Norman DeValliere <normandevalliere@earthlink.net> wrote:
+---------------
| My question regards this error for this code in MrEd-
| > (define (even-fibs n)
|     (define (next k)
|       (if (> k n)
|    nil
|    (let ((f (fib k)))
|      (if (even? f)
|   (cons f (next (+ k 1)))
|   (next (+ k 1)))))))
| define-values: illegal use (not at top-level) in: (#%define-values (next)
| (#%lambda (k) (if (> k n) nil (let ((f (fib k))) (if (even? f) (cons f (next
| (+ k 1))) (next (+ k 1)))))))
| >
+---------------

I agree that the error message is less than helpful, but your code really
is incorrect [perhaps you have a typo?].  Here's a properly-indented[*]
version of what you wrote:

	(define (even-fibs n)
	  (define (next k)
	    (if (> k n) 
	      nil 
	      (let ((f (fib k)))
		(if (even? f) 
		  (cons f (next (+ k 1))) 
		  (next (+ k 1)))))))

Do you see anything missing?

Hint #1: Where is "next" first called?

Hint #2: Look at the error message MzScheme gives to this example. Why?
         [Or equivalently, how is it like your code?]

	> (define (foo x)
	    (define (bar y)
	      (+ x y)))
	define-values: illegal use (not at top-level) in:
	  (#%define-values (bar) (#%lambda (y) ...
	> 

Hint #3: This example doesn't fail. How does it differ from the previous two?

	> (define (fact n)
	    (define (aux i p)
	      (if (<= i 2)
		p
		(aux (- i 1) (* i p))))
	    (aux n 1))
	> (fact 12)
	239500800
	> 


-Rob

[*] Well, my preferred format, at least.

-----
Rob Warnock, 8L-855		rpw3@sgi.com
Applied Networking		http://reality.sgi.com/rpw3/
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