[Swift-devel] faster branch

[Mihael Hategan]

Hi,

Over the past couple of weeks I committed the faster branch. It's
essentially a re-implementation of the karajan language. 

The gist of it is that it is now a semi-compiled language. What I mean
by that is that there is no code generation, so the initial parse tree
is converted into a compiled tree. Variable and function references are
resolved at compile-time. This provides considerable improvements in
performance from two fronts:

1. The interpreter was changed from an event-based system (a system that
made sense many years ago, but has little relevance for swift) to a
lightweight threading implementation based on exceptions.
2. The compiler can make optimizations that weren't possible with a
dynamic language. For example, once the swift and logging settings are
known, code that conditionally executes based on a swift property or
logging statements can be optimized away and have no run-time overhead.

There is also a benefit in memory consumed. Variables are now stored in
arrays rather than hashtables. This should reduce the run-time overhead
of the engine.

There are a few more relevant changes from swift's perspective:
- there is no more karajan xml. Keeping two inter-operable syntaxes was
a pain in the back. 
- sites.xml is now parsed with a DOM parser
- all the coaster code has been moved into provider-coaster. Karajan is
now independent of that (and the other way around).

Most of the tests pass, but that means little. So if you can give it a
shot, please do. If it works sufficiently well, we can merge this into
trunk.

Code is at:
https://cogkit.svn.sourceforge.net/svnroot/cogkit/branches/faster/
https://svn.ci.uchicago.edu/svn/vdl2/branches/faster

Mihael

(PS: Contrary to my initial beliefs, the TUI seems to mostly work, but I
haven't tested in detail).