Generic stack
- Rust course
- Intermediate
- Lesson 112/115
- 7 min
Build a Vec-backed generic Stack<T> data structure.
Final task: generic stack
In the intermediate level's final tasks you'll combine generics, traits, iterators and error handling. The first: a stack that works with any type. Last in, first out (LIFO):
struct Yigin<T> {
ogeler: Vec<T>,
}
impl<T> Yigin<T> {
fn new() -> Self { .. }
fn push(&mut self, x: T) { .. }
fn pop(&mut self) -> Option<T> { .. } // None if empty
fn peek(&self) -> Option<&T> { .. } // look without removing
fn len(&self) -> usize { .. }
fn is_empty(&self) -> bool { .. }
}peek returns a reference, so T doesn't need to be Clone.
Delegating to Vec
Stack behaviour matches Vec's methods one to one; the wrapper only narrows the API and gives meaningful names:
impl<T> Yigin<T> {
fn push(&mut self, x: T) { self.ogeler.push(x); }
fn pop(&mut self) -> Option<T> { self.ogeler.pop() }
fn peek(&self) -> Option<&T> { self.ogeler.last() }
}The user can't insert into the middle of the vector; the stack's invariants are protected.
Practice Stack
Write the Yigin<T> type above with all its methods. Push 1, 2, 3; print the results of pop(), peek(), len() and is_empty() for an empty Yigin<&str> on one line.
Starter code
fn main() {
// buraya yaz
}Sample solution
struct Yigin<T> {
ogeler: Vec<T>,
}
impl<T> Yigin<T> {
fn new() -> Self {
Self { ogeler: Vec::new() }
}
fn push(&mut self, x: T) {
self.ogeler.push(x);
}
fn pop(&mut self) -> Option<T> {
self.ogeler.pop()
}
fn peek(&self) -> Option<&T> {
self.ogeler.last()
}
fn len(&self) -> usize {
self.ogeler.len()
}
fn is_empty(&self) -> bool {
self.ogeler.is_empty()
}
}
fn main() {
let mut y = Yigin::new();
for n in [1, 2, 3] {
y.push(n);
}
let p = y.pop();
let t = y.peek().copied();
let bos: Yigin<&str> = Yigin::new();
println!("{:?} {:?} {} {}", p, t, y.len(), bos.is_empty());
}Expected output
Some(3) Some(2) 2 true
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Which <code>Vec</code> method is used for <code>peek</code>?
- get(0)
- last() Correct answer
- first()
- pop()
Explanation: The top of the stack is the end of the vector; last() gives Option<&T> to the last element.
2 Look at the top
fn peek(&self) -> Option<&T> {
self.ogeler.____()
}fn peek(&self) -> Option<&T> {
self.ogeler.last()
}Explanation: last gives a reference to the last element.
3 Operation and result (1, 2, 3 pushed)
| Term | Meaning |
|---|---|
pop() |
Some(3) |
then peek() |
Some(2) |
then len() |
2 |
Yigin::<&str>::new().is_empty() |
true |