What is the motivation for using lists as the intermediate form rather than CLOS objects? I suppose that s-expressions makes it easy to use tree-walking functions out of the box, but there seem to be disadvantages when it comes to separating syntax from semantics, e.g. addressing the 'else' form of an if via (third if-statement) vs. (if-statement-else if-statement). I have not seen the intermediary form and I am sure you have good reasons, but it is not the direction I would have gone. Could you explain the choice perhaps with some motivating examples, to enlighten us all?
Here's an example of what the current intermediate form looks like:
(compile-statement '(defun blep (ss x y) (when foo? (let ((pair (bar))) (unless (null pair) (destructuring-bind (a b) pair (unless (or (null a) (null b)) (let ((val (baz a b))) (unless (null val) (when (blah val) (unless (blee) t)))))))))))
=>
(JS:DEFUN BLEP (SS X Y) (JS:BLOCK (JS:IF FOO? (JS:BLOCK (JS:VAR PAIR (JS:FUNCALL BAR)) (JS:IF (JS:!== PAIR NIL) (JS:BLOCK (JS:VAR A (JS:AREF PAIR 0)) (JS:VAR B (JS:AREF PAIR 1)) (JS:IF (JS:! (JS:|||| (JS:=== A NIL) (JS:=== B NIL))) (JS:BLOCK (JS:VAR VAL (JS:FUNCALL BAZ A B)) (JS:IF (JS:!== VAL NIL) (JS:BLOCK (JS:IF (JS:FUNCALL BLAH VAL) (JS:BLOCK (JS:IF (JS:! (JS:FUNCALL BLEE)) (JS:BLOCK (JS:RETURN T)))))))))))))))
As you can see, all you need is to define some functions and macros, and the resulting code is ready to be EVALed or compiled.
Go, Vladimir, go! That's an ambitious project but I would love to see it happen! Please not that there is a project with a viable javascript parser and printer already. See http://github.com/gonzojive/js-parser I adapted the code from JWACS (Javascript With Advanced Continuations Support) into a new project for parsing javascript. The original JWACS included a pretty printer and an obfuscating printer that would obfuscate non-toplevel variables. It also had a Javascript-like grammar with a few extra syntax additions. The syntax tree represents javascript with structures rather than lists for everything, but you should be able to avoid writing the parser yourself, at the very least.
Thanks for the pointer. I didn't know you based your parser on JWACS'. I took a look at JWACS when starting, but decided to base mine on Marijn Haverbeke's parse-js (http://marijn.haverbeke.nl/parse-js/); it seemed easier to modify.
Vladimir
One user-visible change I made in the latest patches is to encourage use of CL equality predicates ('==' and '===' are still there but marked as deprecated).
Vladimir
Red
2010/4/19 John Pallister john@synchromesh.com:
+1, as they say...
++Thanks,
John :^P
On Mon, Apr 19, 2010 at 12:42 AM, Daniel Gackle danielgackle@gmail.com wrote:
For those of us who are curious, could you talk a bit about the work you did on the compiler? Thanks Vladimir, Daniel
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