TMP is a purely sub-language. Because the compiler cannot "change" a value once it is defined during a build, you don't use loops or variables. Instead, you use: Recursion: To mimic loops.
Concepts are the modern evolution of TMP. Instead of relying on complex SFINAE "hacks" to restrict templates, allow you to explicitly define requirements for template arguments using the requires keyword. This makes error messages much more readable and the code intent clearer. 6. Variable Templates and constexpr C Template Metaprogramming Concepts
To handle "base cases" (the exit condition for recursion). TMP is a purely sub-language
Uses a using alias or typedef to return a new type (e.g., removing a const qualifier). 3. SFINAE (Substitution Failure Is Not An Error) Concepts are the modern evolution of TMP
The primary goal of TMP is . By moving logic to the compilation phase, the final executable is smaller and faster because the work has already been done by the compiler before the user ever runs the program.
In standard C++, a function takes values and returns a value. In TMP, a takes types or constants and "returns" a new type or constant.