# Generics

### Functions

1. 🌟🌟🌟
``````
// Fill in the blanks to make it work
struct A;          // Concrete type `A`.
struct S(A);       // Concrete type `S`.
struct SGen<T>(T); // Generic type `SGen`.

fn reg_fn(_s: S) {}

fn gen_spec_t(_s: SGen<A>) {}

fn gen_spec_i32(_s: SGen<i32>) {}

fn generic<T>(_s: SGen<T>) {}

fn main() {
// Using the non-generic functions
reg_fn(__);          // Concrete type.
gen_spec_t(__);   // Implicitly specified type parameter `A`.
gen_spec_i32(__); // Implicitly specified type parameter `i32`.

// Explicitly specified type parameter `char` to `generic()`.
generic::<char>(__);

// Implicitly specified type parameter `char` to `generic()`.
generic(__);

println!("Success!");
}
``````
1. 🌟🌟 A function call with explicitly specified type parameters looks like: `fun::<A, B, ...>()`.
``````
// Implement the generic function below.
fn sum

fn main() {
assert_eq!(5, sum(2i8, 3i8));
assert_eq!(50, sum(20, 30));
assert_eq!(2.46, sum(1.23, 1.23));

println!("Success!");
}
``````

### Struct and `impl`

1. 🌟
``````
// Implement struct Point to make it work.

fn main() {
let integer = Point { x: 5, y: 10 };
let float = Point { x: 1.0, y: 4.0 };

println!("Success!");
}
``````
1. 🌟🌟
``````
// Modify this struct to make the code work
struct Point<T> {
x: T,
y: T,
}

fn main() {
// DON'T modify this code.
let p = Point{x: 5, y : "hello".to_string()};

println!("Success!");
}
``````
1. 🌟🌟
``````
// Add generic for Val to make the code work, DON'T modify the code in `main`.
struct Val {
val: f64,
}

impl Val {
fn value(&self) -> &f64 {
&self.val
}
}

fn main() {
let x = Val{ val: 3.0 };
let y = Val{ val: "hello".to_string()};
println!("{}, {}", x.value(), y.value());
}
``````

### Method

1. 🌟🌟🌟
``````struct Point<T, U> {
x: T,
y: U,
}

impl<T, U> Point<T, U> {
// Implement mixup to make it work, DON'T modify other code.
fn mixup
}

fn main() {
let p1 = Point { x: 5, y: 10 };
let p2 = Point { x: "Hello", y: '中'};

let p3 = p1.mixup(p2);

assert_eq!(p3.x, 5);
assert_eq!(p3.y, '中');

println!("Success!");
}
``````
1. 🌟🌟
``````
// Fix the errors to make the code work.
struct Point<T> {
x: T,
y: T,
}

impl Point<f32> {
fn distance_from_origin(&self) -> f32 {
(self.x.powi(2) + self.y.powi(2)).sqrt()
}
}

fn main() {
let p = Point{x: 5, y: 10};
println!("{}",p.distance_from_origin());
}
``````

You can find the solutions here(under the solutions path), but only use it when you need it