Tracking Issue for Vec::from_elem and Vec::from_elem_in #164215

Feature gate: #![feature(vec_from_elem)]

This is a tracking issue for Vec::from_elem and Vec::from_elem_in.

These two methods allow creating a Vec that contains a specific element n times. The element must implement Clone for this. Internally, the methods can make use of specialization to make this operation more efficient than Vec::new followed by Vec::resize, for example when the element is zero, which will result in a single call to calloc instead of malloc + memset.

Public API

impl <T: Clone> Vec<T, Global> {
    pub fn from_elem(elem: T, n: usize) -> Self;
}

impl <T: Clone, A: Allocator> Vec<T, A> {
    pub fn from_elem_in(elem: T, n: usize, alloc: A) -> Self;
}

Steps / History

(Remember to update the S-tracking-* label when checking boxes.)

• ACP:
• Implementation: alloc: Unstably add Vec::from_elem and Vec::from_elem_in #164043
• Final comment period (FCP)¹
• Stabilization PR

Unresolved Questions

• None yet.