/Rust

# Trait std::ops::Shl

```#[lang = "shl"]
pub trait Shl<Rhs = Self> {
type Output;
fn shl(self, rhs: Rhs) -> Self::Output;
}```

The left shift operator `<<`. Note that because this trait is implemented for all integer types with multiple right-hand-side types, Rust's type checker has special handling for `_ << _`, setting the result type for integer operations to the type of the left-hand-side operand. This means that though `a << b` and `a.shl(b)` are one and the same from an evaluation standpoint, they are different when it comes to type inference.

## Examples

An implementation of `Shl` that lifts the `<<` operation on integers to a wrapper around `usize`.

```use std::ops::Shl;

#[derive(PartialEq, Debug)]
struct Scalar(usize);

impl Shl<Scalar> for Scalar {
type Output = Self;

fn shl(self, Scalar(rhs): Self) -> Scalar {
let Scalar(lhs) = self;
Scalar(lhs << rhs)
}
}

assert_eq!(Scalar(4) << Scalar(2), Scalar(16));```

An implementation of `Shl` that spins a vector leftward by a given amount.

```use std::ops::Shl;

#[derive(PartialEq, Debug)]
struct SpinVector<T: Clone> {
vec: Vec<T>,
}

impl<T: Clone> Shl<usize> for SpinVector<T> {
type Output = Self;

fn shl(self, rhs: usize) -> Self::Output {
// Rotate the vector by `rhs` places.
let (a, b) = self.vec.split_at(rhs);
let mut spun_vector: Vec<T> = vec![];
spun_vector.extend_from_slice(b);
spun_vector.extend_from_slice(a);
SpinVector { vec: spun_vector }
}
}

assert_eq!(SpinVector { vec: vec![0, 1, 2, 3, 4] } << 2,
SpinVector { vec: vec![2, 3, 4, 0, 1] });```

## Associated Types

### `type Output`

The resulting type after applying the `<<` operator.

## Required methods

### `fn shl(self, rhs: Rhs) -> Self::Output`

Performs the `<<` operation.