Add example of guessing game with custom type for validation

guessing_game_ng/src/main.rs

@@ -0,0 +1,58 @@
+use std::io;
+use std::cmp::Ordering;
+use rand::Rng;
+
+const MIN_NUMBER: i32 = 1;
+const MAX_NUMBER: i32 = 100;
+
+pub struct Guess {
+    value: i32,
+}
+
+impl Guess {
+    pub fn new(value: i32) -> Guess {
+        if value < MIN_NUMBER || value > MAX_NUMBER {
+            panic!("Guess value must be between 1 and 100, got {}.", value);
+        }
+
+        Guess { value }
+    }
+
+    pub fn value(&self) -> i32 {
+        self.value
+    }
+}
+
+fn main() {
+    let secret_number = rand::thread_rng().gen_range(MIN_NUMBER, MAX_NUMBER + 1);
+
+    println!("Guess the number between [{}, {}] {}", MIN_NUMBER, MAX_NUMBER, secret_number);
+
+    loop {
+        let mut guess = String::new();
+        println!("Input guess:");
+        io::stdin().read_line(&mut guess).expect("Failed to read line");
+
+        let guess: i32 = match guess.trim().parse() {
+	    Ok(num) => num,
+	    Err(_) => {
+	        println!("That ain't a number!");
+		continue;
+	    }
+	};
+
+        let guess: Guess = Guess::new(guess);
+
+        println!("You guessed: {}", guess.value);
+
+        match guess.value.cmp(&secret_number) {
+            Ordering::Less => println!("Too small!"),
+            Ordering::Greater => println!("Too big!"),
+            Ordering::Equal => {
+                println!("Congrats, you did it!");
+                break;
+            }
+        }
+    }
+
+}