It isn't redefined, it is shadowed-- the definitions in a module are
in one lexical scope lower than the module position. Racket's module
system doesn't allow redefinition.
That is, the first example has more in common with this expression
(let ([+ -])
(+ 7 2))
than it does with the second one.
The second one is more like:
(let ([+ 5]
[+ -])
...)
with two bindings introduced at the same scope.
Robby
On Tue, Jan 10, 2012 at 2:51 PM, Gustavo Massaccesi <gust...@oma.org.ar> wrote:
> I tried the following programs in DrRacket 5.2
>
> ;--- start
> #lang racket/base
> (define + -)
> (+ 7 2)
> ;--- end
> Result:
> 5
> ;---
>
>
> ;--- start
> #lang racket/base
> (require (only-in racket/base +))
> (define + -)
> (+ 7 2)
> ;--- end
> Result:
> [error] module: identifier is already imported in: +
> ;---
>
>
> In the first example the function + is redefined. I expected to get an
> error in both programs. I’m not sure if this is a bug or a feature.
>
> (And I couldn’t find in the documentation which is the expected behavior.)
>
> Gustavo
>
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