Created
October 25, 2014 14:06
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Common Lisp utilities for parsing a sequence
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(in-package :cl-user) | |
(defpackage parser-utils | |
(:use :cl) | |
(:import-from :alexandria | |
:with-gensyms) | |
(:export :with-array-parsing | |
:redo | |
:gonext | |
:goto)) | |
(in-package :parser-utils) | |
(define-condition parsing-end-unexpectedly (simple-error) | |
((state :initarg :state | |
:initform nil)) | |
(:report (lambda (condition stream) | |
(format stream "Parsing ended unexpectedly~:[~;~:* at ~A~]" | |
(slot-value condition 'state))))) | |
(define-condition no-next-state (simple-error) ()) | |
(defmacro with-array-parsing ((elem p seq &optional (start 0) end) &body body) | |
(with-gensyms (g-end no-next-state last) | |
(let ((eof-exists nil)) | |
`(let ((,p ,start) | |
(,g-end (locally (declare #+sbcl (sb-ext:muffle-conditions sb-ext:compiler-note)) | |
(or ,end (length ,seq)))) | |
,elem) | |
(declare (ignorable ,p ,g-end ,elem)) | |
(macrolet ((goto (tag &optional (amount 1)) | |
`(progn | |
(incf ,',p ,amount) | |
,@(if (eql amount 0) | |
() | |
`((when (= ,',p ,',g-end) | |
(go :eof)) | |
(setq ,',elem (aref ,',seq ,',p)))) | |
(go ,tag)))) | |
(tagbody | |
(when (= ,p ,g-end) | |
(go :eof)) | |
(setq ,elem (aref ,seq ,p)) | |
,@(loop for (tagpart . rest) on body | |
for (tag . part) = tagpart | |
if (eq tag :eof) | |
append (progn | |
(setf eof-exists t) | |
`(,@tagpart | |
(go ,last))) | |
else | |
append | |
(list tag | |
`(macrolet ((redo (&optional (amount 1)) | |
`(goto ,',tag ,amount)) | |
(gonext (&optional (amount 1)) | |
`(goto ,',(or (caar rest) no-next-state) | |
,amount))) | |
,@part | |
(error 'parsing-end-unexpectedly :state ',tag)))) | |
,no-next-state | |
(error 'no-next-state) | |
,@(if eof-exists | |
() | |
'(:eof)) | |
,last)))))) |
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