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Re: [Scheme-reports] ANN: first draft of R7RS small language available
On Sun, 24 Apr 2011, Aaron W. Hsu wrote:
> 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>
>>>> 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 for
>> (library (a)
> (export test else)
> (import (except (chezscheme) else))
> (define-syntax test
> (syntax-rules (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!.
I agree with your example, but I was referring to the case where everything was
at the top-level (no modules involved), where the behaviour is different.
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