[Haskell-cafe] Binary and Serialize classes

[Evan Laforge]

> When I need to comply with a specific binary format, I never rely on
> Binary/Serialize class instances - I always fall back on the primitive
> operations on Words of varying sizes (perhaps defining my own type
> classes for convenience). The 'Builder' type makes this pretty easy.
>
> If I were writing binary data to disk, in my mind that would fall
> under "complying with a specific binary format".

Indeed, and I was starting to do that... well, I would make my own
project specific Serialize class, since the type dispatch is useful.
But copy pasting a UTF8 encoder, or the variable length Integer
encoder, or whatever seemed kinda unpleasant.  Surely we could expose
that stuff in a library, whose explicit goal was that they *would*
remain compatible ways to serialize various basic types, and then just
reuse those functions?  E.g. that is already done for words with the
putWordN{be,le} functions, and is available separately for UTF8.

> I do, however, rely on the SafeCopy class (or the equivalent
> Happstack.Data.Serialize class) to be able to read it's own data back
> from persistent storage - it is a specific design goal of the library

Indeed, I also wound up inventing my own versioning format, which
looks basically the same as safe copy, except much simpler, I just put
a version byte, and then case on that for deserialization.  However, I
only put the version on things I have reason to change, and that
doesn't include built-in data types, like Integer or String.  So it's
all my own data types, which I control the instance declarations for
anyway, so I'm not really worried about those.