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Re: [Scheme-reports] ANN: first draft of R7RS small language available
On Sun, 24 Apr 2011 15:50:15 -0400, Andre van Tonder <andre@x>
> On Sun, 24 Apr 2011, Aaron W. Hsu wrote:
>> On Sun, 24 Apr 2011 15:34:23 -0400, Andre van Tonder
>> <andre@x> wrote:
>>> The latter behaviour may be compatible with the document in systems in
>>> which all identifiers are considered implicitly bound at toplevel, so
>>> the DEFINE would be like a SET!
>> Even in systems where this is the case, and Chez in particular, this
>> does not do this.
> I thinkthe reason Chez does not doi this is becasue you are replacing a
> syntactic binding for ELSE by a variable binding, so the DEFINE is not
> like a SET!. IF the original binding of ELSE was a variable binding,
> the define would be like a SET! and the ELSE clause would match.
It does not matter whether the else is a syntactic binding or a variable
binding. Chez behaves the same in either case regarding this. Take this
> (library (a)
(export test else)
(import (except (chezscheme) else))
[(_ else) 'else] [(_ blah) #f]))
(define else #f))
> (import (a))
> (test else)
> (test x)
> (define else #t)
> (test else)
The definition actually alters the lexical binding; library exports are
immutable, and thus a redefinition is more like a shadowing than a set!.
Aaron W. Hsu
Programming is just another word for the lost art of thinking.
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