What is template metaprogramming versus constexpr for compile-time work?

Template metaprogramming performs compile-time computation via template instantiation and specialization (functional, verbose, historically the main tool). constexpr functions let you write compile-time logic in ordinary imperative C++, which is far more readable and maintainable. Modern C++ favors constexpr/consteval for values and reserves templates for type-level work, often combining both.

// constexpr is clearer than the equivalent recursive template
constexpr int factorial(int n){ return n<=1?1:n*factorial(n-1); }