Rust: Implement fmt::Display for enum

enum_display.rs

use std::fmt;

#[derive(Copy,Clone)]
enum CellState { Dead, Alive }

impl fmt::Display for CellState {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let printable = match *self {
            CellState::Alive => 'x',
            CellState::Dead => ' ',
        };
        write!(f, "{}", printable)
    }
}