Exit in OpenSCAD

Here’s an idiomatic OpenSCAD example demonstrating the concept of exiting a program:

// Function to simulate exiting the program
module exit(status) {
    // In OpenSCAD, we can't actually exit the program,
    // so we'll simulate it by echoing a message
    echo(str("Exiting with status: ", status));
    
    // We can use the assert() function to stop execution
    // This will halt the script and display an error message
    assert(false, str("Program exited with status ", status));
}

// Main part of the script
module main() {
    // This echo statement will be executed
    echo("Starting the program");
    
    // This would normally not be executed in languages with true exit functionality
    echo("This message will not be seen");
    
    // Simulate exiting the program with status 3
    exit(3);
}

// Call the main module to run the script
main();

In OpenSCAD, we don’t have a direct equivalent to the os.Exit() function found in some other programming languages. However, we can simulate the concept of exiting a program using OpenSCAD’s built-in functions and modules.

Here’s how this example works:

1. We define an exit() module that simulates exiting the program. It takes a status code as an argument.

2. Inside the exit() module, we use echo() to print a message about exiting the program.

3. We then use the assert() function with a false condition to halt the script’s execution. This is the closest we can get to “exiting” in OpenSCAD.

4. The main() module represents the main part of our script. It echoes a start message, then calls the exit() module with a status of 3.

5. We call main() at the end to run our script.

When you run this script in OpenSCAD, you’ll see output similar to this in the console:

ECHO: "Starting the program"
ECHO: "Exiting with status: 3"
ERROR: Assertion 'false' failed in file <stdin>, line 9

Note that in OpenSCAD, we can’t truly exit the program or prevent subsequent code from running. The assert() function will halt the script, but it does so by throwing an error, which isn’t ideal for production use.

To run this script:

1. Save it as a .scad file (e.g., exit_example.scad).
2. Open it in the OpenSCAD application.
3. Click “Compile and Render” or press F6 to run the script.

This example demonstrates how to simulate program exit behavior in OpenSCAD, even though the language doesn’t have built-in functionality for this concept.