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

From: Ryan Culpepper (ryanc at ccs.neu.edu)
Date: Thu May 23 16:13:21 EDT 2013

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.


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