Question

I’m using R5RS standart of Scheme language.

Please have a look at these two objects:

1. (1 (2 . 3))
2. (1 2 . 3)

Do they have the same memory representations? Like this (A):

Or the first one is different? Like this (B):

So… What is correct?

Answer 1

They’re different. The first list is constructed like this, corresponding to the “B” figure:

(cons 1
      (cons (cons 2 3)
            '()))

> '(1 (2 . 3))

Whereas the second list structure is constructed like this, which corresponds to the “A” figure:

(cons 1
      (cons 2 3))

> '(1 2 . 3)

Also notice that the second one is not a proper list (meaning: a list that ends with null).