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The curiously recurring template pattern (CRTP) is an idiom, originally in C++, in which a class X derives from a class template instantiation using X itself as a template argument. [1] More generally it is known as F-bound polymorphism , and it is a form of F -bounded quantification .
A class template provides a specification for generating classes based on parameters. Class templates are generally used to implement containers. A class template is instantiated by passing a given set of types to it as template arguments. [5] The C++ Standard Library contains many class templates, in particular the containers adapted from the ...
Here, attempting to use a non-class type in a qualified name (T::foo) results in a deduction failure for f<int> because int has no nested type named foo, but the program is well-formed because a valid function remains in the set of candidate functions.
Class templates are really meta-classes: they are partial abstract data types that provide instructions to the compiler on how to create classes with the proper data members. For example, the C++ standard containers are class templates. When a programmer uses a vector, one instantiates it with a specific data type, for example, int, string or ...
(Note that if value_type were an incomplete template instance, ADL would trigger its complete instantiation.) The Barton–Nackman trick originally relied not on ADL but on a C++ feature called "friend name injection", in which an in-class declaration of a friend function made the function name visible in the immediately surrounding namespace ...
In object-oriented programming, the singleton pattern is software design pattern that restricts the instantiation of a class to a singular instance. It is one of the well-known "Gang of Four" design patterns , which describe how to solve recurring problems in object-oriented software. [ 1 ]
By supplying a host class combined with a set of different, canned implementations for each policy, a library or module can support an exponential number of different behavior combinations, resolved at compile time, and selected by mixing and matching the different supplied policy classes in the instantiation of the host class template ...
The C++20 standard brought C++ programmers a new tool for meta template programming, concepts. [6] Concepts allow programmers to specify requirements for the type, to make instantiation of template possible. The compiler looks for a template with the concept that has the highest requirements.