国产av日韩一区二区三区精品,成人性爱视频在线观看,国产,欧美,日韩,一区,www.成色av久久成人,2222eeee成人天堂

Home Backend Development C++ Why is Partial Class Template Argument Deduction Not Possible?

Why is Partial Class Template Argument Deduction Not Possible?

Nov 09, 2024 am 01:02 AM

Why is Partial Class Template Argument Deduction Not Possible?

Template Argument Deduction for Class Templates: Limitations and Implications

In the wake of the P0091 proposal to unify template argument deduction behavior for function and class templates, a question arises: why is partial class template argument deduction not possible?

The initial proposal aimed to align the deduction mechanisms, allowing for partial deduction in both contexts. However, concerns emerged regarding potential confusion when the deduced values produce multiple valid template specializations. A classic example is the deduction of a tuple type: by specifying only one argument, the compiler could infer a tuple with a single element, even though the original tuple definition includes multiple elements.

To prevent such ambiguity, partial class template argument deduction was removed from the proposal. This limitation affects scenarios where developers may wish to explicitly specify certain template parameters while leaving others to be deduced.

For instance, consider the following class template:

template <std::size_t S, typename T>
struct test
{
    static constexpr auto size = S;
    using type_t = T;

    test(type_t (&amp;input)[size]) : data(input) {}
    type_t (&amp;data)[size]{};
};

A helper function serves as a syntactic sugar for instantiating test objects:

template <std::size_t S, typename T>
test<S, T> helper(T (&amp;input)[S]) { return input; }

When using the helper with a pre-declared array:

int buffer[5];

auto a = helper<5, int>(buffer); // No deduction
auto b = helper<5>(buffer);      // Type deduced
auto c = helper(buffer);         // Type and size deduced

Partial deduction is not supported in the case of class templates, as evidenced by the failure of auto b = helper<5>(buffer);. The compiler cannot infer the T parameter from the argument, leading to a compilation error. Instead, auto c = helper(buffer); successfully deduces both S and T, demonstrating the necessity of specifying all template parameters explicitly.

The above is the detailed content of Why is Partial Class Template Argument Deduction Not Possible?. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undress AI Tool

Undress AI Tool

Undress images for free

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

C   Destructors code samples C Destructors code samples Jun 13, 2025 am 12:04 AM

The destructor in C is used to free the resources occupied by the object. 1) They are automatically called at the end of the object's life cycle, such as leaving scope or using delete. 2) Resource management, exception security and performance optimization should be considered during design. 3) Avoid throwing exceptions in the destructor and use RAII mode to ensure resource release. 4) Define a virtual destructor in the base class to ensure that the derived class objects are properly destroyed. 5) Performance optimization can be achieved through object pools or smart pointers. 6) Keep the destructor thread safe and concise, and focus on resource release.

C   Polymorphism : is function overloading a kind of polymorphism? C Polymorphism : is function overloading a kind of polymorphism? Jun 20, 2025 am 12:05 AM

Yes, function overloading is a polymorphic form in C, specifically compile-time polymorphism. 1. Function overload allows multiple functions with the same name but different parameter lists. 2. The compiler decides which function to call at compile time based on the provided parameters. 3. Unlike runtime polymorphism, function overloading has no extra overhead at runtime, and is simple to implement but less flexible.

What Are the Different Kinds of Polymorphism in C  ? Explained What Are the Different Kinds of Polymorphism in C ? Explained Jun 20, 2025 am 12:08 AM

C has two main polymorphic types: compile-time polymorphism and run-time polymorphism. 1. Compilation-time polymorphism is implemented through function overloading and templates, providing high efficiency but may lead to code bloating. 2. Runtime polymorphism is implemented through virtual functions and inheritance, providing flexibility but performance overhead.

How to Implement Polymorphism in C  : A Step-by-Step Tutorial How to Implement Polymorphism in C : A Step-by-Step Tutorial Jun 14, 2025 am 12:02 AM

Implementing polymorphism in C can be achieved through the following steps: 1) use inheritance and virtual functions, 2) define a base class containing virtual functions, 3) rewrite these virtual functions by derived classes, and 4) call these functions using base class pointers or references. Polymorphism allows different types of objects to be treated as objects of the same basis type, thereby improving code flexibility and maintainability.

C  : Is Polymorphism really useful? C : Is Polymorphism really useful? Jun 20, 2025 am 12:01 AM

Yes, polymorphisms in C are very useful. 1) It provides flexibility to allow easy addition of new types; 2) promotes code reuse and reduces duplication; 3) simplifies maintenance, making the code easier to expand and adapt to changes. Despite performance and memory management challenges, its advantages are particularly significant in complex systems.

C   Destructors: Common Errors C Destructors: Common Errors Jun 20, 2025 am 12:12 AM

C destructorscanleadtoseveralcommonerrors.Toavoidthem:1)Preventdoubledeletionbysettingpointerstonullptrorusingsmartpointers.2)Handleexceptionsindestructorsbycatchingandloggingthem.3)Usevirtualdestructorsinbaseclassesforproperpolymorphicdestruction.4

What Are the Various Forms of Polymorphism in C  ? What Are the Various Forms of Polymorphism in C ? Jun 20, 2025 am 12:21 AM

C polymorphismincludescompile-time,runtime,andtemplatepolymorphism.1)Compile-timepolymorphismusesfunctionandoperatoroverloadingforefficiency.2)Runtimepolymorphismemploysvirtualfunctionsforflexibility.3)Templatepolymorphismenablesgenericprogrammingfo

Polymorphism in C  : A Comprehensive Guide with Examples Polymorphism in C : A Comprehensive Guide with Examples Jun 21, 2025 am 12:11 AM

Polymorphisms in C are divided into runtime polymorphisms and compile-time polymorphisms. 1. Runtime polymorphism is implemented through virtual functions, allowing the correct method to be called dynamically at runtime. 2. Compilation-time polymorphism is implemented through function overloading and templates, providing higher performance and flexibility.

See all articles