Trait LenMut

pub trait LenMut: Default + Clear {
    // Required methods
    fn truncate(&mut self, len: usize);
    fn split_off(&mut self, index: usize) -> Self;
}

A trait for modifying the length of a collection.

These methods must take at most a linear amount of time and space with respect to the number of elements which are moved or dropped.

Required Methods

fn truncate(&mut self, len: usize)

Truncates the collection to be no greater than len long, dropping elements as needed.

If the collection is less than len long, do nothing.

Panics

Panics if len is not valid according to the collection. For example, the implementation for String will panic if len does not lie on a character boundary.

Examples

use len_trait::LenMut;

fn check_truncate<C: LenMut>(mut collection: C) {
    let old_len = collection.len();
    collection.truncate(5);
    if old_len >= 5 {
        assert_eq!(collection.len(), 5);
    } else {
        assert_eq!(collection.len(), old_len);
    }
}

check_truncate("Hello, world!".to_string());
check_truncate(vec![1, 2, 3]);

fn split_off(&mut self, index: usize) -> Self

Splits off the collection at the given index, returning the data past the index.

Panics

Panics if index > len.

Examples

use len_trait::LenMut;

fn check_split_off<C: LenMut>(mut collection: C) {
    let old_len = collection.len();
    let split = collection.split_off(5);
    assert_eq!(collection.len(), 5);
    assert_eq!(split.len(), old_len - 5);
}

check_split_off("Hello, world!".to_string());
check_split_off(vec![1, 2, 3, 4, 5, 6, 7, 8, 9]);

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl LenMut for String

fn truncate(&mut self, len: usize)

fn split_off(&mut self, index: usize) -> Self

impl<T> LenMut for VecDeque<T>

fn truncate(&mut self, len: usize)

fn split_off(&mut self, index: usize) -> Self

impl<T> LenMut for Vec<T>

fn truncate(&mut self, len: usize)

fn split_off(&mut self, index: usize) -> Self

Implementors