I have just subjected my coworkers to some happy shouting and a jaunty little dance over this news.
This has literally cost me man-days of lost productivity over the years I've been working with Erlang, and it just never made sense to me. Sure, compilers are hard, etc etc, but this is a basic thing. I've seen toy languages implemented as a proof-of-concept that will never see the light of day that managed to output line numbers with their errors. It's part of most "Baby's First Compiler" tutorials.
For those of you stuck with R14B or earlier, Thomas Lindgren's smart_exceptions library will add line number information to exception backtraces: https://github.com/thomasl/smart_exceptions
You will have incomplete stacktraces; tail calls will be removed from the stack trace. However, you'll be able to know where in the current call (and file) the error lies, which was a big problem in Erlang as soon as you had somewhat lengthy functions.
Why didn't they add this before? Lack of time to develop it, or no requests from developers wanting it? I find the latter hard to believe, and the former to be a more likely cause.
Because it isn't that useful in Erlang, so the want to have it has not been that big. Most (proper) Erlang programs happen to be a lot of small functions and you know what function caused the error and the error type to boot in addition.
This information is often enough to quickly figure out what is wrong. The trouble arises when you have a large function you did not break up yet because then finding the culprit is much harder.
While I like the change, there is a risk associated with it. Namely that people will be less inclined to break up their code.
Notable: The old (deprecated) 'regexp' module has been removed. So if any of your code relies on 'regexp', make sure you replace it with the newer 're' module and update your regular expressions accordingly.
It's nice to have that gone just to avoid confusion with the whole "why there are two regular expression modules?".
Off topic, but is there a recommended post detailing various online Erlang learning resources? I'm reading an O'Reilly book and playing around in the shell but I feel like I need more 3rd party resources to really grok what I'm reading.
Pragmatic Bookshelf's Programming Erlang book (written by Joe Armstrong, the inventor of Erlang) is a good starting point. If covers the basics of the languages as well as introducing ETS, OTP, and Mnesia.
The System Documentation section of erlang docs has well written getting started guides: http://erlang.org/doc/ -- they were the only reference we had before these silly books started showing up a few years ago.
(implied: i was erlanging before it was cool. you probably hadn't heard of it back then.)
Just remember to learn Erlang in layers. Vague order of learning: base language/runtime, APIs, more runtime, more APIs, concurrency, behaviors, nodes, more APIs, multi-nodes, ports, drivers, nifs, ...
In addition, they did retry the tests later and found no performance drop.
But do carry out tests if you are hitting the performance ceiling. A particular use of a particular construct may be hampered when people rewrite a piece of code. So while the overall performance might improve, your case may not.
