rust-ape-example/src/bin/example3.rs

// https://doc.rust-lang.org/rust-by-example/variable_bindings.html
fn example3a() {
    let an_integer = 1u32;
    let a_boolean = true;
    let unit = ();

    // copy `an_integer` into `copied_integer`
    let copied_integer = an_integer;

    println!("An integer: {:?}", copied_integer);
    println!("A boolean: {:?}", a_boolean);
    println!("Meet the unit value: {:?}", unit);

    // The compiler warns about unused variable bindings; these warnings can
    // be silenced by prefixing the variable name with an underscore
    let _unused_variable = 3u32;

    let noisy_unused_variable = 2u32;
    // FIXME ^ Prefix with an underscore to suppress the warning
    // Please note that warnings may not be shown in a browser
}

// https://doc.rust-lang.org/rust-by-example/variable_bindings/mut.html
fn example3b() {
    let _immutable_binding = 1;
    let mut mutable_binding = 1;

    println!("Before mutation: {}", mutable_binding);

    // Ok
    mutable_binding += 1;

    println!("After mutation: {}", mutable_binding);

    // Error!
    // _immutable_binding += 1;
    // FIXME ^ Comment out this line
}

// https://doc.rust-lang.org/rust-by-example/variable_bindings/scope.html
fn example3c() {
    // This binding lives in the main function
    let long_lived_binding = 1;

    // This is a block, and has a smaller scope than the main function
    {
        // This binding only exists in this block
        let short_lived_binding = 2;

        println!("inner short: {}", short_lived_binding);
    }
    // End of the block

    // Error! `short_lived_binding` doesn't exist in this scope
    // println!("outer short: {}", short_lived_binding);
    // FIXME ^ Comment out this line

    println!("outer long: {}", long_lived_binding);
}

// https://doc.rust-lang.org/rust-by-example/variable_bindings/freeze.html
fn example3d() {
    let mut _mutable_integer = 7i32;

    {
        // Shadowing by immutable `_mutable_integer`
        let _mutable_integer = _mutable_integer;

        // Error! `_mutable_integer` is frozen in this scope
        // _mutable_integer = 50;
        // FIXME ^ Comment out this line

        // `_mutable_integer` goes out of scope
    }

    // Ok! `_mutable_integer` is not frozen in this scope
    _mutable_integer = 3;
}

pub fn main() {
    example3a();
    example3b();
    example3c();
    example3d();
}