On Tue, Mar 27, 2012 at 11:22 PM, Achim Gratz <strom...@nexgo.de> wrote: > It needs yet another tool to fully build org-mode from scratch, which > needs to be installed, bug-free and configured correctly. Right now all > one really needs to have to build org-mode is a working Emacs (even make > is optional).
Ragel is written in C++ and has no dependency. * every major platform has a C++ compiler * ragel input along with generated code can be tracked in the repo * the generated code is portable since it's elisp (doesn't need to be regenerated on different platforms) * the parser is a confined part of org-mode I don't think this is a problem. >>> 3) FSM implementation into code is inherently very simple anyway >> >> Well I've never done it for big language but I did not find it that >> easy. Mistakes are easily made e.g. you end up accepting more thing >> that the language does in order to simplify the code, etc. > > Which is just as easily done by specifying the syntax incorrectly. I think the fix will be shorter and simpler in the syntax because it's easier to reason on an abstract definition when it comes to language. When you're neck-deep in your handwritten implementation trying to figure what you did wrong, it can take a long time. > No, you can (for a suitably restricted set of languages) formally proof > that the implementation and the specification is identical for any > input. How would you do that programmatically? > The assumption that an FSM running in ELisp is faster than a bunch of > regexp has not been actually tested or has it? I haven't tested anything yet. If I remember correctly, the emacs regex API doesn't provide a way to compile patterns and thus have to be compiled at each call. Also the underlying FSM implementation uses NFA which can lead to a exponential complexity in time [1] for certain patterns. 1: http://swtch.com/~rsc/regexp/regexp1.html
