Andre van Tonder scripsit:
> The following program must print 1 and -1 even if it is compiled. Not
> having this behavior would be a changing a fundamental aspect of the nature
> of
> Scheme, namely, that procedures are first class.
>
> (define (f x) (display (g x)))
> (define g (lambda (x) x))
> (f x)
> (set! g (lambda (x) (- x)))
> (f x)
Yes, you are absolutely right. I was focused on redefinition, so I wasn't
even thinking about mutation by set!.
That makes the rule short and (I hope) sweet:
Redefinitions of variables are retroactive;
Redefinitions of macros are not.
To override this rule and inline things, one must have a
switch that makes the implementation non-conformant.
--
John Cowan [email protected] http://ccil.org/~cowan
Sound change operates regularly to produce irregularities;
analogy operates irregularly to produce regularities.
--E.H. Sturtevant, ca. 1945, probably at Yale
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