Re: [Scheme-reports] Formal Comment: clarify library loading rules

[Richard Kelsey <kelsey@x>]

   Date: Sun, 01 Jul 2012 19:04:37 -0400
   From: Aaron W. Hsu <arcfide@x>

   John Cowan <cowan@x> wrote:

   > Richard Kelsey scripsit:
   >> Regardless of the number of times that a library is loaded, 
   >> each program or library that imports bindings from a library
   >> will receive bindings from a single loading of that library, 
   >> of the number of the number of import or cond-expand forms
   >> in which it appears.
   >
   > This is a substantive change, so ballot ticket #441 filed.

   I would like to point out that this is incompatible with existing 
   practice on Scheme implementations which instantiate a unique 
   library instance for every phase of expansion. Putting this 
   requirement into WG1 would preclude WG2 from considering or 
   allowing library systems which use multiple instantiation semantics 
   for libraries. 

Right.  I withdraw my suggestion of the above text.

What I was trying to do was to make it possible to import the same
binding, from the same instantiation, under multiple names.  A more
direct way to do this would be to add

 (alias <import set> (<identifier1> <identifier2>) ...)

which makes the binding of <identifier1> available as both <identifier1>
and <identifier2>.

As a side note this would make

 (rename <import set> (<identifier1> <identifier2>) ...)

equivalent to

 (drop (alias <import set> (<identifier1> <identifier2>) ...)
       <identifier1> ...)

                                       -Richard Kelsey

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