Two dimensional vectors in Rust

Question

Editor's note: This question predates Rust 0.1 (tagged 2013-07-03) and is not syntactically valid Rust 1.0 code. Answers may still contain valuable information.

Does anyone know how to create mutable two-dimensional vectors in Rust and pass them to a function to be manipulated?

This is what I tried so far:

extern crate std;

fn promeni(rec: &[u8]) {
    rec[0][1] = 0x01u8;
}

fn main() {
    let mut rec = ~[[0x00u8,0x00u8],
        [0x00u8,0x00u8]
    ];
    io::println(u8::str(rec[0][1]));
    promeni(rec);
    io::println(u8::str(rec[0][1]));
}

Answer 1

Did you intend that all of the subarrays will have the length 2, as in this example? In that case, the type of the parameter should not be &[u8], which is a borrowed array of u8's, but rather &[[u8; 2]].

Answer 2

You could use the macro vec! to create 2d vectors.

fn test(vec: &mut Vec<Vec<char>>){
    vec[0][0] = 'd';
    ..//
    vec[23][79] = 'd';
}

fn main() {

    let mut vec = vec![vec!['#'; 80]; 24];

    test(&mut vec);
}

Answer 3

If the functions that is going to manipulate are yours, you can create a custom struct with the helper methods to treat the vector as 2d:

use std::fmt;

#[derive(Debug)]
pub struct Vec2d<T> {
    vec: Vec<T>,
    row: usize,
    col: usize,
}

impl<T> Vec2d<T> {
    pub fn new(vec: Vec<T>, row: usize, col: usize) -> Self {
        assert!(vec.len() == row * col);
        Self { vec, row, col }
    }

    pub fn row(&self, row: usize) -> &[T] {
        let i = self.col * row;
        &self.vec[i..(i + self.col)]
    }

    pub fn index(&self, row: usize, col: usize) -> &T {
        let i = self.col * row;
        &self.vec[i + col]
    }

    pub fn index_mut(&mut self, row: usize, col: usize) -> &mut T {
        let i = self.col * row;
        &mut self.vec[i + col]
    }
}

impl<T: std::fmt::Debug> std::fmt::Display for Vec2d<T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let mut str = String::new();
        for i in 0..self.row {
            if i != 0 {
                str.push_str(", ");
            }
            str.push_str(&format!("{:?}", &self.row(i)));
        }
        write!(f, "[{}]", str)
    }
}

fn main() {
    let mut mv = Vec2d::new(vec![1, 2, 3, 4, 5, 6], 2, 3);
    *mv.index_mut(1, 2) = 10;
    println!("Display: {}", mv);
    println!("Debug: {:?}", mv);
}

The associated function new creates the Vec2d, have two main methods (index and index_mut, so you can get a index value borrowed immut ou mut) and added a Display trait to visualise it better (but it is stored as Vec<>).

Answer 4

Using type annotation

let mut vec: Vec<Vec<i32>> = Vec::new();