WebPPL provides error messages that try to be informative. In addition there is debugging software you can use for WebPPL programs.

To debug WebPPL programs running in Chrome, enable pause on JavaScript exceptions in the Chrome debugger.

To debug WebPPL programs running in nodejs, use node debugger as follows:

  1. Add debugger; statements to my-program.wppl to indicate breakpoints.

  2. Run your compiled program in debug mode:

    node debug path/to/webppl my-program.wppl

    Note that you will need the full path to the webppl executable. This might be in the lib folder of your node directory if you installed with npm. On many systems you can avoid entering the path manually by using the following command:

    node debug `which webppl` my-program.wppl
  3. To navigate to your breakpoint within the debugger interface, type cont or c. At any break point, you can type repl to interact with the variables. Here’s some documentation for this debugger.