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(in-package #:parser)
(defun run (p input)
(let ((result (funcall p input)))
(if (parsing-p result)
(parsing-tree result)
result)))
(defstruct parsing
tree
left)
(defstruct failure
place
message)
(defmethod print-object ((obj failure) stream)
(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)))))
(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 crit (p)
(lambda (input)
(let ((r (funcall p input)))
(if (parsing-p r)
r
(error (format nil "~a" r))))))
(defun one-of (first-parser second-parser &rest other-parsers)
(lambda (input)
(labels ((one-of-rec (parsers failures)
(if (car parsers)
(let ((r (funcall (car parsers) input)))
(cond ((failure-p r)
(one-of-rec (cdr parsers) (cons r failures)))
((listp r)
(one-of-rec (cdr parsers) (append r failures)))
(t r)))
failures)))
(one-of-rec (cons first-parser (cons second-parser other-parsers)) nil))))
(defmacro unit (&optional predicate)
(cond ((null predicate)
(setf predicate '(characterp it)))
((symbolp predicate)
(setf predicate `(,predicate it)))
((characterp predicate)
(setf predicate `(char-equal ,predicate it)))
(t (setf predicate
(nsubst-if 'it
(lambda (x)
(and (symbolp x)
(string-equal (symbol-name x) "IT"))) predicate))))
`(lambda (input)
(if (input:has-data? input)
(let ((it (input:peek input)))
(if ,predicate
(make-parsing :tree it :left (input:advance input))
(make-failure :place input
:message (format nil "Expected: ~a, Got: ~a" ',predicate it))))
(make-failure :place input :message "Reached end of input."))))
(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-failure :place input :message "Predicate not satisfied."))
(make-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)))
(defparameter whitespace
(comp ((_ (optional (many (unit char:whitespace?)))))
nil))
(defun separated-list (p separator &key include-separator)
(comp ((v p)
(sep (optional separator))
(vn (if sep
(crit (separated-list p separator))
nothing)))
(if include-separator
(cons v (cons sep vn))
(cons v vn))))
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