Template Metaprogramming in C++ FAQ Interview Questions

C is a programming language widely used in various fields. Its template metaprogramming is an advanced programming technique that allows programmers to transform types and values ​​at compile time. Template metaprogramming is a widely discussed topic in C, so questions related to it are quite common in interviews. Here are some common template metaprogramming in C interview questions that you might be asked.

1. What is template metaprogramming?

Template metaprogramming is a technique for manipulating types and values ​​at compile time. It uses templates and metafunctions to generate code based on types and values ​​that can be more general and efficient than code written explicitly at runtime. Template metaprogramming allows programmers to abstract and generalize code to better support complex computational operations and data structures.

2. What is a meta-function?

Meta-functions are functions that are calculated at compile time. They are parameterized using templates to specialize the generated code at compile time. Metafunctions can take types and values ​​as arguments and return a result type or value. These functions are typically used in scenarios where programmers need to perform computations through the compiler at compile time.

3. C What is the difference between template metaprogramming and macros?

The main difference of C template metaprogramming is that it allows the programmer to read and write the complete C syntax and execute it at compile time, unlike macros which are limited to text replacement. Macros are often just imprecise text replacements, while template metaprogramming is more flexible, reliable, and type-safe.

4. Can metaprogramming and templates be used at runtime?

Can't. Template metaprogramming is evaluated at compile time, which means it can neither be used at runtime nor modify compiled code. If calculations and modifications need to be done at runtime, other techniques can be used, such as runtime type information (RTTI) and virtual functions.

5. What is SFINAE (substitution failure is undefined)?

SFINAE is the abbreviation of "Substitution failed as undefined". It is a technique for dealing with non-conforming code in template metaprogramming. The compiler may generate some errors when the programmer tries to use a specific type, but SFINAE allows the compiler to choose the least restrictive alternative up to the type.

6. How to avoid code duplication when using template classes?

Typically, programmers can avoid code duplication by using base classes. In this way, all commonalities can be placed in a base class, and then the base class can be inherited and extended accordingly according to different needs. Another approach is to use template specializations, which define different templates for different types of calculations.

7. What is a nested template class?

A nested template class is a template class defined inside other classes. These classes are typically used in scenarios where you need to define internal types in the class definition or provide some generality. Nested template classes can also embed specific instantiated types into the parent class so that they can be accessed when needed.

In short, template metaprogramming is an efficient and powerful technology in C. If you are preparing to face questions related to template metaprogramming during the interview, hopefully the answers to these questions will help you better prepare and answer the interviewer's questions.

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