Rust by Example

Expressions

A Rust program is (mostly) made up of a series of statements:

fn main() {

// statement

// statement

// statement

}

There are a few kinds of statements in Rust. The most common two are declaring a variable binding, and using a ; with an expression:

fn main() {

// variable binding

let x = 5;

// expression;

x;

x + 1;

15;

}

Blocks are expressions too, so they can be used as values in assignments. The last expression in the block will be assigned to the place expression such as a local variable. However, if the last expression of the block ends with a semicolon, the return value will be ().

fn main() {

let x = 5u32;

let y = {

let x_squared = x * x;

let x_cube = x_squared * x;

// This expression will be assigned to `y`

x_cube + x_squared + x

};

let z = {

// The semicolon suppresses this expression and `()` is assigned to `z`

2 * x;

};

println!("x is {:?}", x);

println!("y is {:?}", y);

println!("z is {:?}", z);

}

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