Building a Project (Capstone) in Racket | Schema Programming Part 10

Congratulations! You've learned about lists, recursion, macros, and modules. Now, let's combine these skills into a functional implementation of a classic game: Guess the Number.

The Goal

The program will:

1. Pick a random number between 1 and 100.
2. Ask the user for a guess.
3. Give feedback ("Too high", "Too low").
4. Track the number of guesses.
5. End when the user wins.

The Implementation

We'll define a recursive game loop that carries the state (target number and guess count).

#lang racket

(define (start-game)
  (displayln "Welcome to the Guess the Number Game!")
  (displayln "I'm thinking of a number between 1 and 100.")
  (game-loop (random 1 101) 1))

(define (game-loop target guesses)
  (printf "\nGuess #~a: " guesses)
  (define input (read))
  
  (cond
    [(not (number? input))
     (displayln "Please enter a valid number.")
     (game-loop target guesses)]
    
    [(= input target)
     (printf "Correct! You won in ~a guesses.\n" guesses)]
    
    [(< input target)
     (displayln "Too low!")
     (game-loop target (add1 guesses))]
    
    [(> input target)
     (displayln "Too high!")
     (game-loop target (add1 guesses))]))

; Start!
(start-game)

Breakdown

1. start-game: Initializes the game by picking a random number and calling the loop with the initial state (count = 1).
2. Recursion as Loop: game-loop calls itself to continue the game. This is our "while loop".
3. cond: Handles the game logic (Win vs Low vs High).
4. Immutability: We don't change a global guesses variable; we pass the new count (add1 guesses) to the next iteration.

Extensions

To practice further, try adding these features:

• Difficulty Levels: Let the user pick Easy (1-50) or Hard (1-1000).
• Save High Score: Write the best score to a file using I/O.
• GUI: Use racket/gui to make a windowed version.

Course Conclusion

Thank you for following this series on Scheme and Racket programming! You now possess a solid foundation in functional programming. Racket is a deep forest with many more paths to explore—web servers, language design, logic programming, and more.

Keep coding, and happy hacking!

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