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(in-package #:parser)
(defstruct parsing
tree
left)
(defmethod print-object ((obj parsing) stream)
(print-unreadable-object (obj stream :type t)
(format stream "~a" (parsing-tree obj))))
(defstruct failure
place
message)
(defmethod print-object ((obj failure) stream)
(print-unreadable-object (obj stream :type t)
(let ((file (input:file (failure-place obj))))
(if file
(multiple-value-bind (line column) (input:line-and-column (failure-place obj))
(format stream "~a:~a:~a: ~a" line column file (failure-message obj)))
(format stream "~a: ~a" (input:cursor (failure-place obj)) (failure-message obj))))))
(defstruct (normal-failure (:include failure)))
(defstruct (critical-failure (:include failure)))
(defun new (tree)
(lambda (input)
(make-parsing :tree tree :left input)))
(defun bind-with-input (p f)
(declare (optimize (speed 3)))
(declare (type function p f))
(lambda (input)
(let ((r (funcall p input)))
(if (parsing-p r)
(funcall (the function (funcall f (parsing-tree r) input))
(parsing-left r))
r))))
(defun bind (p f)
(declare (optimize (speed 3)))
(declare (type function p f))
(lambda (input)
(let ((r (funcall p input)))
(if (parsing-p r)
(funcall (the function (funcall f (parsing-tree r)))
(parsing-left r))
r))))
(defun discarding-bind (p f)
(declare (optimize (speed 3)))
(declare (type function p f))
(lambda (input)
(let ((r (funcall p input)))
(if (parsing-p r)
(funcall (the function (funcall f))
(parsing-left r))
r))))
(defmacro comp (bindings &body body)
(if (null bindings)
`(new (progn ,@body))
(let ((v (first (car bindings)))
(p (second (car bindings))))
(if (eq 'symbol (type-of v))
(if (string= (symbol-name v) "_")
`(discarding-bind ,p (lambda () (comp ,(cdr bindings) ,@body)))
`(bind ,p (lambda (,v) (comp ,(cdr bindings) ,@body))))
(if (and (eq 'cons (type-of v))
(eq 'symbol (type-of (car v)))
(eq 'symbol (type-of (cdr v))))
`(bind-with-input ,p (lambda (,(car v) ,(cdr v)) (comp ,(cdr bindings) ,@body)))
(error "Binding name/(name,input) must be either a symbol or a cons of symbols."))))))
(defun fail (&optional (message "Unknown error."))
(lambda (input)
(make-critical-failure :place input :message message)))
(defun one-of (first-parser second-parser &rest other-parsers)
(lambda (input)
(labels ((one-of-rec (body)
(if (cdr body)
(let ((r (funcall (car body) input)))
(if (normal-failure-p r)
(one-of-rec (cdr body))
r))
(funcall (car body) input))))
(one-of-rec (cons first-parser (cons second-parser other-parsers))))))
(defun all-of (first-parser second-parser &rest other-parsers)
(lambda (input)
(labels ((all-of-rec (body)
(if (cdr body)
(let ((r (funcall (car body) input)))
(if (parsing-p r)
(all-of-rec (cdr body))
r))
(funcall (car body) input))))
(all-of-rec (cons first-parser (cons second-parser other-parsers))))))
(defun negate (p)
(lambda (input)
(let ((r (funcall p input)))
(cond ((parsing-p r)
(make-normal-failure :place input :message "Negated parser result."))
((normal-failure-p r)
(make-parsing :tree nil :left input))
(t r)))))
(defun unit-if (&optional (predicate #'characterp))
(lambda (input)
(if (input:has-data? input)
(let ((c (input:peek input)))
(if (funcall predicate c)
(make-parsing :tree c :left (input:advance input))
(make-normal-failure :place input :message "Predicate not satisfied.")))
(make-normal-failure :place input :message "Reached end of input."))))
(defun unit (target)
(unit-if (lambda (x) (char= x target))))
(defun not-unit (target)
(unit-if (lambda (x) (char/= x target))))
(defun literal (target)
(lambda (input)
(if (input:has-data? input)
(if (input:prefix? target input)
(make-parsing :tree target :left (input:advance input (length target)))
(make-normal-failure :place input :message "Predicate not satisfied."))
(make-normal-failure :place input :message "Reached end of input."))))
(defun not-literal (target)
(lambda (input)
(if (input:has-data? input)
(if (input:prefix? target input)
(make-normal-failure :place input :message "Predicate not satisfied.")
(make-parsing :tree (input:peek input) :left (input:advance input)))
(make-normal-failure :place input :message "Reached end of input."))))
(defparameter nothing
(new nil))
(defun optional (p)
(one-of p nothing))
(defun many (p)
(comp ((x p)
(xs (optional (many p))))
(cons x xs)))
(defun separated-list (p separator &key (include-separator nil))
(comp ((v p)
(sep (optional separator))
(vn (if sep
(one-of (separated-list p separator)
(fail "Value expected."))
nothing)))
(if include-separator
(cons v (cons sep vn))
(cons v vn))))
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