Regarding a getting used up, the Rust compiler enforces a single-ownership principle where all values must have a single owner. If you move ownership of a to b,

Regarding a getting used up, the Rust compiler enforces a single-ownership principle where all values must have a single owner. If you move ownership of a to b, you cannot use a anymore as it no longer has ownership of the value. The only exception to the above is if a type "is Copy". This means that values of this type can be copied very cheaply, and in this case the compiler will allow you to use it multiple times, which is implemented by it being duplicated on each use. As for macros, they are nothing like C macros.