In SICP exercise 2.26 using DrScheme, why does cons return a list, instead of a pair of lists?

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Published on 2010-05-27T14:17:12Z Indexed on 2010/05/27 14:21 UTC
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In SICP exercise 2.26, this Scheme code is given:

(define x (list 1 2 3))
(define y (list 4 5 6))

Then this cons call is given:

(cons x y)

I expected a pair of lists would result, ((1 2 3) (4 5 6)) but the interpreter gives, ((1 2 3) 4 5 6) ...a list with 4 elements, the first being a list. Why is y treated differently? I've tried looking up other SICP answers for an explanation, but couldn't find something satisfactory. So could any Scheme/Lisp experts please shed some light on this aspect of cons? Thanks in advance for any insight.

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