When implementing simulation models of complex systems there is always the need to include some, and often a lot, of code to program the logic that gives the simulation entities the desired behavior. For users of the Siemens Tecnomatix Plant Simulation tool, that primarily means writing code in the SimTalk language. I say primarily because Version 2404 released this year added the capability for Python scripts to be added to models. One of my plans for this blog is to write about simulation modelling in Plant Simulation and, as part of that, I want to share SimTalk code samples. However, I couldn't find any tool available to add syntax highlighting to SimTalk code to make it easily readable when published on the web. As a niche language with a small user base (to my knowledge it used only within the Plant Simulation tool), this maybe isn't surprising.

The static site generator that this blog is built with, Pelican, is packaged with a Python-based library called Pygments to provide syntax highlighting. This library, used by thousands of websites including some big ones like Wikipedia, supports hundreds of programming languages, none of which are SimTalk. Fortunately, it is possible to add support for another language by writing a custom lexer. A lexer is a program that converts code (or, more generally, text) into meaningful lexical tokens like keywords, comments, declarations, and operators. So after a few hours of consulting the Pygments docs, writing regular expressions, debugging, and testing I had syntax highlighting working for SimTalk.

I have packaged it as a plugin so all you need to do is install it with pip (or whichever Python package manager you use) and it will be detected automatically by Pygments and made available alongside all the languages it already supports. You can find the installation instructions and source code in the GitHub repository here.

And finally, here are some examples of SimTalk code highlighted with this Pygments SimTalk plugin:

Example 1

param width:length, height:length, depth:length
/* Method that adds a cuboid to the "deco" graphic group 
with dimensions (height, width, length) and the color of wood. */

var cube := _3D.getGraphic("deco").createCuboid([height, width, depth])
cube.MaterialActive := true
cube.MaterialDiffuseColor :=  makeRGBValue(222, 184, 135)  // Wood color.

Example 2

/* Release the circuit board from the source only
once the buffer has less than 3 items */
waituntil Buffer.NumMU < 3
-- Enter the circuit board into the table.
var row: integer
row := CircuitBoards.getColumnYDim(1) + 1
CircuitBoards["circuitBoard", row] := @
CircuitBoards["location", row] := ?
CircuitBoards["entered", row] := EventController.SimTime
@.move -- Move the board onto successor.

Now we just need Siemens to add a dark mode to the Plant Simulation code editor (related forum post)!