Generic programming and template metaprogramming are two powerful techniques in modern C++ for processing different types of data at runtime (generic programming) and creating and evaluating code at compile time (template metaprogramming). Although they are both based on templates, they are very different in functionality and usage. In practice, the two techniques are often used together, for example, generic code can be combined with template metaprogramming to create and instantiate data structures at runtime.

C++ is a powerful programming language, but in practice, sometimes a lot of redundant code appears. In order to improve code reusability, C++ introduced template metaprogramming (TemplateMetaprogramming). This is a technique that leverages the compiler's template mechanism for efficient metaprogramming. This article will introduce the basic concepts and application scenarios of template metaprogramming, and how to use it to build an efficient code base. Macroscopically speaking, C++ template metaprogramming encapsulates common programming patterns, algorithms, data structures, etc.

The relationship between the function parameter passing method and template metaprogramming: value passing: copying the parameter value, the function cannot modify the original variable. Pass by reference: Pass a reference to the parameter, and the function can modify the original variable. Pointer passing: passing a pointer to a parameter, the function can modify the original variable by dereferencing the pointer. Template metaprogramming can generate different codes based on parameter types by specifying the parameter passing method.

C++ static functions can be used in template metaprogramming for: Constant evaluation type conversion code generation For example, static functions can be used to calculate compile-time constants, such as array lengths, to avoid runtime calculation overhead.

C templates are used to implement generic programming, allowing for the writing of general code. 1) Define template functions, such as max functions, which are suitable for any type. 2) Create template classes, such as general container classes. 3) Pay attention to template instantiation, compilation time, template specialization, debugging and error information. 4) Follow best practices, keep the code simple, and consider using constraint template parameters.

Memory optimization techniques based on template metaprogramming in C++ are implemented in the following ways: Code generation: dynamically generate code at compile time to avoid allocating memory at runtime. Meta-functions: perform calculations at compile time and generate optimized code. Practical case: Array pool avoids the overhead of multiple allocations by sharing array memory.

The advantages of C++ template metaprogramming (TMP) in server architecture include: Performance optimization: The generated code has no runtime overhead because it is generated at compile time. High maintainability: Makes code more modular and reusable, allowing dynamic code generation based on type information. Code Generation: Can be used to generate complex code that is difficult to write manually.

C 20Concepts is a mechanism for imposing constraints on template parameters to clarify the conditions that a specified type must meet. By limiting the template parameter type, it makes template programming clearer and easier to maintain, and improves the readability of compile error information. For example, std::integral restricts the template parameters to integers; users can also customize Concept, such as Addable check whether the type supports addition operations. Its common uses include: 1. Simplify template code and avoid SFINAE writing; 2. Improve code readability; 3. Improve compilation error prompts; 4. Build a safe generic library. When using it, multiple Concepts can be combined and default implementations can be provided, but over-design should be avoided. It is recommended to add approximately after the logic is stable.