Struct Doubling 

pub struct Doubling<V> { /* private fields */ }

ダブリング

Examples

use doubling::{Doubling, Transition, Value};

#[derive(Debug, PartialEq)]
struct Sum(i64);

impl Value for Sum {
    fn op(&self, other: &Self) -> Self {
        Sum(self.0 + other.0)
    }
}

struct E {
    to: usize,
    value: i64,
}

// 0, 1, 2, 0, 1, 2, ...
let n = 3;
let to = vec![
    E { to: 1, value: 1 },
    E { to: 2, value: 10 },
    E { to: 0, value: 100 },
];
let doubling = Doubling::new(n, 100, |i| {
    let e = &to[i];
    Transition::new(e.to, Sum(e.value))
});

assert_eq!(
    doubling.fold(0, 4, Sum(0), |acc, t| Sum(acc.0 + t.value.0)),
    // 0 -> 1 -> 2 -> 0 -> 1
    Sum(1 + 10 + 100 + 1)
);

Implementations

impl<V> Doubling<V>

where V: Value,

pub fn new<F>(n_state: usize, max_steps: usize, step1: F) -> Self

where F: Fn(usize) -> Transition<V>,

ダブリングのテーブルを構築します。

step1(i)は状態iから1回の遷移における

• 遷移先の状態
• その遷移にともなう値

を返す関数。

pub fn get(&self, start: usize, k: usize) -> &Transition<V>

状態startから長さpow(2, k)の遷移を返します。

pub fn fold<A, F>(&self, start: usize, step: usize, init: A, f: F) -> A

where F: FnMut(A, &Transition<V>) -> A,

状態startからstep回の遷移、初期値initから始めてfで畳みこんだ結果を返します。

Trait Implementations

impl<V: Clone> Clone for Doubling<V>

fn clone(&self) -> Doubling<V>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<V: Debug> Debug for Doubling<V>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.