Re: [Rd] NAMESPACE Q: does import as exist?

From: Seth Falcon <sfalcon_at_fhcrc.org>
Date: Wed 08 Feb 2006 - 15:18:27 GMT

On 8 Feb 2006, murdoch@stats.uwo.ca wrote:
>>> in a NAMESPACE file. Useful-- yes. Possible-- I don't know!
>> Yes, this is along the lines of what I was thinking. An unpleasant
>> work around would be to create a translation package
>> that does something along the lines of Duncan M.'s suggestion,
>> importing, renaming, exporting.
>
> Why do you call it unpleasant?

Because other languages do this without defining an extra "package". I don't think users should have to go to that length to resolve such name issues.

> With the current mechanisms in R, that's probably what your
> ImportFromAs function would have to do. There's no way to have two
> names referring to the same function.

Do you mean: there's no way to have one name referring to two different functions?

After looking over some of the namespace code, I think what I'm asking for is possible (without creating extra packages). E.g., attaching a package with a NAMESPACE file looks like it will call attachNamespace(), which creates an empty env on the search path and then calls importIntoEnv() to fill it. ImportIntoEnv() ends up in do_importIntoEnv in envir.c. The comment there is encouraging:

    /* This function copies values of variables from one environment

       to another environment, possibly with different names.
       Promises are not forced and active bindings are preserved. */

Am I on track here that this implies that it is possible to have an importFromAs directive without change to the current underlying mechanism and that only higher level additions would be needed (not to say it would be easy).

Best,

+ seth



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