Rants from the Ballmer Peak 
Could Dropbox switch to Nim?
More interesting changes have been announced in the language arena just a few days after I wrote my opinion on Facebook announcing the Hack programming language. So rather than a longish useless rant, this is more like an appendix to that article. The interesting things announced were:
- Microsoft announces .NET Native, which essentially compiles C# with their C++ backend.
- Dropbox announces Pyston, a JIT-based Python implementation.
Both of these announces highlight that anything dynamic has trouble in the real world out there. Scaling servers is cool, but not having to throw millions at hardware and still meet your goals is even better. The perspective for both companies is different, though. Microsoft is likely targeting embedded developers, aka, writing C# code for Windows Phone or Xbox and keep 60 frames per second while consuming the minimum possible amount of resources. On the other hand, the Dropbox announcement is particularly interesting:
"After some abandoned experiments with static compilation, we looked around and saw how successfully JIT techniques are being applied in the JavaScript space[...]"
This is really intriguing. Static compilation tends to solve the performance problems, but might introduce other development downsides. Other commenters of the blog post itself mention several alternatives to statically compiling Python, as in "did you try this? why isn't it good?". Many of them have performance limits imposed by the language: you either can't optimize a dynamic language all the way compared to other statically compiled languages, or you have to restrict yourself to a subset of Python or modify it, which depending on how you do you may need to throw away your existing code.
But instead of going the way of Facebook and adding optional static typing they are instead keeping the dynamic nature of the language and instead looking at providing type speculation. Based on the blog post description of type speculation, you can likely understand more by watching the Strange Loop talk Why Ruby Isn't Slow by Alex Gaynor. Really nice talk, it mentions the horrible RPython implementation (Alex's words, not mine) which allows defining these probabilistic hints for the optimizer, like: "well, this property is now a string, and it is 99% likely going to be a string all the time, so maybe you should actually ignore type checks and indirections and stuff and directly access it like a string". If you are interested in dynamic languages evolution and optimization, you can also watch Fast and Dynamic by Maxime Chevalier-Boisvert.
Of course I would propose using the Nim programming language to any Python programmer looking for a more performant, saner language. But Dropbox didn't start yesterday to write code, and surely they have tons of code. They must have considered that keeping with Python and implementing a faster interpreter is more cost effective than switching to a different language. Don't think just in terms of rewriting code but also in retraining their workforce or hiring people with practical previous experience.
So unfortunately Nim is not a viable option for companies like Dropbox. Not Nim, not any other language. Just like I concluded in my previous blog post, the Dropbox team has succeeded with Python, and now their success is killing them. Developing a faster interpreter for Python is not a trivial matter, or it would have already been done, so one can only hope that the Dropbox developers really know what they are doing starting Pyston. Or maybe they have tons of money to burn, which offsets nearly any worries a normal programmer has about decision failures.
$ nim c -r bank_savings.nim Traceback (most recent call last) bank_savings.nim(135) bank_savings bank_savings.nim(107) end_of_month bank_savings.nim(79) pay_rent SIGSEGV: Illegal storage access. (Attempt to read from nil?) Error: execution of an external program failed