;;; along with SOD; if not, write to the Free Software Foundation,
;;; Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
-(defun play (args)
- "Parse and evaluate a simple expression.
+;;;--------------------------------------------------------------------------
+;;; The expression parser.
+
+(flet ((dispatch (name args &rest spec)
+ (acond ((find :invalid args :key #'car)
+ (cons :invalid nil))
+ ((find-if (lambda (item)
+ (every (lambda (type arg)
+ (eql type (car arg)))
+ (cddr item)
+ args))
+ spec)
+ (cons (car it) (apply (cadr it)
+ (mapcar #'cdr args))))
+ (t
+ (cerror* "Type mismatch: operator `~A' applied to ~
+ types ~{~(~A~)~#[~; and ~;, ~]~}"
+ name
+ (mapcar #'car args))
+ (cons :invalid nil)))))
+ (let ((add (binop "+" (x y 5)
+ (dispatch "+" (list x y) (list :int #'+ :int :int))))
+ (sub (binop "-" (x y 5)
+ (dispatch "-" (list x y) (list :int #'- :int :int))))
+ (mul (binop "*" (x y 7)
+ (dispatch "*" (list x y) (list :int #'* :int :int))))
+ (div (binop "/" (x y 7)
+ (dispatch "/" (list x y)
+ (list :int
+ (lambda (x y)
+ (cond ((zerop y)
+ (cerror*
+ "Division by zero")
+ (cons :invalid nil))
+ (t
+ (floor x y))))
+ :int :int))))
+ (nop (preop "+" (x 9)
+ (dispatch "+" (list x) (list :int #'+ :int))))
+ (neg (preop "-" (x 9)
+ (dispatch "-" (list x) (list :int #'- :int))))
+ (lp (lparen #\)))
+ (rp (rparen #\))))
+
+ (defun parse-expression (scanner)
+ "Parse and evaluate a simple expression.
The result is a pair (TYPE . VALUE). Currently, type types are `:id',
- `:int', `:string', and `:char'. If an error prevented a sane ; value from
+ `:int', `:string', and `:char'. If an error prevented a sane value from
being produced, the type `:invalid' is returned.
The syntax of expressions is rather limited at the moment, but more may be
primary: int | id | string | `(' expression `)' | `?' lisp-expression
Only operators for dealing with integers are provided."
-
- (labels ((type-dispatch (name args &rest spec)
- (acond ((find :invalid args :key #'car)
- (cons :invalid nil))
- ((find-if (lambda (item)
- (every (lambda (type arg)
- (eql type (car arg)))
- (cddr item)
- args))
- spec)
- (cons (car it) (apply (cadr it)
- (mapcar #'cdr args))))
- (t
- (cerror* "Type mismatch: operator `~A' applied to ~
- types ~{~(~A~)~#[~; and ~;, ~]~}"
- name
- (mapcar #'car args))
- (cons :invalid nil))))
- (add (x y) (type-dispatch "+" (list x y)
- (list :integer #'+ :integer :integer)))
- (sub (x y) (type-dispatch "-" (list x y)
- (list :integer #'- :integer :integer)))
- (mul (x y) (type-dispatch "*" (list x y)
- (list :integer #'* :integer :integer)))
- (div (x y) (type-dispatch "/" (list x y)
- (list :integer
- (lambda (x y)
- (cond ((zerop y)
- (cerror*
- "Division by zero")
- (cons :invalid nil))
- (t
- (floor x y))))
- :integer :integer)))
- (nop (x) (type-dispatch "+" (list x)
- (list :integer #'+ :integer)))
- (neg (x) (type-dispatch "-" (list x)
- (list :integer #'- :integer))))
-
- (with-parser-context (token-scanner-context :scanner scanner)
- (parse (expr (lisp (flet ((prop (type value)
- (scanner-step scanner)
- (values (cons type value) t t)))
- (case (token-type scanner)
- (:int
- (prop :integer (token-value scanner)))
- ((:id :char :string)
- (prop (token-type scanner) (token-value scanner)))
- (#\?
- (let* ((stream (make-scanner-stream scanner))
- (sexp (read stream t)))
+ (with-parser-context (token-scanner-context :scanner scanner)
+ (parse (expr (:nestedp nestedp)
+ (lisp (flet ((prop (type value)
(scanner-step scanner)
- (values (cons (property-type sexp) sexp)
- t t)))
- (t
- (values (list :int :id :char :string #\?)
- nil nil)))))
+ (values (cons type value) t t)))
+ (case (token-type scanner)
+ ((:int :id :char :string)
+ (prop (token-type scanner)
+ (token-value scanner)))
+ (#\?
+ (let* ((stream (make-scanner-stream scanner))
+ (sexp (read stream t)))
+ (scanner-step scanner)
+ (values (cons (property-type sexp) sexp)
+ t t)))
+ (t
+ (values (list :int :id :char :string #\?)
+ nil nil)))))
+ (or (seq (#\+) add)
+ (seq (#\-) sub)
+ (seq (#\*) mul)
+ (seq (#\/) div))
+ (or (seq (#\() lp)
+ (seq (#\+) nop)
+ (seq (#\-) neg))
+ (when nestedp (seq (#\)) rp))))))))
+
+;;;--------------------------------------------------------------------------
+;;; Parsing property sets.
(defun parse-property (scanner pset)
"Parse a single property using the SCANNER; add it to the PSET."
- ;; id `=' expression
+ ;; property ::= id `=' expression
+ (with-parser-context (token-scanner-context :scanner scanner)
+ (parse (seq ((name :id) #\= (result (parse-expression scanner)))
+ (let ((type (car result))
+ (value (cdr result)))
+ (unless (eq type :invalid)
+ (add-property pset name value
+ :type type
+ :location scanner)))))))
+
+(export 'parse-property-set)
+(defun parse-property-set (scanner)
+ "Parse an optional property set from the SCANNER and return it, or `nil'."
+ ;; property-set ::= [`[' property-list `]']
+ (with-parser-context (token-scanner-context :scanner scanner)
+ (parse (? (seq (#\[
+ (pset (many (pset (make-property-set) pset)
+ (parse-property scanner pset)
+ #\,))
+ #\])
+ pset)))))
;;;----- That's all, folks --------------------------------------------------
~mdw / sod / blobdiff