Macro def 

macro_rules! def {
    ($name:ident; $(fn ($($arg:ident : $type:ty),* $(,)?) $(-> $ret:ty)? $body:block);+ $(;)?) => { ... };
    (pub $name:ident; $(fn ($($arg:ident : $type:ty),* $(,)?) $(-> $ret:ty)? $body:block);+ $(;)?) => { ... };
}