On Sun, Sep 11, 2022 at 3:32 AM Marc Nieper-Wißkirchen <
[email protected]> wrote:
> > I prefer what I've said in the document, as I don't understand all the
>> > implications of what you've written here.
>> >
>> > Brad
>>
>> Can you be more precise about what you don't understand what I have
>> written? Unless I have written nonsensical stuff (which, alas, happens
>> from time to time), I should be able to explain it.
>>
>
I think the point is that a pure (or referentially transparent) procedure
is one that does not visibly mutate (a) any location in the store and (b)
any variable that is free in its body. Thus:
(define wrapper ()
(let ((victim '(1 . 2)))
(define (pure) 46)
(define (impure-a)
(set-car! victim 32)
32)
(define (impure-b)
(set! victim #f)
(pure)
(pure)
(impure-a)
(impure-b))
