std:: convertible_to

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

See also

is_convertible is_nothrow_convertible (C++11) (C++20)

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