Real time scripting language + MS DLR?

For starters I should let you guys know what I'm trying to do. The project I'm working on has a requirement that requires a custom scripting system to be built. This will be used by non-programmers who are using the application and should be as close to natural language as possible. An example would be if the user needs to run a custom simulation and plot the output, the code they would write would need to look like

variable input1 is 10; variable input2 is 20;

variable value1 is AVERAGE(input1, input2);

variable condition1 is true; if condition1 then PLOT(value1);

Might not make a lot of sense, but its just an example. AVERAGE and PLOT are functions we'd like to define, they shouldn't be allowed to change them or really even see how they work. Is something like this possible with DLR? If not what other options would we have(start with ANTRL to define the grammar and then move on?)? In the future this may need to run using XBAP and WPF too, so this is also something we need to consider, but haven't seen much if anything on dlr & xbap. Thanks, and hopefully this all makes sense.

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Lua is not an option as it is to different from what they are already accustomed to.

Ralf, its going to reactive, and to be honest the timeframe for when the results should get back to the user may be 1/100 of a second all the way up to 2 weeks or a month(very complex mathematical functions).

Basically they already have a system they purchased that does some of what they need, and included a custom scripting language that does what I mentioned above and they don't want to have to learn a new one, they basically just want us to copy it and add functionality. I think I'll just start with ANTRL and go from there.

From stackoverflow

• Firstly I think that defining your own language is not the way to go.

  • Primarily because the biggest productivity gains you can get for programmers or non-programmers are the development tools. You (and 99.9% of the rest of us) are not going to write tools as good as what is out their.
  • Language design is hard.
  • Language support and documentation, also hard

  I would recommend looking for a pre-built solution. If you could find a language that can lock down some functionality, that would be a good starting point. MatLab would be the first that comes to my mind.

  Lastly, ditch the natural language part, BASIC, COBOL and YA-TDWTF-Lang all tried and failed at it.

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  Full disclosure: I work for a company that is developing a generalized domain specific language "system". It's targeted at data-in/text-out applications so it's not apropos and it's not yet to beta. The result is I'm somewhat knowledgeable and biased.

• What kind of real-time requirement are you trying to fulfill? Is the simulation a hard real-time simulation (some kind of hardware-in-the-loop simulation ==> deadline is less than 1/1000 second)? Or do you want the scripting-system to be "reactive" to user-input ==> 1/10 should be sufficient.

  I am no expert regarding MS DLR, but as far as I know, it does not support hard real-time systems. You may want to take a look at the real-time specification for Java (RTSJ)

• Lua

  it's small, fast, easy to embed, portable, extensible, and fun!

• Lua is definitly the best choice for soft real-time system (like computer games). See http://shootout.alioth.debian.org/ for detailed benchmarks.

  However, last time I checked, Lua used a mark-and-sweep garbage collector which can lead to deadline-violation and non-deterministic jitter in real-time systems.

  Javier : it's an incremental GC, and you can easily invoke it at each cycle, that makes it do really small steps. as with anything, test first.

• I believe that you could use theoretically use the DLR, but I'm unsure about support in an XBAP (partially trusted?) scenario.

  If you host the DLR you would quickly be able to take advantage of IronRuby or IronPython scripting. You would want to look at these implementations when creating your own language implementation. If you post your question to the IronPython mailing list I'm sure you would get a better reply around the XBAP scenario, and some of the developers there created ToyScript.