branch: externals/peg
commit 26703e869548d233effabc98a537707a3a8ce8e9
Author: Stefan Monnier <monn...@iro.umontreal.ca>
Commit: Stefan Monnier <monn...@iro.umontreal.ca>
* peg.el: Add named rulesets
(define-peg-ruleset): New macro.
(with-peg-rules): Allow reference to a ruleset.
---
peg.el | 57 +++++++++++++++++++++++++++++++++++++++++++++++++--------
1 file changed, 49 insertions(+), 8 deletions(-)
diff --git a/peg.el b/peg.el
index 0d0cab8ca1..0eedca89f3 100644
--- a/peg.el
+++ b/peg.el
@@ -86,6 +86,26 @@
;; buffer text. Rules can be recursive or mutually referential,
;; though care must be taken not to create infinite loops.
;;
+;;;; Named rulesets:
+;;
+;; You can define a set of rules for later use with:
+;;
+;; (define-peg-ruleset myrules
+;; (sign () (or "+" "-" ""))
+;; (digit () [0-9])
+;; (nat () digit (* digit))
+;; (int () sign digit (* digit))
+;; (float () int "." nat))
+;;
+;; and later refer to it:
+;;
+;; (with-peg-rules
+;; (myrules
+;; (complex float "+i" float))
+;; ... (peg-parse nat "," nat "," complex) ...)
+;;
+;;;; Parsing actions:
+;;
;; PEXs also support parsing actions, i.e. Lisp snippets which are
;; executed when a pex matches. This can be used to construct syntax
;; trees or for similar tasks. The most basic form of action is
@@ -144,7 +164,7 @@
;; pushes values to the stack without consuming any, and the latter
;; pops values from the stack and discards them.
;;
-;; Derived Operators:
+;;;; Derived Operators:
;;
;; The following operators are implemented as combinations of
;; primitive expressions:
@@ -195,7 +215,7 @@
;;
;; See ";;; Examples" in `peg-tests.el' for other examples.
;;
-;; References:
+;;;; References:
;;
;; [Ford] Bryan Ford. Parsing Expression Grammars: a Recognition-Based
;; Syntactic Foundation. In POPL'04: Proceedings of the 31st ACM
@@ -221,6 +241,7 @@
;; - Use OClosures to represent PEG rules when available, and let cl-print
;; display their source code.
;; - New PEX form (with RULES PEX...).
+;; - Named rulesets.
;; Version 1.0:
;; - New official entry points `peg` and `peg-run`.
@@ -359,16 +380,36 @@ sequencing `and' operator of PEG grammars."
,(byte-run--set-speed id nil -1)
(put ',id 'byte-optimizer #'byte-compile-inline-expand))))))))
+(defmacro define-peg-ruleset (name &rest rules)
+ "Define a set of PEG rules for later use, e.g., in `with-peg-rules'."
+ (declare (indent 1))
+ (let ((defs ())
+ (aliases ()))
+ (dolist (rule rules)
+ (let* ((rname (car rule))
+ (full-rname (format "%s %s" name rname)))
+ (push `(define-peg-rule ,full-rname . ,(cdr rule)) defs)
+ (push `(,(peg--rule-id rname) #',(peg--rule-id full-rname)) aliases)))
+ `(cl-flet ,aliases
+ ,@defs
+ (eval-and-compile (put ',name 'peg--rules ',aliases)))))
+
(defmacro with-peg-rules (rules &rest body)
"Make PEG rules RULES available within the scope of BODY.
RULES is a list of rules of the form (NAME . PEXS), where PEXS is a sequence
-of PEG expressions, implicitly combined with `and'."
+of PEG expressions, implicitly combined with `and'.
+RULES can also contain symbols in which case these must name
+rulesets defined previously with `define-peg-ruleset'."
(declare (indent 1) (debug (sexp form))) ;FIXME: `sexp' is not good enough!
- (let ((rules
- ;; First, macroexpand the rules.
- (mapcar (lambda (rule)
- (cons (car rule) (peg-normalize `(and . ,(cdr rule)))))
- rules))
+ (let* ((rulesets nil)
+ (rules
+ ;; First, macroexpand the rules.
+ (delq nil
+ (mapcar (lambda (rule)
+ (if (symbolp rule)
+ (progn (push rule rulesets) nil)
+ (cons (car rule) (peg-normalize `(and . ,(cdr
rule))))))
+ rules)))
(ctx (assq :peg-rules macroexpand-all-environment)))
(macroexpand-all
`(cl-labels
