Boolean not !

There are several cases when we might want to negate the value of a boolean expression.

Two are shown here, let me know if you think about more distinct cases I should include here.

examples/boolean-not/src/main.rs

fn main() {
    let strings = vec!["foo", "", "bar"];
    for string in strings {

        // negate a boolean value
        if ! string.is_empty() {
            println!("string: {}", string);
        }
    }


    // Toggle
    let mut on = true;
    println!("on: {}", on);
    on = ! on;
    println!("on: {}", on);
    on = ! on;
    println!("on: {}", on);
}

Negate a boolean value

In the first case we have a method called is_empty that will return true if the string is empty. What if we would like to check for not empty ? There is no such function but we can just negate the value returned by is_empty:

if ! string.is_empty() {

Toggle

This is a bool, a boolean value. If it was true then after this operation it will be false and if it was false then after this operation it will be true.

I use such toggle in a game where I have various modes and each one can be turned on and off separately. So each one will have such a variable.

on = ! on;