Anyone interested in "package versioning"?

[Hans Hübner]

2016-05-22 13:33 GMT+02:00 Anton Vodonosov <avodonosov at yandex.ru>:

> 19.05.2016, 11:00, "Hans Hübner" <hans.huebner at gmail.com>:
> > The real issue though is data types defined by versioned libraries.
> Suppose that an instance of a data type defined in library A version 1 is
> passed, through higher levels of the software, to version 2 of that same
> library.  How would one ever expect that to work?
>
> Can that happen without us on the higher level knowingly passing object
> created by one API, to another, incompatible API, which doesn't accept such
> objects?
>
> I was thinking about that too, but now it appears to me that if
> incompatible changes in API are marked as such (e.g. by giving the API new
> name), we always know that the second API is incompatible and can not
> accept this object.
>
> Do you have examples? It would be interesting to explore this problem
> further.
>

Let's assume that we're using, say, an XML library that can parse dates
into instances of a date library, and a database library that accepts
instances of date objects of said library for insertion into a database.
If the XML library and the database library depended on different versions
of the date library and it'd be allowed to have two versions of the date
library in one running lisp image, we'd end up passing date instances
created by the XML library to the database library.

-Hans
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