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June 19, 2017 13:56
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ぴゅあぴゅあList
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#![feature(box_syntax)] | |
use std::rc::Rc; | |
#[derive(Debug)] | |
enum List<T: Clone> { | |
Empty, | |
Exist(Rc<Box<Node<T>>>), | |
} | |
#[derive(Debug)] | |
struct Node<T: Clone> { | |
elm: T, | |
next: Rc<List<T>>, | |
} | |
trait Stack_<T> { | |
fn new(T, Self) -> Self; | |
fn is_empty(&self) -> bool; | |
fn head(&self) -> Option<T>; | |
fn tail(&self) -> Option<&Self>; | |
fn append(&self, Self) -> Self; | |
fn update(self, u32, T) -> Self; | |
} | |
impl<T: Clone> Stack_<T> for List<T> { | |
fn new(elm: T, next: Self) -> Self { | |
List::Exist(Rc::new(box Node{ | |
elm: elm, | |
next: Rc::new(next) | |
})) | |
} | |
fn is_empty(&self) -> bool { | |
match *self { | |
List::Empty => true, | |
List::Exist(_) => false, | |
} | |
} | |
fn head(&self) -> Option<T> { | |
match self { | |
&List::Empty => None, | |
&List::Exist(ref n) => Some(n.elm.clone()) | |
} | |
} | |
fn tail(&self) -> Option<&Self> { | |
match self { | |
&List::Empty => None, | |
&List::Exist(ref n) => Some(&n.next) | |
} | |
} | |
fn append(&self, l: Self) -> Self { | |
match self { | |
&List::Empty => l, | |
&List::Exist(_) => { | |
List::Exist(Rc::new(box Node{ | |
elm: self.head().unwrap(), | |
next: Rc::new(self.tail().unwrap().append(l)) | |
})) | |
}, | |
} | |
} | |
fn update(self, i: u32, elm: T) -> Self { | |
if self.is_empty(){ | |
List::Empty | |
} else if i == 0 { | |
List::new(elm, self) | |
} else { | |
List::new(self.head().unwrap(), self.update(i-1, elm)) | |
} | |
} | |
} | |
fn main() { | |
let a = List::new(1, List::new(2, List::Empty)); | |
let b = List::new(3, List::new(4, List::Empty)); | |
let c = b.update(1, 3000); | |
println!("{:?}", a.append(c)); | |
} |
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なぜRc<Box>なんて型が生まれているんだ……