enum-unitary 0.2.0

Trait and macro for unitary enums
Documentation 
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# `enum-unitary`

> Trait and macro for unitary enums

[Documentation](https://spearman.github.io/enum-unitary/enum_unitary/index.html)

The `EnumUnitary` trait carries a number of constraints and exposes some
methods for working with variants.

The `enum_unitary!` macro defines new enum implementing `EnumUnitary` and an
additional const function '`count`' returning the number of variants in the
enum.

## Usage

Add dependency to `Cargo.toml`:

```toml
[dependencies.enum-unitary]
version = "0.2.*"
git = "git://github.com/spearman/enum-unitary.git"
```

The `count` method generated by the invocation of `enum_unitary!` is a `const
fn`, so the `const_fn` feature must be enabled in addition to importing the
crate:

```rust
#![feature(const_fn)]

#[macro_use] extern crate enum_unitary;
```

Define a unitary enum:

```rust
enum_unitary! {
  pub enum E (EVariants) {
    A, B, C
  }
}
use enum_unitary::EnumUnitary;
use enum_unitary::num::Bounded;
assert_eq!(E::count(), 3);
assert_eq!(Into::<usize>::into (E::A), 0);
assert_eq!(Into::<usize>::into (E::A), 1);
assert_eq!(Into::<usize>::into (E::A), 2);
assert_eq!(E::min_value(), E::A);
assert_eq!(E::max_value(), E::C);
let mut i = E::iter_variants();
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!(E::A.next_variant(), Some (E::B));
assert_eq!(E::A.prev_variant(), None);
assert_eq!(E::B.next_variant(), Some (E::C));
assert_eq!(E::B.prev_variant(), Some (E::A));
assert_eq!(E::C.next_variant(), None);
assert_eq!(E::C.prev_variant(), Some (E::B));
```