[plt-scheme] Version incompatibilities in PLaneT packages

From: Robby Findler (robby at cs.uchicago.edu)
Date: Tue Mar 21 16:38:32 EST 2006

PLaneT could indeed act as you want, but early on Jacob and I decided
to outlaw this one and see how often it came up (this is the first
report we're hearing, FWIW).

The danger is that there is some state (often this state is in the form
of define-structs created multiple times but it could be anything) in
the module that flows from one of the instances of the module back to
the other one. Without planet, this cannot happen and we didn't want to
introduce this possibility.

Possibly this could be relaxed to only a single instance per major
version number, instead of a single instance ever.


At Tue, 21 Mar 2006 16:31:42 -0500, "Carl Eastlund" wrote:
> DrScheme gave me this error today while I tried to run some code:
> Package contract-utils.plt loaded twice with multiple versions:
> attempted to load version 1.3 while version 2.0 was already loaded
> Why is this an error?  I'd much rather have different versions of the
> same planet library be considered wholly different modules, so they
> could load together without complaint.  As it stands, I can fix this
> problem, but only by editing multiple files, which I may just have to
> do again the next time there's an upgrade.  This would be even worse
> if other planet modules caused this problem.  If I loaded
> "alices-code.plt" and "bobs-code.plt", and Alice used
> contract-utils.plt version 1.3 and Bob used contract-utils.plt version
> 2.0, I'm out of luck.  I cannot fix that bug, yet it seems to me that
> code should just run.
> Can anyone clarify the situation for me?
> --
> Carl Eastlund
> "Cynical, but technically correct."
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