src/expression.md

# Expressions

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

```rust,editable
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:

```rust,editable
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 `()`.

```rust,editable
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);
}
```