std::convertible_to

 

C++

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Named requirements

Feature test macros (C++20)

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Concepts library (C++20)

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Technical specifications

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(std::add_rvalue_reference_t<From> (&f)()) {     static_cast<To>(f());   };		(since C++20)

The concept convertible_to<From, To> specifies that an expression of the type and value category specified by From can be implicitly and explicitly converted to the type To, and the two forms of conversion are equivalent.

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 (see below),

• 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).

See also

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

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