public/subjects/box_it/README.md

box_it

Instructions

Create the following functions:

• transform_and_save_on_heap: which accepts a string of numbers separated by spaces. Each number may or may not have a 'k' as a suffix which represents kilograms. The function transforms those numbers into a vector of u32, and saves them in the heap using Box.

• take_value_ownership: which accepts the return value from transform_and_save_on_heap, unboxes the value, and returns it.

Expected Functions

pub fn transform_and_save_on_heap(s: String) -> Box<Vec<u32>> {

}
pub fn take_value_ownership(a: Box<Vec<u32>>) -> Vec<u32> {

}

Usage

Here is a program to test your functions

use box_it::*;

fn main() {
    let new_str = String::from("5.5k 8.9k 32");

    // creating a variable and we save it in the Heap
    let a_h = transform_and_save_on_heap(new_str);
    println!("Box value : {:?}", &a_h);
    println!("size occupied in the stack : {:?} bytes", (std::mem::size_of_val(&a_h)));

    let a_b_v = take_value_ownership(a_h);
    println!("value : {:?}", &a_b_v);
    println!("size occupied in the stack : {:?} bytes", (std::mem::size_of_val(&a_b_v)));
    // whenever the box, in this case "a_h", goes out of scope it will be deallocated, freed
}

And its output:

$ cargo run
Box value : [5500, 8900, 32]
size occupied in the stack : 8 bytes
value : [5500, 8900, 32]
size occupied in the stack : 24 bytes
$

Notions

• smart pointers
• using box