std::incrementable_traits - cppreference.com

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Defined in header `<iterator>`
`template< class I > struct incrementable_traits {};`	(1)	(since C++20)
`template< class T > requires std::is_object_v<T> struct incrementable_traits<T*>;`	(2)	(since C++20)
`template< class T > struct incrementable_traits<const T> : incrementable_traits<T> {};`	(3)	(since C++20)
`template< class T > requires requires { typename T::difference_type; } struct incrementable_traits<T>;`	(4)	(since C++20)
`template< class T > requires (!requires { typename T::difference_type; }) && requires(const T& a, const T& b) { { a - b } -> std::integral; } struct incrementable_traits<T>;`	(5)	(since C++20)

Computes the associated difference type of the type I, if any. A program may specialize incrementable_traits for a program-defined type.

1) Primary template is an empty struct.

2) Specialization for pointers.

Provides a member type difference_type same as std::ptrdiff_t.

3) Specialization for const-qualified types.

4) Specialization for types that define a public and accessible member type difference_type.

Provides a member type difference_type same as T::difference_type.

5) Specialization for types that do not define a public and accessible member type difference_type but do support subtraction.

Provides a member type difference_type same as std::make_signed_t<decltype(std::declval<T>() - std::declval<T>())>. The implicit expression variations rule (see below) applies to the expression a - b.

Implicit expression variations

A requires expression that uses an expression that is non-modifying for some constant lvalue operand also requires implicit expression variations.

Implicit expression variations

Example

See also