Defer in Scilab

In Scilab, there isn’t a direct equivalent to the defer keyword. However, we can achieve similar functionality using try-catch-finally blocks. Here’s how we can implement a similar concept:

function f = createFile(p)
    disp("creating")
    [f, err] = mopen(p, 'w')
    if err ~= 0 then
        error("Cannot create file")
    end
endfunction

function writeFile(f)
    disp("writing")
    mfprintf(f, "data\n")
endfunction

function closeFile(f)
    disp("closing")
    mclose(f)
endfunction

function main()
    try
        f = createFile("/tmp/defer.txt")
        writeFile(f)
    catch
        disp("An error occurred")
    finally
        closeFile(f)
    end
endfunction

main()

In this example, we’re simulating the behavior of defer using a try-finally block. The finally block ensures that the file is closed, regardless of whether an error occurred or not.

Let’s break down the code:

1. createFile function opens a file for writing and returns the file handle.
2. writeFile function writes some data to the file.
3. closeFile function closes the file.
4. In the main function:
   • We open the file using createFile.
   • We write to the file using writeFile.
   • The finally block ensures that closeFile is called, similar to how defer would work.

It’s important to note that in Scilab, error handling is typically done using try-catch blocks. The finally block is always executed, whether an exception is thrown or not, making it a good place for cleanup operations like closing files.

Running the program should produce output similar to this:

creating
writing
closing

This approach ensures that the file is closed after being written, mimicking the behavior of the original example.