[Haskell-cafe] handling multiple versions of a data structure

[Dmitry V'yal]

On 17.12.2010 01:09, Jeremy Shaw wrote:
> Hello,
>
> You should use happstack-data for this (you do not need the other
> happstack components to use happstack-data)*. It was created to solve
> this exact problem.
>
> happstack-data builds on type of the 'binary' library and adds versioned
> data types and automatic version migration.

Thanks! Looks like what I need. There is a one problem, though. I don't 
have a time machine. I mean right now I have A primitive format based on 
Show instance and I'd like to maintain the compatibility with it.

Is it possible to force a particular on-disk format for a particular 
version of data type? I guess I should write a Serialize instance 
myself. Are there any pitfalls awaiting me?

Best wishes,
Dmitry