Logical Operators Part 3

Part of the Fundamentals section of Coddy's Rust journey. Lesson 23 of 75.

When checking multiple conditions, the computer stops checking as soon as it knows the final answer (This is called short-circuit evaluation).

For example:

let x: i32 = 0;
let y: i32 = 5;
let result: bool = x != 0 && y / x > 2;

Here x equals 0, therefore it will not evaluate y / x > 2. If we would reverse the order:

let result: bool = y / x > 2 && x != 0;

This will result in an error because y will be divided by 0 which is illegal in math.

This technique is used to optimize the evaluation of logical expressions. For example:

let a: i32 = 0;
let b: i32 = 2;
let c: i32 = 3;
let d: i32 = 5;
let result: bool = (a > 0 && b < 2) || (c < -5 && d < 10);

In this example b < 2 and d < 10 will not be evaluated because a > 0 and c < -5 are both false.

Challenge

Beginner

Let's create a program to decide if it's a good day for solar panel energy production

Initialize these variables:

is_sunny with the value true
wind_speed with the value 5.4
temperature with the value 23
solar_panel_output with the value 9
is_cloudy with the value false

Create one logical expression that checks ALL of these conditions:

It's sunny
The wind speed is less than 10
The solar panel output is less than 15
The temperature is above 20 OR there are no clouds

Try it yourself

fn main() {
    // Initialize variables
    // Replace the placeholder values below with the ones from the task
    let is_sunny: bool = false;
    let wind_speed: f64 = 99.0;
    let temperature: i32 = 0;
    let solar_panel_output: i32 = 99;
    let is_cloudy: bool = true;
    
    // The complete logical expression
    // Replace the placeholder below with the full condition
    let result: bool = false;
    
    // Don't delete the lines below
    println!("Checking conditions for solar energy production...");
    println!("1. Is it sunny? {}", is_sunny);
    println!("2. Is wind speed safe? {}", (wind_speed < 10.0));
    println!("3. Can panels produce more? {}", (solar_panel_output < 15));
    println!("4. Is temperature good OR no clouds? {}", (temperature > 20 || !is_cloudy));
    println!("\\nFinal result - Good day for solar energy production: {}", result);
}