Is it possible to load multiple versions of the same system?

[Stelian Ionescu]

Maybe, under rare circumstances. With my QA hat on, I say better
not to try.
 
 
>
> I've been reading the manual, papers, and slides on ASDF and XCVB.  As
> a frame of reference, I prefer the qualities exhibited by Racket's
> implementation of modules.  I was disappointed both to see XCVB
> bitrot, and then to see that a major ASDF overhaul would be necessary.
>
> That said, ignoring Racket/ASDF/XCVB, I'm curious about how loading
> multiple versions of the same system could possibly be implemented in
> Common Lisp (CL).  I'm sure people have thought about it, but I'm
> having a hard time finding references.  I'm afraid I've been skimming
> some of the material linked off of the ASDF and XCVB pages, so forgive
> me if I missed something.
>
> On the JVM, there's the notion of "classloader" that can be used to
> load multiple versions of the same class.  Unfortunately, the only
> approach I can imagine is to use some form of package renaming.  There
> appear to be several variations floating around [1], and the trade-
> offs aren't clear to me.
>
> If I think about how it might be done in ASDF, it seems like it would
> require a series of things:
>
> * intercept package definition to rename with version
> * :around-compile to handle some kind of per-system aliasing so code
>   doesn't have to change
> * teaching dependency resolution how to find the renamed, versioned
>   packages/systems
>
> But that's a wild guess.  And the more I think about it, I wonder what
> to do about some code that uses strings to put together a symbol - I
> don't think symbol-macrolet can help there.
>
> [1] implementation-specific package-local-nicknames, :around-compile
>     in ASDF, "pseudonyms"
>
> --
> Ian Tegebo
 
 
--
Stelian Ionescu a.k.a. fe[nl]ix
Quidquid latine dictum sit, altum videtur.
 
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