## traits
### Instructions
Imagine you are designing a new video game, and your next feature is to create food that the players can eat to gain strength.
There are two types of food for now:
- `Fruit` : increases the strength by 4 units for each kilogram of fruit consumed.
- `Meat` : has a weight in kilograms, and it's pure fat content as a decimal fraction. The remaining weight of meat which is not pure fat is considered to be protein. Each kilogram of protein increases the strength by 4 units. Each kilogram of fat increases the strength by 9 units.
Define the `Food` trait for `Fruit` and `Meat` . The required method `gives` returns the amount of strength that the food provides.
Implement the `std::fmt::Display` trait for the `Player` structure, so that when `{}` corresponds to a `Player` insider a `println!` macro, it will print 3 lines:
- First: the name of the player.
- Second: strength, score and the money.
- Third: The player's list of weapons.
### Expected Functions and Structures
```rust
#[derive(Debug)]
pub struct Player {
pub name: String,
pub strength: f64,
pub score: i32,
pub money: i32,
pub weapons: Vec< String > ,
}
pub struct Fruit {
pub weight_in_kg: f64,
}
pub struct Meat {
pub weight_in_kg: f64,
pub fat_content: f64,
}
impl Player {
fn eat(& mut self, food: T) {
self.strength += food.gives();
}
}
pub trait Food {
fn gives(& self) -> f64;
}
impl Food for Fruit {
}
impl Food for Meat {
}
```
### Usage
Here is a program to test your functions and traits.
```rust
use traits::*;
fn main() {
let apple = Fruit { weight_in_kg: 1.0 };
println!("this apple gives {} units of strength", apple.gives());
let steak = Meat {
weight_in_kg: 1.0,
fat_content: 1.0,
};
let mut player1 = Player {
name: String::from("player1"),
strength: 1.0,
score: 0,
money: 0,
weapons: vec![String::from("knife")],
};
println!("Before eating {:?}", player1);
player1.eat(apple);
println!("After eating an apple\n{}", player1);
player1.eat(steak);
println!("After eating a steak\n{}", player1);
}
```
And its output:
```console
$ cargo run
this apple gives 4 units of strength
Before eating Player { name: "player1", strength: 1.0, score: 0, money: 0, weapons: ["knife"] }
After eating an apple
player1
Strength: 5, Score: 0, Money: 0
Weapons: ["knife"]
After eating a steak
player1
Strength: 14, Score: 0, Money: 0
Weapons: ["knife"]
$
```
### Notions
- [Traits ](https://doc.rust-lang.org/book/ch10-02-traits.html )
