public/subjects/macro_calculator/README.md

macro_calculator

Instructions

Create a function calculate_macros which receives a vector of Food structures and returns a json::JsonValue.

Food {
    name: <name>,
    calories: [<value_in_kJ>, <value_in_kcal>],
    fats: <fats_in_g>,
    carbs: <carbs_in_g>,
    proteins: <proteins_in_g>,
    nbr_of_portions: <portions>
}

Both values in the calories array will be strings, all other values will be f64s.

The function should return a json with the following format (Macros struct):

    "cals": <calories>,
    "carbs": <carbs>,
    "proteins": <proteins>,
    "fats": <fats>,

The number of portions should be taken into account. The values of the macros refer to one portion. All values should be floats (f64) and should be the addition of every macronutrient in the provided array (cals is the addition of every calories, fats is the addition of every fats, and so on...). Every value should be rounded to two decimal places (ex: 12.29) or one decimal place if it ends in 0 (ex: 18.90 -> 18.9).

Hint: You will need the json crate.

Expected Function

pub struct Food {
    //expected public fields
}

pub fn calculate_macros(foods: Vec<Food>) -> json::JsonValue {

}

Notions

• json crate

Usage

Here is a program to test your function:

use macro_calculator::*;

fn main(){
    let a = vec![
        Food {
            name: String::from("big mac"),
            calories: ["2133.84kJ".to_string(), "510kcal".to_string()],
            protein: 27.0,
            fats: 26.0,
            carbs: 41.0,
            nbr_of_portions: 2.0,
        },
        Food {
            name: "pizza margherita".to_string(),
            calories: ["1500.59kJ".to_string(), "358.65kcal".to_string()],
            protein: 13.89,
            fats: 11.21,
            carbs: 49.07,
            nbr_of_portions: 4.9,
        },
    ];

    println!("{:#}", calculate_macros(a));
}

And its output:

$ cargo run
{
    "cals": 2777.39,
    "carbs": 322.44,
    "proteins": 122.06,
    "fats": 106.93
}
$