> But let me just ask: are macros absolutely essential? Yes, for two main reasons: (1) type-safe printf; (2) #[derive]. Nothing is "absolutely essential" in an

> But let me just ask: are macros absolutely essential? Yes, for two main reasons: (1) type-safe printf; (2) #[derive]. Nothing is "absolutely essential" in any Turing-complete language, of course, but printf comes pretty close. The only real alternative would have been to use the builder pattern for formatting like C++ does (i.e. the << operator), but nobody seriously proposed that as the aesthetics are really bad and setting formatting flags like precision is problematic. And without custom #[derive], you couldn't serialize types, which is pretty important in a modern language. Note that these are both cases (maybe the primary cases) in which OCaml has built-in ad-hoc solutions that feel very un-"systemsy". In OCaml, format strings are built in to the language, as are functions like PartialEq and Debug, the latter of which are implemented via magic built-in functions that call private internal reflection APIs. There was a desire to do better in Rust, as it was felt that these are the ugliest parts of OCaml, and so macros were part of Rust from the very early days.