Code Notelets

I had finished writing a piece of software in Ruby in for Linux and wanted to test it also on PC. Since the software involved reading in some data from files, I wanted to be sure that the pathnames could be handled on PC. In Lisp, this is handled with relative ease where it's possible to specify the subdirectory of interest, and the file(s) within that, and it's up to the Lisp implementation to handle the differences between different operating systems.  I was rather expecting something similar for Ruby (given its influence from Lisp), but to my surprise, the official documentation on the File class had no information that I could find as to how pathnames would be handled differently on different operating systems.  Then I looked at the docs for the Ruby IO class , and found the information there. It says: Ruby will convert pathnames between different operating system conventions if possible. For instance, on a Windows system the filename "/gumby/ruby/test.rb" will ...

Learning to use unwind-protect in Lisp typically crops up very early on when you're first learning the language. In fact, anything to do with I/O is going to be something you'll need to know early on. Yet unfortunately, I find that unwind-protect is not explained sufficiently well for a beginner to understand not just how to use it correctly, but why and when . Grappling with this myself, I found that hands-down the best explanation came from this YouTube video from Baggers: Luckily, in the case of file handlers, LISP already assumes you'll want to open a file with unwind-protect, so it provides the with-open-file macro for this exact purpose. It closes the file handler for you with a built-in unwind-protect. This is an advantage over manually opening and closing your file handlers, because if your program opens the file but never gets to the part with the close command (for example due to a run-time error in between those stages), the built-in unwind-protect make...