Apparently this was a research project. Anyone have links to papers, conclusions, results? Should be interesting…
Some of the interesting ones:
- An overview of how memoization works and the MVCC model behind the scenes: http://skiplang.com/blog/2017/01/04/how-memoization-works.ht...
- How pattern matching is implemented and the tricks to make goto work in JavaScript: http://skiplang.com/blog/2017/11/15/simulating-goto-in-javas...
- The work done on making error messages much more helpful by understanding common idioms from other programming languages: http://skiplang.com/blog/2017/11/20/fixing-the-syntax-barrie...
- The macro syntax that elegantly solves a lot of use cases where dynamism is commonly used http://skiplang.com/blog/2018/07/24/macros.html
https://sw1nn.com/blog/2012/04/11/clojure-stm-what-why-how/
The gist of it is that instead of tracking multiple separate locations in memory for values, the software transactional memory (STM) references data by value. So if you assign the value {a: 42, b: 24} to two variables x and y, that value is only stored in memory in one place that the variables both point to. Then if one of the variables changes something, for example y.b = 25, this big tree structure works like copy-on-write and makes copies of branches when mutations occur. So internally, a: 42 is one reference and b: (24 or 25) is another reference. So rather than using 4 cells of memory, we've only used 3.
This frees the developer from having to micromanage memory resources and makes a lot of other things like concurrency "just work" without locks. Do I have this correct?
The practical application is having a webserver that runs a bunch of requests in parallel but that can all share the same memoization cache. We don't want to lock the full memoization cache and therefore block all the other requests when one thread writes a new value.
As far as results, we saw some great numbers for the effectiveness of the recomputation. The language is self hosted. And the type checker is currently incremental. On my machine the initial type checking of the compiler itself is in the ballpark of ~40s. Changing a file and getting new type errors returns in <0.5s