People don't run the same code on different platforms, except when it's too hard not to

TL;DR - Google uses GWT and j2objc to implement Operational Transforms on all platforms - so I shouldn't expect to be able to implement them for myself.

Most of us write code that only runs on one part of our whole product. I write python code for the server and javascript for the client. Facebook famously gave up on HTML5 for the iPhone. Cross-platform UI toolkits like wxWidgets, Qt or GTK are by definition doomed to the lowest common denominator (you could, in theory, reimplement the best features of each, but that's not been happening). Several attempts have been made to run Microsoft technologies on Unix (IE for UNIX, Wine and Mono), which have had mainly marginal importance - though the jury is out on Mono.

I and some friends spent pretty much all of last year trying to fit a data-heavy app into mobile HTML5. That was one of the many mistakes we made.

As a young sysadmin I settled on perl, since it ran on DOS and Linux (and later Windows). That went pretty well, but you wouldn't really build client applications with it.

But there is a big payout waiting for those who manage radical reuse.

The biggest case is HTML and javascript, especially on the desktop. Mobile HTML works for reading a newspaper, but not for building a rich client. I've recently seen people struggle with HTML and javascript on set-top-boxes, which supposedly run Webkit but in practice tie you to a very proprietary widget environment.

I find that some of the most interesting reuse is when there is a significant technological component that's being reused.

Both iOS's and Android's success builds on reusing the operating system and lower-level libraries (OS-X/FreeBSD and Linux, respectively). Symbian tried to ignore the need to re-use lower-level code, and failed partially due to that.

Oracle's success builds on letting people run its databases and clients on all sorts of OS's.

And now we have Google and Google Docs (Drive). Docs implements the world's best collaborative editing through Operational Transforms (OT). OT are a technological innovation similar to the relational model: a reasonably simple theory, which requires super-human engineering effort to make into a working product. That effort is large enough that you don't want to do it multiple times on multiple platforms. In both Oracle's and Docs's case you also want the results on different platforms to be exactly the same - for OT in real time.

Google is writing the OT code in Java for their servers and Android, and using GWT and j2objc to convert the code to the web and iPhone. And that's atypical even for Google. GWT's not really been a success for Google or others in other areas, especially not for UI.

So Operating Systems, Databases and Operational Transforms are too hard to reimplement. What else?

(This post brought to you by me trying to come up with a reasonable solution to syncing data between mobile clients without wasting all my time on that instead of building actual applications, like Shozu did.)