A more ambitious undertaking would be to add support for generating embedded JavaScript. Done right, adding JavaScript support to FOO could yield two big wins. One is that after you define an s-expression syntax that you can map to JavaScript syntax, then you can start writing macros, in Common Lisp, to add new constructs to the language you use to write client-side code, which will then be compiled to JavaScript. The other is that, as part of the FOO s-expression JavaScript to regular JavaScript translation, you could deal with the subtle but annoying differences between JavaScript implementations in different browsers. That is, the JavaScript code that FOO generates could either contain the appropriate conditional code to do one thing in one browser and another in a different browser or could generate different code depending on which browser you wanted to support. Then if you use FOO in dynamically generated pages, it could use information about the User-Agent making the request to generate the right flavor of JavaScript for that browser.

1The analogy between FOO’s special operators, and macros, which I’ll discuss in the next section, and Lisp’s own is fairly sound. In fact, understanding how FOO’s special operators and macros work may give you some insight into why Common Lisp is put together the way it is.

3Note that is just another symbol; there’s nothing intrinsically special about names that start with .