pegutils.lisp

   1 ;;; -*- Mode: Lisp; Syntax: ANSI-Common-Lisp; Base: 10; -*-
   2 ;;;
   3 ;;; pegutils.lisp --- Utility functions for implementing PEG parsers
   4
   5 ;; Copyright (C) 2008 Utz-Uwe Haus <lisp@uuhaus.de>
   6 ;; $Id$
   7 ;;
   8 ;; This code is free software; you can redistribute it and/or modify
   9 ;; it under the terms of the version 2.1 of the GNU Lesser General
  10 ;; Public License as published by the Free Software Foundation, as
  11 ;; clarified by the lisp prequel found in LICENSE.
  12 ;;
  13 ;; This code is distributed in the hope that it will be useful, but
  14 ;; without any warranty; without even the implied warranty of
  15 ;; merchantability or fitness for a particular purpose. See the GNU
  16 ;; Lesser General Public License for more details.
  17 ;;
  18 ;; Version 2.1 of the GNU Lesser General Public License is in the file
  19 ;; LICENSE that was distributed with this file. If it is not
  20 ;; present, you can access it from
  21 ;; http://www.gnu.org/copyleft/lgpl.txt (until superseded by a
  22 ;; newer version) or write to the Free Software Foundation, Inc., 59
  23 ;; Temple Place, Suite 330, Boston, MA 02111-1307 USA
  24 ;;
  25 ;; Commentary:
  26
  27 ;; Some code here is inspired by the metapeg library of John Leuner
  28
  29 ;;; Code:
  30
  31
  32 (eval-when (:load-toplevel :compile-toplevel :execute)
  33   (declaim (optimize (speed 0) (safety 3) (debug 3))))
  34
  35 (in-package #:opossum)
  36 \f
  37 (defparameter *trace* nil "If non-nil, do extensive tracing of the parser functions.")
  38 \f
  39
  40 (defclass context ()
  41   (;; these slots are copied when cloning a context for recursion
  42    (input       :accessor input       :initarg :input       :initform nil
  43                 :type 'string
  44                 :documentation "The input string being parsed.")
  45    (dst-package :accessor dst-package :initarg :dst-package :initform nil
  46                 :type 'package
  47                 :documentation "The package into which symbols generated during the parse are interned.")
  48    ;; these slots are shared by all cloned copies of a context -- use only STORE-ACTION to guarantee consistency
  49    (actions     :accessor actions     :initarg :actions     :initform (make-list 1 :initial-element NIL)
  50                 :type 'list
  51                 :documentation "The list of actions accumulated during the parse.")
  52    (action-counter :accessor action-counter :initarg :action-counter :initform '(0)
  53                    :type '(cons (integer 0) null)
  54                    :documentation "The counter of actions.")
  55    ;; these slots are what make a context unique
  56    (parent      :accessor parent      :initarg :parent      :initform nil)
  57    (rule        :accessor rule        :initarg :rule        :initform nil)
  58    (children    :accessor children    :initform nil)
  59    (value       :accessor value       :initarg :value       :initform nil)
  60    (start-index :accessor start-index :initarg :start-index :initform nil)
  61    (end-index   :accessor end-index   :initarg :end-index   :initform nil)
  62    (depth       :accessor depth       :initarg :depth       :initform 0
  63                 :documentation "How deep in the tree is this context?"))
  64   (:documentation "The parser context."))
  65
  66 (defmethod print-object ((obj context) stream)
  67   (print-unreadable-object (obj stream :type T :identity NIL)
  68     (format stream "rule ~A (~S) value ~S (~D:~D)"
  69             (rule obj) (children obj) (value obj) (start-index obj) (end-index obj))))
  70
  71 (defmethod store-action ((ctx context) action)
  72   (let ((a (actions ctx)))
  73     (rplacd a (cons (car a) (cdr a)))
  74     (rplaca a action)))
  75
  76 (defvar *context* nil "The current parser context.")
  77
  78 (defun clone-ctx (ctx rule)
  79   "Create clone context of CTX for rule RULE."
  80   (make-instance 'context
  81                  :input (input ctx)
  82                  :dst-package (dst-package ctx)
  83                  :actions (actions ctx)
  84                  :action-counter (action-counter ctx)
  85                  :parent ctx
  86                  :rule rule
  87                  :start-index (end-index ctx)
  88                  :depth (1+ (depth ctx))))
  89
  90 (defun ctx-failed-p (ctx)
  91   (unless ctx
  92     (break "Botched context"))
  93   (null (end-index ctx)))
  94
  95 (defun succeed (ctx value start-index end-index)
  96   "Mark CTX as successful: set VALUE and matched region."
  97   (setf (value ctx) value)
  98   (setf (start-index ctx) start-index)
  99   (setf (end-index ctx) end-index)
 100   ;; (when *trace*
 101   ;;     (format *trace-output* "Matched: ~A (~D:~D)~%"
 102   ;;        (rule ctx) (start-index ctx) (end-index ctx)))
 103   ctx)
 104
 105 (defun fail ()
 106   "Return a failure context."
 107   (let ((ctx (make-instance 'context
 108                             :input (input *context*)
 109                             :rule ':fail
 110                             :value (rule *context*)
 111                             :start-index (start-index *context*)
 112                             :end-index (end-index *context*)
 113                             ;; probably some of these copies can be saved
 114                             :dst-package (dst-package *context*)
 115                             :actions (actions *context*)
 116                             :action-counter (action-counter *context*)
 117                             :depth (1+ (depth *context*)))))
 118     ;; (when *trace*
 119     ;;       (format *trace-output* "(failed: ~A ~A ~A)~%"
 120     ;;        (value ctx) (start-index ctx) (end-index ctx)))
 121     ctx))
 122
 123 \f
 124 ;;
 125 (defun make-name (string)
 126   (intern (concatenate 'string "parse-" string)
 127           (dst-package *context*)))
 128
 129 (defun make-action-name (&key ctx)
 130   "Return a symbol suitable to name the next action."
 131   (incf (car (action-counter *context*)))
 132   (let ((aname (if ctx
 133                    (format nil "opossum-action-~D-srcpos-~D-~D"
 134                            (car (action-counter *context*))
 135                            (start-index ctx)
 136                            (end-index ctx))
 137                    (format nil "opossum-action-~D"
 138                            (car (action-counter *context*)))) ))
 139     (intern aname (dst-package *context*))))
 140
 141 (defun char-list-to-string (char-list)
 142   (coerce char-list 'string))
 143
 144 (defmacro build-parser-function (name parser)
 145   `(lambda (offset)
 146     (let ((indent (depth *context*)))
 147       (when *trace* (format *trace-output* "~vTTrying to parse a ~A at pos ~D~%" indent ,name offset))
 148       (let* ((*context* (clone-ctx *context* ,name))
 149              (result (funcall ,parser offset)))
 150         (unless result
 151           (error "Parser function ~A did not return a value" ,parser))
 152         (if (ctx-failed-p result)
 153             (progn
 154               (when *trace* (format *trace-output* "~vT... no ~A at pos ~D~%" indent ,name offset))
 155               (fail))
 156             (progn
 157               (when *trace* (format *trace-output* "~vT... found ~A at ~D:~D~%"
 158                                     indent
 159                                     ,name (start-index result) (end-index result)))
 160               (succeed *context* (value result) (start-index result) (end-index result))))))))
 161
 162
 163 \f
 164 (defun match-string (string)
 165   #'(lambda (offset)
 166       (let ((input (input *context*))
 167             (len (length string)))
 168         (if (and (>= (length input) (+ offset len))
 169                  (string= string input :start2 offset :end2 (+ offset len)))
 170             (succeed (clone-ctx *context* 'opossum-string) string offset (+ offset (length string)))
 171             (fail)))))
 172
 173 (defun match-char (char-list)
 174   #'(lambda (offset)
 175       (let ((input (input *context*)))
 176 ;;      (when *trace*
 177 ;;        (format *trace-output* "match-char: looking for one of `~{~A~}'~%" char-list))
 178         (if (and (> (length input) offset)
 179                  (member (char input offset)
 180                          char-list :test #'char=))
 181             (succeed (clone-ctx *context* 'opossum-char) (char input offset) offset (+ offset 1))
 182             (fail)))))
 183
 184 (defun match-octal-char-code (i1 i2 i3)
 185   "Compare the character given by i3 + 8*i2 + 64*i1 to the next input character."
 186   (let ((c (+ i3 (* 8 i2) (* 64 i1))))
 187     #'(lambda (offset)
 188         (let ((input (input *context*)))
 189 ;;        (when *trace*
 190 ;;          (format *trace-output* "match-octal-char-code: looking for ~D~%" c))
 191           (if (and (> (length input) offset)
 192                    (= (char-int (char input offset)) c))
 193               (succeed (clone-ctx *context* 'opossum-char) (char input offset) offset (+ offset 1))
 194               (fail))))))
 195
 196 (defun match-char-range (lower-char upper-char)
 197   "Match characters in the range between LOWER-CHAR and UPPER-CHAR (inclusive) as decided by CL:CHAR-CODE."
 198   #'(lambda (offset)
 199       (let ((input (input *context*)))
 200 ;;      (when *trace*
 201 ;;        (format *trace-output* "match-char-range: looking for ~A-~A~%" lower-char upper-char))
 202         (if (and (> (length input) offset)
 203                  (let ((x (char-code (char input offset))))
 204                    (and (>= x (char-code lower-char))
 205                         (<= x (char-code upper-char)))))
 206             (succeed (clone-ctx *context* 'opossum-char-range) (char input offset) offset (+ offset 1))
 207             (fail)))))
 208
 209 (defun match-any-char (&optional ignored)
 210   (declare (ignore ignored))
 211   #'(lambda (offset)
 212       "Match any character at OFFSET, fail only on EOF."
 213       (let ((input (input *context*)))
 214 ;;      (when *trace*
 215 ;;        (format *trace-output* "match-any-char~%"))
 216         (if (< (1+ offset) (length input))
 217             (succeed (clone-ctx *context* 'opossum-anychar) (char input offset) offset (+ offset 1))
 218             (fail)))))
 219
 220 (defun match-char-class (char-class)
 221   "Regexp matching of next input character against [CHAR-CLASS] using cl-ppcre:scan."
 222   (declare (type string char-class))
 223   ;; FIXME: could use a pre-computed scanner
 224   (let ((cc (format nil "[~A]" char-class)))
 225     #'(lambda (offset)
 226         "Match next character at OFFSET against the characters in CHAR-CLASS."
 227         (let ((input (input *context*)))
 228 ;;        (when *trace*
 229 ;;          (format *trace-output* "match-char-class on ~A~%"))
 230           (if (and (< (1+ offset) (length input))
 231                    (let ((c (char input offset)))
 232                      (cl-ppcre:scan cc (make-string 1 :initial-element c))))
 233               (succeed (clone-ctx *context* 'opossum-charclass)
 234                        (char input offset) offset (+ offset 1))
 235               (fail))))))
 236
 237 (defun fix-escape-sequences (char-list)
 238   "Iterate over the list CHAR-LIST, glueing adjacent #\\ #\n and #\\ #\t chars into
 239 #\Newline and #\Tab."
 240   (cond
 241     ((null char-list) char-list)
 242     ((null (cdr char-list)) char-list)
 243     (T
 244      (loop :with drop := nil
 245            :for (c1 c2) :on char-list
 246            :if drop
 247            :do (setf drop nil)
 248            :else
 249            :collect (if (char= c1 #\\)
 250                         (case c2
 251                           ((#\n) (setf drop T) #\Newline)
 252                           ((#\t) (setf drop T) #\Tab)
 253                           ((#\r) (setf drop T) #\Linefeed)
 254                           (otherwise c1))
 255                         c1)
 256            :end))))
 257 \f
 258 ;;
 259 ;; parsing combinator functions cribbed from libmetapeg
 260 ;;
 261 (defun either (&rest parsers)
 262   "Produce a function that tries each of the functions in PARSERS sequentially until one succeeds and
 263 returns the result of that function, or a failure context if none succeeded."
 264   #'(lambda (offset)
 265       (let ((*context* (clone-ctx *context* 'opossum-either)))
 266         ;; (when *trace*
 267         ;;        (format *trace-output* "either: ~A ~A~%" *context* parsers))
 268         (loop :for p :in parsers
 269               :as result = (funcall p offset)
 270               :when (not (ctx-failed-p result))
 271               :return (succeed *context* (value result) offset (end-index result))
 272               :finally (return (fail))))))
 273
 274
 275 (defun optional (parser)
 276   #'(lambda (offset)
 277       (let ((*context* (clone-ctx *context* 'opossum-optional)))
 278 ;;      (when *trace*
 279 ;;        (format *trace-output* "optional: ~A ~A~%" *context* parser))
 280         (let ((result (funcall parser offset)))
 281           (if (ctx-failed-p result)
 282               (succeed *context* 'optional offset offset)
 283               (succeed *context* (value result) offset (end-index result)))))))
 284
 285 (defun follow (parser)
 286   #'(lambda (offset)
 287       (let ((*context* (clone-ctx *context* 'opossum-follow)))
 288 ;;      (when *trace*
 289 ;;        (format *trace-output* "follow: ~A ~A~%" *context* parser))
 290         (let ((result (funcall parser offset)))
 291           (if (ctx-failed-p result)
 292               (fail)
 293               (succeed *context* (value result)
 294                        ;; don't consume input
 295                        offset offset))))))
 296
 297 (defun many (parser)
 298   #'(lambda (offset)
 299       (let ((*context* (clone-ctx *context* 'opossum-many))
 300             (start-offset offset)
 301             children)
 302 ;;      (when *trace*
 303 ;;        (format *trace-output* "many: ~A ~A~%" *context* parser))
 304         (loop :as result := (funcall parser offset)
 305               :while (not (ctx-failed-p result))
 306               :do (progn (push (value result) children)
 307                          (setf offset (end-index result)))
 308               :finally (return (succeed *context* (nreverse children) start-offset offset))))))
 309
 310
 311 (defun many1 (parser)
 312   #'(lambda (offset)
 313       (let* ((*context* (clone-ctx *context* 'opossum-many1))
 314              (result (funcall parser offset)))
 315 ;;      (when *trace*
 316 ;;        (format *trace-output* "many1: ~A ~A~%" *context* parser))
 317         (if (not (ctx-failed-p result))
 318             (let ((result2 (funcall (many parser) (end-index result))))
 319               (if (end-index result2)
 320                   (succeed *context* (cons (value result) (value result2)) offset (end-index result2))
 321                   (succeed *context* (value result) offset (end-index result))))
 322             (fail)))))
 323
 324
 325 (defun seq (&rest parsers)
 326   #'(lambda (offset)
 327       (assert (> (length parsers) 0))
 328       (let ((*context* (clone-ctx *context* 'opossum-seq))
 329             (start-offset offset)
 330             child-values
 331             child-nodes)
 332 ;;      (when *trace*
 333 ;;        (format *trace-output* "seq: ~A ~A~%" *context* parsers))
 334         ;; run the parsers
 335         (loop :for p :in parsers
 336 ;;            :do (when *trace* (format *trace-output* " (seq ~A) trying ~A~%" *context* p))
 337               :do (cond
 338                     ((consp p)
 339                      (push (succeed (clone-ctx *context* 'action) nil offset offset)  child-nodes)
 340                      (push p child-values)
 341                      (setf (children *context*) (reverse child-nodes)))
 342                     (T
 343                      (let ((result (funcall p offset)))
 344                        (if (end-index result)
 345                            (progn
 346                              (push result child-nodes)
 347                              (push (value result) child-values)
 348                              (setf offset (end-index result))
 349                              (setf (children *context*) (reverse child-nodes)))
 350                            (return (fail))))))
 351               :finally (return (succeed *context* (reverse child-values) start-offset offset))))))
 352
 353 (defun negate (parser)
 354   #'(lambda (offset)
 355       "Return a successful context at OFFSET if PARSER succeeds, without advancing input position."
 356       (let ((*context* (clone-ctx *context* 'opossum-negate)))
 357         (let ((result (funcall parser offset)))
 358           (if (ctx-failed-p result)
 359               (succeed *context* 'negate offset offset)
 360               (fail))))))
 361
 362 \f
 363 ;;
 364 (defun read-stream (stream)
 365   "Read STREAM and return a string of all its contents."
 366   (let ((s ""))
 367     (loop :as line := (read-line stream nil nil)
 368           :while line
 369           :do (setq s (concatenate 'string s line)))
 370     s))
 371
 372 (defun read-file (file)
 373   "Read FILE and return a string of all its contents."
 374   (with-open-file (f file :direction :input)
 375     (let ((len (file-length f)))
 376       (if len
 377           (let ((s (make-string len)))
 378             (read-sequence s f)
 379             s)
 380           (read-stream f)))))
 381 \f
 382 (defun make-default-dst-package (grammarfile)
 383   (make-package (gensym "opossum-parser")
 384                 :documentation (format T "Opossum parser for grammar ~A" grammarfile)))
 385
 386 (defun get-iso-time ()
 387   "Return a string in ISO format for the current time"
 388   (multiple-value-bind (second minute hour date month year day daylight-p zone)
 389       (get-decoded-time)
 390     (declare (ignore day))
 391     (format nil "~4D-~2,'0D-~2,'0D-~2,'0D:~2,'0D:~2,'0D (UCT~@D)"
 392             year month date
 393             hour minute second
 394             (if daylight-p (1+ (- zone)) (- zone)))))
 395
 396 (defun cleanup-action-code (code)
 397   "Remove trailing newlines  so that the string CODE can be printed nicely."
 398   (subseq code 0
 399           (when (char= #\Newline (char code (1- (length code))))
 400             (1+ (position #\Newline code :from-end T :test #'char/=)))))
 401
 402 (defmacro checking-parse (grammarfile parse-file-fun)
 403   (let ((res (gensym "resultctx")))
 404     `(let ((,res (funcall ,parse-file-fun ,grammarfile *package*)))
 405       (cond
 406         ((ctx-failed-p ,res)
 407          (format *error-output* "Failed to parse PEG grammar ~A~%" ,grammarfile)
 408          (error "Parsing ~A failed: ~A" ,grammarfile ,res))
 409         ((< (end-index ,res) (length (input ,res)))
 410          (format *error-output* "Parsed only ~D characters of grammar ~A~%" (end-index ,res) ,grammarfile)
 411          ,res)
 412         (T ,res)))))
 413
 414 (defun generate-parser-file (grammarfile dst-package dst-file &key start-rule (parse-file-fun #'opossum:parse-file))
 415   "Create lisp code in DST-FILE that can be loaded to yield functions to parse using GRAMMARFILE in DST-PACKAGE.
 416 DST-PACKAGE will contain the 3 functions PARSE-STRING, PARSE-FILE and PARSE-STREAM as exported entrypoints."
 417   (let* ((*package* dst-package)
 418          (result (checking-parse grammarfile parse-file-fun))
 419          ;; FIXME: check for complete parse
 420          (*context* result)  ;; routines in pegutils.lisp expect *context* to be bound properly
 421          (dpkg (intern (package-name dst-package) :keyword)))
 422     (let ((forms (transform (value result)))
 423           (actions (actions result)))
 424       (with-open-file (s dst-file :direction :output :if-exists :supersede)
 425         (let ((*print-readably* T)
 426               (*print-pretty* T)
 427               (*print-circle* NIL))
 428           (format s ";; This is a Common Lisp peg parser automatically generated by OPOSSUM -*- mode:lisp -*-~%")
 429           (format s ";; generated from ~A on ~A~%" grammarfile (get-iso-time))
 430           (prin1 `(eval-when (:load-toplevel :compile-toplevel :execute)
 431                    (declaim (optimize (speed 0) (safety 3) (debug 3))))
 432                  s)
 433           (terpri s)
 434           (prin1 `(defpackage ,dpkg
 435                    (:use :cl :opossum)
 436                    (:export :parse-string :parse-file :parse-stream :*trace*))
 437                  s)
 438           (terpri s)
 439           (prin1 `(in-package ,dpkg) s) (terpri s)
 440           ;; First form is taken to be the start rule
 441           (let ((entryrule (or (and start-rule (make-name start-rule))
 442                                (and forms (cadr (first forms))))))
 443             (if (not entryrule)
 444                 (format *error-output* "Cannot find entry rule for parser")
 445                 (progn
 446                   (when *trace*
 447                     (format *trace-output* "Inserting definitions for parser entry points through ~A~%"
 448                             entryrule))
 449                   (terpri s)
 450                   (prin1 `(defun parse-string (,(intern :s dst-package) dst-package)
 451                            ,(format nil "Parse S using grammar ~A starting at ~A" grammarfile entryrule)
 452                            (let ((*context* (make-instance 'opossum:context
 453                                                            :dst-package dst-package
 454                                                            :input ,(intern :s dst-package))))
 455                              (funcall (,entryrule) 0)))
 456                          s)
 457                   (terpri s)
 458                   (prin1 `(defun parse-file (,(intern :f dst-package) dst-package)
 459                            ,(format nil "Parse file F using grammar ~A starting at ~A" grammarfile entryrule)
 460                            (parse-string (opossum:read-file ,(intern :f dst-package)) dst-package))
 461                          s)
 462                   (terpri s)
 463                   (prin1 `(defun parse-stream (,(intern :stream dst-package) dst-package)
 464                            ,(format nil "Parse stream F using grammar ~A starting at ~A" grammarfile entryrule)
 465                            (parse-string (opossum:read-stream ,(intern :stream dst-package)) dst-package))
 466                          s)
 467                   (fresh-line s))))
 468           (loop :for aform :in forms
 469                 :do (when *trace* (format *trace-output* "Inserting form ~A~%" aform))
 470                 :do (terpri s)
 471                 :do (prin1 aform s)
 472                 :do (fresh-line s))
 473           (terpri s)
 474           (prin1
 475            `(defparameter ,(intern "*trace*" dst-package) nil
 476              "When non-nil, the generated parser function log to cl:*trace-output*.")
 477            s)
 478           (terpri s)
 479
 480           (loop :for (sym code) :in actions
 481                 :when sym ;; the final action is named NIL because we push a
 482                 ;; NIL ahead of us in store-actions
 483                 :do (when *trace* (format *trace-output* "Inserting defun for ~A~%" sym))
 484                 :and :do (format s "~%(defun ~S (data)~% (declare (ignorable data) (type list data))~% ~A)~%"
 485                                  sym (cleanup-action-code code))))))))
 486
 487 (defun generate-parser-package (grammarfile &key (dst-package (make-package (gensym "opossum-parser-")))
 488                                 start-rule (parse-file-fun #'opossum:parse-file))
 489   "Create functions to parse using GRAMMARFILE in DST-PACKAGE, starting ar rule named HEAD.
 490 DST-PACKAGE will contain the 3 functions PARSE-STRING, PARSE-FILE and PARSE-STREAM as exported entrypoints."
 491   (let* ((*package* dst-package)
 492          (result (checking-parse grammarfile parse-file-fun))
 493          ;; FIXME: check for complete parse
 494          (*context* result)) ;; routines in pegutils.lisp expect *context* to be bound properly)
 495     (let ((forms (transform (value result)))
 496           (actions (actions result)))
 497       (format *trace-output* "Injecting parser functions into ~A~%" dst-package)
 498       (break "~A, ~A" forms actions)
 499       (use-package '(:cl :opossum) dst-package)
 500       (let ((entryrule (or (and start-rule (make-name start-rule))
 501                            (and forms (cadr (first forms))))))
 502         (if (not entryrule)
 503             (format *error-output* "Cannot find entry rule for parser")
 504             (progn
 505               (when *trace*
 506                 (format *trace-output* "Inserting definitions for parser entry points through ~A~%"
 507                         entryrule))
 508               (intern (compile 'parse-string
 509                                `(lambda (,(intern :s dst-package))
 510                                  ,(format nil "Parse S using grammar ~A starting at ~A" grammarfile entryrule)
 511                                  (let ((*context* (make-instance 'opossum:context
 512                                                                  :dst-package ,dst-package
 513                                                                  :input ,(intern :s dst-package))))
 514                                    (funcall (,entryrule) 0))))
 515                       dst-package)
 516               (intern (compile 'parse-file
 517                                `(lambda (,(intern :f dst-package))
 518                                  ,(format nil "Parse file F using grammar ~A starting at ~A" grammarfile entryrule)
 519                                  (parse-string (opossum:read-file ,(intern :f dst-package)))))
 520                       dst-package)
 521
 522               (intern (compile 'parse-stream
 523                                `(lambda (,(intern :stream dst-package))
 524                                  ,(format nil "Parse stream F using grammar ~A starting at ~A" grammarfile entryrule)
 525                                  (parse-string (opossum:read-stream ,(intern :stream dst-package)))))
 526                       dst-package))))
 527       (intern '*trace* dst-package)
 528       (setf (documentation '*trace* 'cl:variable)
 529             "When non-nil, the generated parser function log to cl:*trace-output*.")
 530       (export '(:parse-string :parse-file :parse-stream :*trace*) dst-package)
 531
 532       (loop :for aform :in forms
 533             :do (when *trace*
 534                   (format *trace-output* "Injecting form ~A~%" aform))
 535             :do (destructuring-bind (defun-sym name args &rest body)
 536                     aform
 537                   (declare (ignore defun-sym))
 538                   (intern (compile name `(lambda ,args ,@body)) dst-package)))
 539       (loop :for (sym code) :in actions
 540             :when sym
 541             :do (when *trace* (format *trace-output* "Injecting definition for ~A~%" sym))
 542             :and :do (intern (compile sym `(lambda (data) (declare (ignorable data)) ,code)) dst-package)))))
 543
 544
 545
 546 (defun transform (tree &optional (depth 0))
 547   (if (and tree
 548            (consp tree))
 549       (if (eq (first tree) ':action)
 550           (progn
 551             (when *trace*
 552               (format *trace-output* "~AFound action ~A~%"  (make-string depth :initial-element #\Space) tree))
 553             tree)
 554           (let ((data (mapcar #'(lambda (tr) (transform tr (1+ depth)))
 555                               tree)))
 556             (loop :for el :in data
 557                   :when (and (listp el)
 558                              (eq (first el) ':action)
 559                              (symbolp (third el)))
 560                   :do (let ((*package* (dst-package *context*))
 561                             (action (third el)))
 562                         (when *trace*
 563                           (format *trace-output* "~&Applying action ~A to ~A~%" action data))
 564                         (handler-case
 565                             (return-from transform
 566                               (funcall (symbol-function action) data))
 567                           (undefined-function (x)
 568                             (progn
 569                               (format *error-output* "missing definition for ~A: ~A~%" action x)
 570                               ;                       (break "~A in ~A" action *package*)
 571                                     tree)))))
 572             data))
 573       tree))