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

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