Rust by Example

6 Expressions

In Rust, almost every statement is an expression, meaning that the statement returns a value. This may not always be desired, so the output can be suppressed by ending the expression with a semicolon ;.

Blocks are expressions too, so they can be used as r-values in assignments. The last expression in the block will be assigned to the l-value. 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); }