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(in-package #:monparser)
(defstruct parsing
tree
left
limit)
(defstruct failure
place
message)
(defun lazy-parsing-p (r)
(or (functionp r)
(parsing-p r)))
(defun new (tree)
(lambda (input &key limit lazy)
(declare (ignore lazy))
(if (and limit (> limit 0))
(make-failure :place input
:message (format nil "Didn't reach expected limit: ~a." limit))
(make-parsing :tree tree :left input))))
(defun bind (p f &key (greedy t))
(lambda (input &key limit lazy)
(let (r)
(if greedy
(setf r (funcall p input :limit limit))
(let ((next-parser (funcall f nil input))
(limit -1))
(do ((sweep-input input (advance sweep-input)))
((or (not (has-data? sweep-input))
(> limit -1)) nil)
(when (lazy-parsing-p (funcall next-parser sweep-input :lazy t))
(setf limit (cursor-distance sweep-input input))))
(if (< limit 0)
(setf r (make-failure :place input
:message "Reached end of input while sweeping."))
(setf r (funcall p input :limit limit)))))
(if (parsing-p r)
(if lazy
(lambda (ignored-input &key lazy limit)
(declare (ignore ignored-input limit))
(funcall (funcall f (parsing-tree r) input)
(parsing-left r)
:lazy lazy
:limit (if greedy (parsing-limit r))))
(funcall (funcall f (parsing-tree r) input)
(parsing-left r)
:limit (if greedy (parsing-limit r))))
r))))
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