Guessing Game Error

Questions & Answers
1

I read through most of the Racket Guide and decided to write a simple guessing game to test my understanding of Racket. It works for the most part, but once the user guesses the correct answer, I get this error message: application: not a procedure; expected a procedure that can be applied to arguments given: #<void>
Here is my code:

#lang racket

(let ([my-num (random 100)])
  (display "I'm thinking of a number between 1 and 100. Please enter your guess below.\n")
  (define (next-round num-rounds)
    (define guess (string->number (read-line)))
    (cond
      [(< guess my-num) (
                         (display "Too low, try again!\n")
                         (next-round (+ num-rounds 1)))]
      [(> guess my-num) (
                         (display "Too high, try again!\n")
                         (next-round (+ num-rounds 1)))]
      [else (display (string-append "You guessed it in " (number->string num-rounds) " guesses!"))]))
  (next-round 1))
2

This tries to call the function returned by calling display with one argument, whatever next-round returns. Since display doesn't return a function, it fails. Got to pay attention to your parenthesis and not add extraneous ones.

1 Like
3

Ah, I see - thank you