區塊 (block) 和範疇 (scope)

區塊

A block in Rust contains a sequence of expressions, enclosed by braces {}. Each block has a value and a type, which are those of the last expression of the block:

fn main() {
    let z = 13;
    let x = {
        let y = 10;
        println!("y: {y}");
        z - y
    };
    println!("x: {x}");
}

If the last expression ends with ;, then the resulting value and type is ().

This slide and its sub-slides should take about 5 minutes.
  • 你可以藉由改變區塊中的最後一行來觀察區塊數值的變化。舉例來說，新增或刪除一個分號，或者使用 return。