branch: externals/peg
commit 912e9baf50da2ac83fc987336158af2ae0cbda4c
Author: Stefan Monnier <monn...@iro.umontreal.ca>
Commit: Stefan Monnier <monn...@iro.umontreal.ca>
* peg.el: Add support for arguments and indirect calls
(peg-leaf-types): Add `funcall`.
(peg--macroexpand): Rely on the unknown-function machinery to detect
unknown peg rules.
(peg--translate) <call>: Allow passing parameters to PEG rules.
(peg--translate) <funcall>: New rule.
---
peg.el | 35 ++++++++++++++++++++++++++++-------
1 file changed, 28 insertions(+), 7 deletions(-)
diff --git a/peg.el b/peg.el
index 0eedca89f3..367aef468c 100644
--- a/peg.el
+++ b/peg.el
@@ -69,6 +69,7 @@
;; Boolean-guard (guard EXP)
;; Syntax-Class (syntax-class NAME)
;; Local definitions (with RULES PEX...)
+;; Indirect call (funcall EXP ARGS...)
;; and
;; Empty-string (null) ε
;; Beginning-of-Buffer (bob)
@@ -215,6 +216,23 @@
;;
;; See ";;; Examples" in `peg-tests.el' for other examples.
;;
+;;;; Rule argument and indirect calls:
+;;
+;; Rules can take arguments and those arguments can themselves be PEGs.
+;; For example:
+;;
+;; (define-peg-rule 2-or-more (peg)
+;; (funcall peg)
+;; (funcall peg)
+;; (* (funcall peg)))
+;;
+;; ... (peg-parse
+;; ...
+;; (2-or-more (peg foo))
+;; ...
+;; (2-or-more (peg bar))
+;; ...)
+;;
;;;; References:
;;
;; [Ford] Bryan Ford. Parsing Expression Grammars: a Recognition-Based
@@ -242,6 +260,9 @@
;; display their source code.
;; - New PEX form (with RULES PEX...).
;; - Named rulesets.
+;; - You can pass arguments to rules.
+;; - New `funcall' rule to call rules indirectly (e.g. a peg you received
+;; as argument).
;; Version 1.0:
;; - New official entry points `peg` and `peg-run`.
@@ -478,14 +499,12 @@ rulesets defined previously with `define-peg-ruleset'."
(apply #'peg--macroexpand exp))
(defconst peg-leaf-types '(any call action char range str set
- guard syntax-class =))
+ guard syntax-class = funcall))
(cl-defgeneric peg--macroexpand (head &rest args)
(cond
((memq head peg-leaf-types) (cons head args))
- ((null args) `(call ,head))
- (t
- (error "Invalid parsing expression: %S" (cons head args)))))
+ (t `(call ,head ,@args))))
(cl-defmethod peg--macroexpand ((_ (eql or)) &rest args)
(cond ((null args) '(guard nil))
@@ -767,9 +786,11 @@ rulesets defined previously with `define-peg-ruleset'."
(goto-char (match-end 0))
t))
-(cl-defmethod peg--translate ((_ (eql call)) name)
- ;; (peg--lookup-rule name) ;; Signal error if not found!
- `(,(peg--rule-id name)))
+(cl-defmethod peg--translate ((_ (eql call)) name &rest args)
+ `(,(peg--rule-id name) ,@args))
+
+(cl-defmethod peg--translate ((_ (eql funcall)) exp &rest args)
+ `(funcall ,exp ,@args))
(cl-defmethod peg--translate ((_ (eql action)) form)
`(progn
