enum-unitary

Deprecation notice: this crate is more or less deprecated as the enum-iterator and num-derive crates provide procedural macros to implement the required traits. The only thing this crate provides are Into for usize, isize, i64, and u64, which are trivial to implement. See also the num_enum crate which will safely derive Into for enums with #[repr(T)] attributes. strum and strum_macros also provide procedural macros and traits for enum iterators, variant counts, and conversions.

Trait and macro for unitary enums

Documentation

The EnumUnitary trait carries a number of constraints for primitive conversions iterating over variants of a unitary enum (i.e. enum variants do not have payloads).

The enum_unitary! macro defines a new enum implementing EnumUnitary and required traits.

Usage

For the macro to derive Sequence, the enum-iterator crate must also be added to Cargo.toml:

enum-iterator = "1.0"
enum-unitary = "0.5"

Define a unitary enum:

use enum_unitary::{enum_unitary, EnumUnitary, FromPrimitive, ToPrimitive};

enum_unitary! {
  #[derive(Debug, PartialEq)]
  pub enum E {
    A, B, C
  }
}

assert_eq!(enum_iterator::cardinality::<E>(), 3);
assert_eq!(Into::<usize>::into (E::A), 0);
assert_eq!(Into::<usize>::into (E::B), 1);
assert_eq!(Into::<usize>::into (E::C), 2);
assert_eq!(enum_iterator::first::<E>().unwrap(), E::A);
assert_eq!(enum_iterator::last::<E>().unwrap(),  E::C);
let mut i = enum_iterator::all::<E>();
assert_eq!(i.next(), Some (E::A));
assert_eq!(i.next(), Some (E::B));
assert_eq!(i.next(), Some (E::C));
assert_eq!(i.next(), None);
assert_eq!(enum_iterator::next (&E::A), Some (E::B));
assert_eq!(enum_iterator::previous (&E::A), None);
assert_eq!(enum_iterator::next (&E::B), Some (E::C));
assert_eq!(enum_iterator::previous (&E::B), Some (E::A));
assert_eq!(enum_iterator::next (&E::C), None);
assert_eq!(enum_iterator::previous (&E::C), Some (E::B));