Racket/Beginner Student Language Code Error

Question

I am trying to animate a word letter by letter using Beginner Student Language on Racket. However, this code gives me an error "function call: expected a function after the open parenthesis, but found a part". I bolded the part that is giving me problems. Any suggestions?

(define theWord "blahlahblahblahblahbla")

(define (letterByLetter a)

(overlay ((substring theWord 0 a) 50 "red") (empty-scene 500 500)))

(animate letterByLetter)

Answer 1

This is because overlay takes two or more images as arguments. It looks like you want the first argument to be a call to text so the form should be

(text substring theWord 0 a)

However, note that animate will call letterByLetter 28 times a second in an infinite loop so will run out of letters and raise an exception! Perhaps you could compare a and (string-length theWord)...