[parenscript-devel] Re:Js macro names can't be used as variable names

Red Daly reddaly at gmail.com
Sun Jun 17 19:14:32 UTC 2007

I am away from a lispy computer, but here are the problem areas in js.lisp:

(defun js-expand-form (expr) "Expand a javascript form." (cond ((atom expr)
(multiple-value-bind (js-macro macro-env) (lookup-macro expr) (if js-macro
(js-expand-form (let ((*js-macro-env* macro-env)) (funcall js-macro)))
;;; macros (define-js-compiler-macro macrolet (macros &rest body) (let*
((macro-env (make-hash-table :test 'equal)) (*js-macro-env* (cons macro-env
*js-macro-env*))) (dolist (macro macros) (destructuring-bind (name arglist
&rest body) macro (setf (gethash (symbol-name name) macro-env) (compile nil
`(lambda ,arglist , at body))))) (js-compile `(progn , at body))))

(defjsmacro symbol-macrolet (macros &rest body) `(macrolet ,(mapcar
#'(lambda (macro) `(,(first macro) () ,@(rest macro))) macros) , at body))

The problem is that symbol-macrolets use the same machinery as regular
macrolets. A solution is to maintain parallel symbol and regular macro

;; new variables
(eval-when (:compile-toplevel :load-toplevel :execute)
(defvar *js-symbol-macro-toplevel* (make-hash-table :test 'equal) "Toplevel
of symbol macro expansion, holds all the toplevel javascript macros.")
(defvar *js-symbol-macro-env* (list js-symbol-macro-toplevel*) "Current
symbol macro environment."))

;; amend (lookup-macro ..) to take a :type argument.
(defun lookup-macro (name &keyword (type :lambda))
"Lookup the macro NAME in the current macro expansion environment. Returns
the macro and the parent macro environment of this macro." (unless (symbolp
name) (return-from lookup-macro nil)) (do ((env (case type
(:lambda *js-macro-env*)
(:symbol *js-symbol-macro-env*)
(t (error "Invalid macro type ~A" type)))
(cdr env))) ((null env) nil) (let ((val (gethash (symbol-name name) (car
env)))) (when val (return-from lookup-macro (values val (or (cdr env) (list
(case type
(:lambda *js-macro-toplevel*)
(:symbol *js-symbol-macro-toplevel*)
(t (error "Invalid macro type ~A" type))))))))))

;; get rid of (defjsmacro symbol-macrolet ...) and replace it with
;; a compiler macro:
(define-js-compiler-macro symbol-macrolet (macros &rest body) (let*
((macro-env (make-hash-table :test 'equal)) (*js-symbol-macro-env* (cons
macro-env *js-symbol-macro-env*))) (dolist (macro macros) (setf (gethash
(symbol-name (first macro)) macro-env) (compile nil `(lambda () ,@(rest
macro))))) (js-compile `(progn , at body))))

;; change expand-form
(defun js-expand-form (expr) "Expand a javascript form." (cond ((atom expr)
(multiple-value-bind (js-macro macro-env) (lookup-macro expr :type :symbol)
(if js-macro (js-expand-form (let ((*js-symbol-macro-env* macro-env))
(funcall js-macro))) expr))) ((js-compiler-macro-form-p expr) expr) ((equal
(first expr) 'quote) expr) (t (let ((js-macro (lookup-macro (car expr))))
(if js-macro (js-expand-form (apply js-macro (cdr expr))) expr)))))

This should at least give an idea of the relevant areas of code.

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