


Why Must Non-Type Template Parameters Be Constant Integral Expressions?
Dec 15, 2024 pm 10:37 PMNon-Type Template Parameters and Constant Integral Expressions
Non-type template parameters are a valuable tool for customizing templates but why is it crucial that they be constant integral expressions?
Consider the following code:
template <std::string temp> void foo() { // ... }
Compiling this code yields the error:
error C2993: 'std::string' : illegal type for non-type template parameter 'temp'.
Non-type template parameters must be constant integral expressions as they are evaluated during compilation. This allows for direct code generation without runtime evaluation. Types like std::string, which can change at runtime, cannot be substituted during compile-time.
The standard dictates that non-type template parameters can only be the following types:
- Integral or enumeration types
- Pointers to objects or functions
- Lvalue references to objects or functions
- Pointers to members
- std::nullptr_t
By restricting non-type template parameters to compile-time constant values, the compiler can generate efficient code at compile-time, ensuring that the program's behavior can be fully determined and optimized ahead of runtime.
The above is the detailed content of Why Must Non-Type Template Parameters Be Constant Integral Expressions?. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undress AI Tool
Undress images for free

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Clothoff.io
AI clothes remover

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

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

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.

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.

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

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.

People who study Python transfer to C The most direct confusion is: Why can't you write like Python? Because C, although the syntax is more complex, provides underlying control capabilities and performance advantages. 1. In terms of syntax structure, C uses curly braces {} instead of indentation to organize code blocks, and variable types must be explicitly declared; 2. In terms of type system and memory management, C does not have an automatic garbage collection mechanism, and needs to manually manage memory and pay attention to releasing resources. RAII technology can assist resource management; 3. In functions and class definitions, C needs to explicitly access modifiers, constructors and destructors, and supports advanced functions such as operator overloading; 4. In terms of standard libraries, STL provides powerful containers and algorithms, but needs to adapt to generic programming ideas; 5

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

C polymorphismisuniqueduetoitscombinationofcompile-timeandruntimepolymorphism,allowingforbothefficiencyandflexibility.Toharnessitspowerstylishly:1)Usesmartpointerslikestd::unique_ptrformemorymanagement,2)Ensurebaseclasseshavevirtualdestructors,3)Emp
