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std::convertible_to

From cppreference.com
< cpp‎ | concepts
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.

[edit] 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.

[edit] Equality preservation

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

[edit] See also

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