[Agda] hints on switching between Agda versions

[Martin Escardo]

On 17/11/16 20:38, Andrew Pitts wrote:
> I wonder too. But I wonder more why installing into a fresh sandbox is
> causing any package to be reinstalled at all. However, such
> cabal-related questions are probably not for this mailing list....

This is what I have (inelegantly) done.

# New version of Agda comes.
# I ignore until I need something from it.
# Often this works for a long time.
# When I needed it:

$ agda --version
$ cp -a .cabal cabal-Agda-<corresponding version>
$ <install stable or development version>

# As a precaution for the future (so the above won't be needed):
$ cp -a .cabal cabal-Agda<corresponding version>

# Ooops. I need the stable version of Agda.
# Assuming I have a safe copy of .cabal as above:

$ mv cabal-Agda-<version> .cabal

This works. It is my manual sandbox.

The caveat is that if you go to an old version as above, and you are 
also using cabal for other purposes (such as teaching Haskell in my 
case), you may need to reinstall the things for other purposes.

In any case, it may be that the above warning is telling me that cabal 
will break these other things, and so my manual sandbox is the only 
option? Who knows, in the absence of documentation or self-evident 
program behaviours.

Martin