Line Filters in OpenSCAD

Here’s the translation of the Go line filter program to OpenSCAD, along with explanations:

A line filter is a common type of program that reads input, processes it, and then prints some derived result. In OpenSCAD, we can simulate this behavior using string operations and file I/O.

Here’s an example line filter in OpenSCAD that writes a capitalized version of all input text:

// Function to capitalize a string
function capitalize(str) = 
    len(str) > 0 ? 
        chr(ord(str[0]) >= 97 && ord(str[0]) <= 122 ? ord(str[0]) - 32 : ord(str[0])) 
        * capitalize(substr(str, 1)) 
    : "";

// Read input file
input_file = "input.txt";
lines = split(file(input_file, false), "\n");

// Process each line and write to output file
output_file = "output.txt";
for (line = lines) {
    capitalized_line = capitalize(line);
    echo(capitalized_line);
    write(output_file, str(capitalized_line, "\n"));
}

In this OpenSCAD script:

1. We define a capitalize function that converts a string to uppercase. OpenSCAD doesn’t have a built-in uppercase function, so we implement it manually.

2. We read the input from a file named “input.txt” using the file() function and split it into lines.

3. We process each line by capitalizing it using our capitalize function.

4. We echo the capitalized line to the console and write it to an output file named “output.txt”.

To use this line filter:

1. Create an input file named “input.txt” with some lowercase text:

hello
filter

2. Run the OpenSCAD script. It will create an “output.txt” file and also echo the capitalized lines to the console:

HELLO
FILTER

3. Check the contents of “output.txt” to see the capitalized lines.

Note that OpenSCAD is primarily a 3D modeling language and doesn’t have built-in support for command-line input/output or file manipulation like Go does. This implementation simulates the behavior of a line filter using file I/O, which is typically used for importing 3D model data in OpenSCAD.