Macro new_type::newtype

macro_rules! newtype {
    ( $( $newtype:ident ),* ) => { ... };
}

Implements its arguments as newtypes.

The macro is meant to provide easy means to enhance the semantics of language built-ins. Newtypes come with Deref, DerefMut, AsRef, AsMut, and From traits. Further they implement almost all std::ops and std::cmp of the type they wrap. Exceptions are std::ops::{Drop, Fn, FnMut, FnOnce, Index, IndexMut, RangeBounds}.

Examples

Operations are available on newtypes:

newtype!(Count);
let count_one = Count(100);
let count_two = Count(50);
// We can add 'Count' because we can add i32!
assert_eq!(count_one + count_two, Count(150))

Functions are available on newtypes:

newtype!(Humans);
let mut some_humans = Humans(HashSet::new());
some_humans.insert("Maria");
some_humans.insert("Peter");
let mut set = HashSet::new();
set.insert("Kim");
set.insert("Mia");
// We can extend Humans with a HashSet!
some_humans.extend(set.iter());
// We can ask for '.len()' on Humans because we can ask for '.len()' on HashSet!
assert_eq!(some_humans.len(), 4)

Newtypes can be nested:

newtype!(A, B, C);
let abc_one = A(B(C(5)));
let abc_two = A(B(C(5)));
// We can add nested newtypes because we can add the wrapped type!
assert_eq!(abc_one + abc_two, A(B(C(10))))