[racket] confusion about shadowing predefined functions in interactions window

I forgot to add one rationale for having a context dependent meaning
of define-values. With the current setup, you can write

(module foo some-lang
   (define (range ...) ...))

without worrying about whether range is defined in some-lang or not.

-- 
Jens Axel Søgaard


2012/10/23 Jens Axel Søgaard <jensaxel at soegaard.net>:
> 2012/10/23 Dan Grossman <djg at cs.washington.edu>:
>>
>> Thanks, David.  I would be interested in someone walking through how this
>> behavior arises -- as well as the design issue regarding the "hopeless
>> top-level": Is this the least-bad option available or an unexpected
>> consequence?
>>
>> --Dan
>
> The expansion in the repl is:
>
>> (syntax->datum
>    (expand
>     '(define (range lo)
>        (lambda (hi) (if (> lo hi) null (cons lo ((range (+ 1 lo)) hi)))))))
>
> '(define-values
>   (range)
>   (lambda (lo)
>      (lambda (hi)
>         (if (#%app > lo hi)
>             null
>              (#%app cons lo (#%app (#%app range (#%app + '1 lo)) hi))))))
>
> The tricky thing here is that the meaning of a define-values form is
> dependent on context:
>
>     In an internal-definition context (see Internal Definitions), a
> define-values form
>     introduces local bindings.
>
>    At the top level, the top-level binding for each id is created
> after evaluating expr,
>    if it does not exist already, and the top-level mapping of each id
>    (in the namespace linked with the compiled definition) is set to the binding
>    at the same time.
>
> An the documentation on an internal-definition context says:
>
>     A define-values form: The lexical context of all syntax objects
> for the body
>     sequence is immediately enriched with bindings for the define-values form.
>
> http://docs.racket-lang.org/reference/define.html?q=define-values&q=repl#(form._((quote._~23~25kernel)._define-values))
>
> --
> Jens Axel Søgaard
>
>
> --
> --
> Jens Axel Søgaard



-- 
--
Jens Axel Søgaard