Notebooks

Just like everybody else who starts to look at monads, I found it was like coming to the face of a sheer cliff.  Let me qualify that: just like every other programmer who is not a mathematician (and that’s most of us).  I am looking at monads in the context of clojure, so code snippets will generally be written in clojure-like syntax.

I have found these resources the most helpful:

• Adam Smyczek’s Introduction to Monads on YouTube
• Santosh Rajan’s blog Functional JavaScript
• Jim Duey’s discussion of monads on his blog about Clojure

Continue reading “Monad; that’s a wrap!”

How do you search for strings within a zip archive?

I’m tinkering with EPUB3 files, and I wanted to be able to find certain strings within .epub files, so I had a look around, and I immediately found zgrep and family. The trouble was that zgrep assumes a single zipped file, not an archive.

So, without further ado, I wrote the following script, which I called, naturally, zipgrep. It uses grep and unzip, which it assumes to be available on the PATH.  Not wanting to have to pick through the argument list, I decided to mark the end of arguments to grep with the traditional ‘—‘, after which I could stack up as many zip file names as I liked.

Continue reading “zargrep: grep files in a zip archive”

This method uses launchctl to manage environment variables for programs invoked directly from Finder.  See the launchctl man page, especially the section LEGACY SUBCOMMANDS.  It’s not entirely accurate, but that’s not unusual.  The critical subcommands are getenv, setenv, and unsetenv. The man page indicates that the export subcommand is available; it is not.

Continue reading “Setting environment variables in MacOS Big Sur”

I was looking for a way to process a list of items in an ant build file, similar to what you would do in Java with a construct like:

for ( Element element : elements ) {
    // do stuff with element
}

The approach of XSLT, using recursive calls with local variables, looked promising. In the ant-user mailing list, I found a posting on the topic Implementing a loop in ANT with something like what I was looking for. Ben Stringer’s example gave me the critical information—that I could make indirecly recursive calls to antcall. He also used an external file, updated with the buildnumber task, to maintain state through the recursive calls. Bingo!

Continue reading “Ant: process elements in a list”

One of the frustrations of using ant was the difficulty of deriving one property value performing some sort of editing operation on an existing property value. The mapper task does a lot of grunt work for file names, but not for property values as such.

A common requirement is to map a Java package name to a corresponding directory structure. I have a property containing the package name, and I want to create another property with the directories. Here’s one way to do that. Continue reading “Ant: edit property values”