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(in-package :parser-combinators)
(defmacro define-oneshot-result (inp is-unread &body body)
`(function (lambda (,inp)
(let ((,is-unread t))
#'(lambda ()
(when ,is-unread
(setf ,is-unread nil)
,@body))))))
(declaim (inline sat))
(def-cached-arg-parser sat (predicate)
"Parser: return a token satisfying a predicate."
#'(lambda (inp)
(typecase inp
(end-context (constantly nil))
(context
(if (funcall predicate (context-peek inp))
(let ((closure-value
(make-instance 'parser-possibility
:tree (context-peek inp) :suffix (context-next inp))))
#'(lambda ()
(when closure-value
(prog1
closure-value
(setf closure-value nil)))))
(constantly nil))))))
(def-cached-arg-parser char? (character)
"Parser: accept token eql to argument"
(sat (curry #'eql character)))
(def-cached-arg-parser char-equal? (character)
"Parser: accept token char-equal to argument"
(sat (curry #'char-equal character)))
(defgeneric string?-using-context (input vector test)
(:documentation "Implementation of string? specialized on context type. Returns as multiple
values result and new context or nil on failure.")
(:method ((input context) vector test)
(iter (for c in-vector vector)
(for inp-iter initially input then (context-next inp-iter))
(when (end-context-p inp-iter)
(return nil))
(for inp-data = (context-peek inp-iter))
(unless (funcall test c inp-data)
(return (values nil nil)))
(finally (return
(values (context-interval input inp-iter)
inp-iter)))))
(:method ((input vector-context) vector test)
(check-type vector vector)
(let ((input-vector (storage-of input))
(l (length vector))
(p (position-of input)))
(check-type input-vector vector)
(if (> (+ l p)
(length input-vector))
(values nil nil)
(let ((mismatch (mismatch input-vector vector
:test test
:start1 p
:end1 (+ p l))))
(if mismatch
(values nil nil)
(values (subseq input-vector p (+ p l))
(if (= (+ p l) (length input-vector))
(make-instance 'end-context
:common (common-of input)
:position (+ p l))
(make-instance 'vector-context
:common (common-of input)
:position (+ p l))))))))))
(def-cached-arg-parser string? (sequence &key (test #'eql) (result-type 'string))
"Non-backtracking parser: accept a sequence of elements with equality tested by TEST."
(let ((vector (coerce sequence 'vector)))
(define-oneshot-result inp is-unread
(multiple-value-bind (result new-input)
(string?-using-context inp vector test)
(when new-input
(make-instance 'parser-possibility
:tree (coerce result result-type)
:suffix new-input))))))
(defun ensure-parser (parser)
(typecase parser
(function parser)
(list (if (cdr parser)
(string? parser)
(char? (car parser))))
(vector (if (length= 1 parser)
(char? (aref parser 0))
(string? parser)))
(t (char? parser))))
(defmacro with-parsers ((&rest parsers) &body body)
`(let ,(iter (for p in parsers)
(collect `(,p (ensure-parser ,p))))
,@body))
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