Recover in Modelica

In Modelica, there isn’t a direct equivalent to Go’s panic and recover mechanism. However, we can demonstrate a similar concept using exceptions and try-catch blocks. Here’s an example that mimics the behavior:

model RecoverExample
  function mayFail
    output Real result;
  algorithm
    assert(false, "a problem");
  end mayFail;

  function main
  protected
    Real result;
  algorithm
    try
      result := mayFail();
      Modelica.Utilities.Streams.print("After mayFail()");
    else
      Modelica.Utilities.Streams.print("Recovered. Error:\n" + getInstanceName());
    end try;
  end main;

equation
  when initial() then
    main();
  end when;
end RecoverExample;

This model demonstrates a concept similar to recovering from a panic. Let’s break it down:

The mayFail function is designed to always fail by using an assert statement with a false condition. This is analogous to the mayPanic function in the original example.

The main function uses a try-catch block to handle the potential failure:

• The try block attempts to call mayFail().
• If mayFail() fails (which it always will in this case), the else branch is executed, which prints a recovery message.

The when initial() equation ensures that main() is called when the simulation starts.

To run this model:

$ omc RecoverExample.mo
$ ./RecoverExample
Recovered. Error:
RecoverExample

In this Modelica example, we use the built-in exception handling mechanism to catch and recover from errors. While it’s not exactly the same as Go’s panic and recover, it serves a similar purpose of allowing the program to continue execution after encountering an error.

Note that in practice, Modelica is primarily used for modeling physical systems and simulations, so this kind of error handling is less common than in general-purpose programming languages. Typically, Modelica tools would handle simulation errors and provide ways to analyze and debug issues in the model.