Joan Iglesias wrote:

> Hello
> 
> I'm studing Ruby and in a short Ruby in Rails for the web development.
> I've observed that each verion of Ruby can introduce modifications in
> the sintax and behaviour of Ruby. In the other hand I suppose the
> comunity develop libraries in the stable release of the moment. The
> question is:
> 
> What about backward compatibilty? If I write a Ruby program using 1.8.5,
> in the future I'll be able to run in using the Ruby 2.0? What about the
> libraries developed under 1.8 Ruby?

Language developers have every incentive to maintain backward compatibility.
It is rare to see a new language version that breaks old applications. This
isn't a guarantee, it's a statement of a common-sense principle.

Sometimes a language change takes place to avoid what would otherwise have
been a security hole or a syntactical inconsistency, but these sorts of
changes tend to be rare, small and easily repaired in source.

It would be fatal for a language maintainer to create a new language version
that invalidates a lot of old programs.

-- 
Paul Lutus
http://www.arachnoid.com