[racket-dev] Constructing an identifier to an unexported binding

From: Carl Eastlund (cce at ccs.neu.edu)
Date: Thu May 23 18:13:12 EDT 2013

On Thu, May 23, 2013 at 4:13 PM, Ryan Culpepper <ryanc at ccs.neu.edu> wrote:

> On 05/23/2013 01:57 AM, Eric Dobson wrote:
>> Some modules have macros which expand into identifiers that are not
>> exported, as they want to protect those bindings. TR currently has the
>> following code which allows it to generate an identifier which is
>> free-identifier=? to what would appear in the output of the macros.
>> define (make-template-identifier what where)
>>    (let ([name (module-path-index-resolve (module-path-index-join where
>> #f))])
>>      (parameterize ([current-namespace (make-empty-namespace)])
>>        (namespace-attach-module (current-namespace) ''#%kernel)
>>        (parameterize ([current-module-declare-name name])
>>          (eval `(,#'module any '#%kernel
>>                   (#%provide ,what)
>>                   (define-values (,what) #f))))
>>        (namespace-require `(for-template ,name))
>>        (namespace-syntax-introduce (datum->syntax #f what)))))
>> This turns out to be a slightly slow part of the initialization of TR.
>> Does anyone know another way to get such an identifier?
> There's another way around this issue, which is to avoid creating these
> identifiers at all. In other words, change the representation of the type
> environment to something that supports symbol+module pairs as keys in
> addition to identifiers. The easiest way to do that is to add in a hash
> table behind the current free-id-table, since the two tables would handle
> disjoint sets of identifiers.
> Ryan

I would not have thought that'd work, but apparently identifier-binding
will give one that information.  Nice going, Ryan!

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