People who've made the switch to dynamic languages seem much, much happier. I was a bit out of sorts from jet lag and travel in general when I entered the Birmingham UK conference and suddenly a wash of good feelings poured over me. "Ahh! Python Programmers!"

In this episode I explain how to break hygiene in Scheme macros by using datum->syntax. I discuss how you can play with the lexical context. Finally, I spend some word on non-hygienic macro systems versus hygienic systems.

If there is a topic which is likely to engender a flame war between Schemers and Lispers, that topic is hygienic macros. It is the time to face it, and to explain what people mean when they allude to the "hygiene problem".

In the last dozen episodes I have defined plenty of macros, but I have not really explained what macros are and how they work. This episode closes the gap: it explains the true meaning of Scheme macros by introducing the concepts of syntax object and of transformer over syntax objects.

I showed up at the organizational meeting for the ANSI/ISO C++ standards committee because Bjarne Stroustrup asked me to. I knew him from my early C++ work and from conferences, and I suspect he considered me a friendly influence.

I've seen the next big JVM language, and it's called Scala.

In this episode I add another item to the macro programmer toolkit (macros taking macros as arguments) and I bring an argument in favor of good old parentheses.

After a short introduction about the relevance of macros as tools to design abstractions, including full programming languages, I show some common patterns of Scheme macrology: recursive macros, accumulators, and the usage of literals to incorporate helpers in macros.

At this year's JavaOne, you can notice the buzz around "cloud computing." Vendors seem to have different takes on just what this term means. Then there are fun new languages for the VM, such as Scala, JavaFX, and Clojure. And old languages seem to be moving to the VM, too: There are JavaOne sessions on running PHP on the JVM, for example.

Observations about the organization of the conference and about the talks discussing the future of Common Lisp.

I regularly receive requests for career advice, and I've tried to capture the answers in this blog, and in a follow-on. For those of you who asked but never got an answer, I apologize. Your questions stimulated me to work on this, and it's taken awhile.

Some thoughts about programming-language communities, inspired by the Lisp conference I attended last week.

A pointer to the slides I prepared for the Second European Lisp Symposium http://www.european-lisp-symposium.org/

In the last episode we saw that PLT Scheme performs much more instantiation and visiting of modules than other implementations. The reason for such behaviour is that PLT Scheme aims to avoid cross-phase side effects. In this episode I explain what cross-phase side effects are and why they are evil.

In episode 19 I noticed that the R6RS module system allows for separate compilation, but I have not mentioned the subtilities associated with it. This episode discusses the topic, the concept of visit time and the intricacies of the "import" semantics.