complete section 1, guessing game

guessing-game/src/main.rs

@@ -0,0 +1,61 @@
+// We import io from the standard library
+// It is like stdin stdout stderr and all that
+use std::cmp::Ordering;
+use std::io;
+
+use rand::Rng;
+
+// Main entry point of application
+fn main() {
+    // Use the println! macro to print to stdout
+    println!("Guess the number!");
+
+    let secret_number = rand::thread_rng().gen_range(1..=100);
+
+    println!("Please input your guess.");
+
+    // here we start the while ish loop
+    loop {
+        // uncomment the next line if you want to see the secret number as stdout
+        // println!("The secret number is {secret_number}");
+
+        // declare a mutable variable which is a growable empty string
+        let mut guess = String::new();
+
+        // from io in the std lib use stdin as input to app
+        // use read_line to read the input and stores it in a reference to the mutable variable guess
+        // Then expect is used as err handling, if something goes wrong, write to stderr and quit
+        // program with 1
+        io::stdin()
+            .read_line(&mut guess)
+            .expect("failed to read line");
+
+        // In rust, when converting types, you usually use the same var name, instead of doing something
+        // like let guess_int and let guess_str.
+        // here we define guess as unsigned 32 bit int, we reuse the guess variable, then we do a trim
+        // of it, because user input can contain 4\n which would cause it to fail always, as it cannot
+        // be parsed to an int. The parse step knows that it should parse it to the defined u32 data type.
+        // The expect has the result of either error or ok, and terminates the program if not valid
+        // integer.
+        // So here the expect is exchanged with match and pattern matching with the two result
+        // values, "Ok" and "Err". This is for gracefull err handling and starting the while loop
+        // again, even if you enter something invalid.
+        // Parse returns Result as mentioned above, but also "num" which is the Ok number
+        let guess: u32 = match guess.trim().parse() {
+            Ok(num) => num,
+            Err(_) => continue,
+        };
+
+        // print the user input with extrapolated guess variable in {} brackets
+        println!("You guessed: {guess}");
+
+        match guess.cmp(&secret_number) {
+            Ordering::Less => println!("Too small!"),
+            Ordering::Greater => println!("Too big!"),
+            Ordering::Equal => {
+            println!("You win!");
+                break;
+            }
+        }
+    }
+}