[xiaomo]

I have write scheme programe as this:
(define line1 (list 1 2 3 4 5 6 7 8 9))
(define l '())
(do ((i 0 (+ i 3))) ((> i (length line1)))
(set! l (append l (list (list-ref line1 i)) ))
)
when I read it in fluent ,occur this error
Error: CAR: invalid argument [1]: wrong type [not a pair]
Error Object: ()
but I defined that this programe' function was completed.

Please, someone can help me?

[fox000002]

List index start at 0.

The max valid index is

 (- (length l) 1)

In your code, the error occurs when the index is 9, which exceed the max index value.

[xiaomo]

thank!
You are warm-hearted man