cpp/utility/tuple element

Provides compile-time indexed access to the types of the elements of a type.

@1@ The primary template is not defined. An explicit (full) or partial specialization is required to make a type tuple-like.

@2-4@ Specializations for cv-qualified types simply add corresponding cv-qualifiers by default.

Specializations
The standard library provides following specializations for standard library types:

Users may specialize for program-defined types to make them tuple-like.

In normal cases where the functions returns reference members or reference to subobjects, only specializations for cv-unqualified types are needed to be customized.