Rust - Vector with size defined at runtime

Question

How do you create an array, in rust, whose size is defined at run time?

Basically, how do you convert in rust the following code:

void f(int n){ return std::vector<int>(n); }

?

This is not possible in rust:

let n = 15;
let board: [int, ..n];

Note: I saw that it was impossible to do this in a simple manner, here, but I refuse to accept that such a simple thing is impossible :p

Thanks a lot!

possible duplicate of [Rust: Creating a vector with non-constant length](http://stackoverflow.com/questions/16745907/rust-creating-a-vector-with-non-constant-length) — Chris Morgan, Jan 27 '14 at 23:36
Slightly newer answers apply if you [want to create a vector of zeroes](https://stackoverflow.com/questions/29530011/creating-a-vector-of-zeros-for-a-specific-size) — Stein, Mar 03 '22 at 11:26

score 3 · Accepted Answer · edited Jun 30 '22 at 14:18

3

Never-mind, I found it the way:

let n = 15;      // number of items
let val = 17;    // value to replicate
let v = std::vec::from_elem(val, n);

edited Jun 30 '22 at 14:18

Coder

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answered Jan 27 '14 at 23:09

OlivierH

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Beware that this creates a vector of length `val` with values `n`. – Stein Mar 03 '22 at 11:39

score 0 · Answer 2 · answered Mar 03 '22 at 12:04

The proper way in modern Rust is vec![value; size].

Values are cloned, which is quite a relief compared to other languages that casually hand back a vector of references to the same object. E.g. vec![vec![]; 2] creates a vector where both elements are independent vectors, 3 vectors in total. Python's [[]] * 2 creates a vector of length 2 where both elements are (references to) the same nested vector.

Rust - Vector with size defined at runtime

2 Answers2