forms of conversion produce equal results.

Semantic requirements

convertible_to<From, To> is modeled only if, given a function fun of type std::add_rvalue_reference_t<From>() such that the expression fun() is equality-preserving,

• Either
  • To is neither an object type nor a reference-to-object type, or
  • static_cast<To>(fun()) is equal to []() -> To { return fun(); }(), and

• One of the following is true:
  • std::add_rvalue_reference_t<From> is not a reference-to-object type, or
  • std::add_rvalue_reference_t<From> is an rvalue reference to a non-const-qualified type, and the resulting state of the object referenced by fun() is valid but unspecified after either expression above; or
  • the object referred to by fun() is not modified by either expression above.

Equality preservation

Expressions declared in requires expressions of the standard library concepts are required to be equality-preserving (except where stated otherwise).

References

• C++23 standard (ISO/IEC 14882:2024):

• 18.4.4 Concept convertible_to [concept.convertible]

• C++20 standard (ISO/IEC 14882:2020):

• 18.4.4 Concept convertible_to [concept.convertible]

See also

is_convertibleis_nothrow_convertible (C++11)(C++20)

checks if a type can be converted to the other type (class template)