Everyone has experienced the feeling of familiarizing oneself with a technology over a period of a few weeks or months and arriving at the "How did I ever live without this?" moment (hereto forth HDIELWT). I have often pondered that question quite seriously, trying to remember hard how I managed before tool X came along. It has happened to me with many a tool, including Emacs, Common Lisp, Delicious, Reddit, and several Google products, such as Gmail, Reader, Calendar, and Voice.

I often need to query an XML document without having to load it into a native XML database. In a perfect world, I would simply load the document into my editor, sprinkle some XQuery into the document, highlight the portions I want to evaluate, then hit a key combination to view a new window with the results. The whole operation should take all of a few seconds for a large class of XML documents and queries.

Thankfully, this is indeed a perfect world. And, I'm an Emacs user.

A few days ago, I wrote a simple Quicksort implementation in Common Lisp. After that, I started to wonder how other lisps and Perl compared for sorting numbers.

I just read an article comparing the performance of Clojure, Java, Ruby, and Scala. As I read the article, I wondered how Common Lisp compares to the languages covered in the article.

Some time ago, I started to develop programs using tiny, super general, higher-order functions and I began to borrow a little from functional programming. I noticed interesting things about these new programs. They called for special language features that I had until then heard of but never really needed. I'm referring to language features like support for first-class functions, closures, and lexical binding. The programs I produced were smaller and easier to debug than programs written in a traditional procedural style.

What is Emacs?

Emacs is not just an editor. It's an editor construction kit that comes with a half-finished editor. And that's one of the features that makes it by far the best text editor in the world. The other feature is that you program it in Lisp. O.K., so Elisp (Emacs's Lisp) is an antiquated dynamically scoped Lisp, but it's still a real Lisp with Lisp macros and all.