Closures in OpenSCAD

OpenSCAD doesn’t have built-in support for closures or first-class functions. However, we can simulate the concept using modules and global variables. Here’s an approximation of the closure behavior:

// Global variable to simulate closure state
i = 0;

// This module simulates the intSeq function
module intSeq() {
    // Increment the global variable
    i = i + 1;
    // Return the new value (by echo, as OpenSCAD doesn't have return values)
    echo(i);
}

// Main execution
function main() = let(
    dummy1 = intSeq(),
    dummy2 = intSeq(),
    dummy3 = intSeq(),
    // Reset i to simulate a new closure
    dummy4 = i = 0,
    dummy5 = intSeq()
) 0;

main();

In OpenSCAD, we don’t have the concept of closures or anonymous functions. Instead, we use a global variable i to simulate the state that would be captured by a closure. The intSeq module increments this variable and echoes its value, simulating the behavior of the closure in the original example.

To use this “closure”:

1. We call intSeq() multiple times, which will increment and echo the value of i.
2. To simulate creating a new closure, we reset i to 0.
3. We then call intSeq() again to show that it starts from 1.

When you run this script, you should see output similar to this in the console:

ECHO: 1
ECHO: 2
ECHO: 3
ECHO: 1

Note that this is not a true closure, as the state is global and can be affected by other parts of the program. In OpenSCAD, we’re limited by the language’s features, which are primarily designed for 3D modeling rather than general-purpose programming.

This example demonstrates how we can approximate some programming concepts in OpenSCAD, even when the language doesn’t directly support them. It’s important to remember that OpenSCAD’s primary purpose is for creating 3D models, so many traditional programming features are not available or work differently.