[plt-scheme] Units implementation: to access imports by indexes

> > Would it have been possible to compile units into e.g. vectors
> > and to access imports by indexes? In particular, having local aliases
> > for imports is indispensable?
> 
> You can rename imports in a unit. Does that do what you want?
> 
> E.g.
> 
>  (import (rename foo^ [bar baz]))
> 
> Renames bar to baz.

Thank you for the reply. 

But my question concerns the actual implementation of units by macros.
I have been wandering about mzlib/unit.ss in my free time, with "Writing
Hygienic Macros" held in one hand :)

Best,
Keiko