Programming a Guessing Game

Now that you should have everything set up and you wrote your first Hello World example in Lesma, let's build something more challenging. We'll write a guessing game together. The rules are simple, the program will generate a number between 1 and 100, and it will prompt the player to guess the number. If it's not the right number, we'll give him a hint if it's lower or higher. If the guess is correct, it will congratulate the player and exit.

Writing the game

Make a new source file called guess.les. There are quite a few functions from the standard library that we want to use. First, let's say hi to the player once he starts the game. To do that, we'll use the print function.

print("Guess the number! 🎰")

Afterwards, we would like to decide on a random number, but if we just choose a constant, it will be the same value every game, not fun. Let's use the random function. This function takes two numbers as inputs, the lower bound and the upper bound.

let secret_number = random(1, 101)

We can now focus on the game loop, and we need to ask the user for input. We will use the input function from standard library, which will prompt the user for an input, and return it to us.

while true
    let guess: str = input("Please input your guess: ")

Don't worry about the infinite loop, we'll get there. Our problem is that guess in the above example is a string, and we can't compare that in the same way we compare numbers, so we'll need to convert it to an integer.

    let guessed_number = strToInt(guess)

Now for the last part, we need to compare the player's guess to our secret number. We can do that with if and else statements.

    if guessed_number > secret_number
        print("Too big!")
    else if guessed_number < secret_number
        print("Too small")
    else
        print("You win!")
        break

Final Result

If you managed to follow along, you should have written code similar to the one below:

print("Guess the number! 🎰")

let secret_number = random(1, 101)

while true
    let guess = input("Please input your guess: ")
    let guessed_number = strToInt(guess)

    if guessed_number > secret_number
        print("Too big!")
    else if guessed_number < secret_number
        print("Too small")
    else
        print("You win!")
        break

We can run that using Lesma's CLI. Let's give it a shot and see if our game is working.

lesma run guess.les

Here's my trial against the robot.

Guess the number! 🎰
Please input your guess: 6
Too small
Please input your guess: 47
Too small
Please input your guess: 87
Too big!
Please input your guess: 66
Too small
Please input your guess: 77
Too small
Please input your guess: 80
Too small
Please input your guess: 82
Too big!
Please input your guess: 81
You win!