Only operators for dealing with integers are provided."
- (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)))))
-
- (with-parser-context (token-scanner-context :scanner scanner)
- (parse (expr (:nestedp nestedp)
- (lisp (flet ((prop (type value)
- (scanner-step scanner)
- (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)
- (multiple-value-bind (type value)
- (restart-case (decode-property (eval sexp))
- (continue () (values :invalid nil)))
- (values (cons type value) t t))))
- (#\{
- (values (cons :fragment
- (parse-delimited-fragment scanner
- #\{ #\}))
- t t))
- (#\<
- (parse (seq (#\<
- (ds (parse-c-type scanner))
- (dc (parse-declarator
- scanner ds
- :kernel (lambda ()
- (values nil t nil))
- :abstractp t))
- #\>)
- (values (cons :type (car dc))
- t t))))
- (t
- (values (list :int :id :char :string #\? #\{ #\<)
- nil nil)))))
-
- ((:op #\* binop "*" (x y 7)
- (dispatch "*" (list x y) (list :int #'* :int :int)))
- (:op #\/ 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)))
- (:op #\+ binop "+" (x y 5)
- (dispatch "+" (list x y) (list :int #'+ :int :int)))
- (:op #\- binop "-" (x y 5)
- (dispatch "-" (list x y) (list :int #'- :int :int))))
-
- ((:op #\+ preop "+" (x 9)
- (dispatch "+" (list x) (list :int #'+ :int)))
- (:op #\- preop "-" (x 9)
- (dispatch "-" (list x) (list :int #'- :int)))
- (:op #\( lparen #\)))
-
- ((:op (when nestedp #\)) rparen #\))))))))
+ ;; The expression parser works in two stages. First, the parser proper
+ ;; builds a thunk as its `value'. If this is successful, then the thunk is
+ ;; invoked to return a property type and value. Primitive expressions
+ ;; produce thunks which just return their values; operators combine their
+ ;; argument thunks together, evaluating them (or not) on demand.
+
+ (macrolet ((oplambda (&body body)
+ ;; Like `lambda', but (a) always produces a function with no
+ ;; arguments, and (b) captures the current location so that
+ ;; errors are attributed correctly.
+
+ (with-gensyms (floc)
+ `(let ((,floc (file-location scanner)))
+ (lambda ()
+ (with-default-error-location (,floc)
+ ,@body))))))
+
+ (labels ((want (type thunk)
+ ;; Evaluate THUNK and convert its result to the given TYPE.
+ (multiple-value-bind (ty val) (funcall thunk)
+ (coerce-property-value val ty type)))
+
+ (int-unop (intop x)
+ ;; Evaluate X to an integer, and apply INTOP to the result,
+ ;; giving another integer.
+ (oplambda (values :int (funcall intop (want :int x)))))
+
+ (int-binop (intop x y)
+ ;; Evaluate X and Y to integers, and apply INTOP to the
+ ;; results, giving another integer.
+ (oplambda
+ (values :int (funcall intop (want :int x) (want :int y)))))
+
+ (compareop (intop strop x y)
+ ;; Evaluate X and Y. If they're integers, then apply INTOP to
+ ;; them; if they're strings, apply STROP. The result is a
+ ;; boolean.
+ (oplambda
+ (multiple-value-bind (xty xval) (funcall x)
+ (case xty
+ (:int
+ (values :boolean
+ (funcall intop xval (want :int y))))
+ ((:id :string :symbol)
+ (values :boolean
+ (funcall strop
+ (coerce-property-value xval xty :id)
+ (want :id y))))
+ (t
+ (error "Can't compare objects of type ~(~A~)" xty)))))))
+
+ (with-parser-context (token-scanner-context :scanner scanner)
+ (when-parse ()
+
+ ;; Parse the expression, producing a thunk.
+ (expr (:nestedp nestedp)
+
+ (lisp (case (token-type scanner)
+
+ ((:int :id :char :string)
+ ;; A simple literal.
+ (let ((type (token-type scanner))
+ (value (token-value scanner)))
+ (scanner-step scanner)
+ (values (lambda () (values type value)) t t)))
+
+ (#\?
+ ;; A Lisp s-expression. Catch and report reader-
+ ;; errors (though the main parser will probably
+ ;; end up /very/ confused); delay evaluation for
+ ;; later.
+ (handler-case
+ (let* ((stream (make-scanner-stream scanner))
+ (sexp (read stream t)))
+ (scanner-step scanner)
+ (values (oplambda (decode-property (eval sexp)))
+ t t))
+ (error (cond)
+ (scanner-step scanner)
+ (cerror*-with-location scanner
+ "Lisp `read' error: ~A"
+ cond)
+ (values #'continue t t))))
+
+ (#\{
+ ;; A code fragment.
+ (let ((fragment (parse-delimited-fragment scanner
+ #\{ #\})))
+ (values (lambda () (values :fragment fragment))
+ t t)))
+
+ (#\<
+ ;; A C type.
+ (parse (seq (#\<
+ (ds (parse-c-type scanner))
+ (dc (parse-declarator
+ scanner ds
+ :kernel (lambda ()
+ (values nil t nil))
+ :abstractp t))
+ #\>)
+ (values (lambda () (values :type (car dc)))
+ t t))))
+
+ (t
+ ;; Anything else is an error.
+ (values (list :int :id :char :string #\? #\{ #\<)
+ nil nil))))
+
+ ;; Binary operators.
+ ((:op #\* binop "*" (x y 70) (int-binop #'* x y))
+ (:op #\/ binop "/" (x y 70)
+ (oplambda
+ (let ((x (want :int x)) (y (want :int y)))
+ (when (zerop y) (error "Division by zero"))
+ (values :int (floor x y)))))
+ (:op #\+ binop "+" (x y 60) (int-binop #'+ x y))
+ (:op #\- binop "-" (x y 60) (int-binop #'- x y))
+ (:op :shl binop "<<" (x y 50) (int-binop #'ash x y))
+ (:op :shr binop ">>" (x y 50)
+ (int-binop (lambda (x y) (ash x (- y))) x y))
+ (:op #\< binop "<" (x y 45)
+ (compareop #'< #'string< x y))
+ (:op :le binop "<=" (x y 45)
+ (compareop #'<= #'string<= x y))
+ (:op :ge binop ">=" (x y 45)
+ (compareop #'>= #'string>= x y))
+ (:op #\> binop ">" (x y 45)
+ (compareop #'> #'string> x y))
+ (:op :eq binop "==" (x y 40)
+ (compareop #'= #'string= x y))
+ (:op :ne binop "!=" (x y 40)
+ (compareop #'/= #'string/= x y))
+ (:op #\& binop "&" (x y 37) (int-binop #'logand x y))
+ (:op #\^ binop "^" (x y 35) (int-binop #'logxor x y))
+ (:op #\| binop "|" (x y 32) (int-binop #'logior x y))
+ (:op :and binop "&&" (x y 27)
+ (oplambda (if (want :boolean x) (funcall y)
+ (values :boolean nil))))
+ (:op :or binop "||" (x y 22)
+ (oplambda
+ (multiple-value-bind (xty xval) (funcall x)
+ (if (coerce-property-value xval xty :boolean)
+ (values xty xval)
+ (funcall y))))))
+
+ ;; Prefix operators.
+ ((:op #\~ preop "~" (x 90) (int-unop #'lognot x))
+ (:op #\! preop "!" (x 90)
+ (oplambda
+ (values :boolean
+ (not (want :boolean (funcall x))))))
+ (:op #\+ preop "+" (x 90) (int-unop #'identity x))
+ (:op #\- preop "-" (x 90) (int-unop #'- x))
+ (:op #\( lparen #\)))
+
+ ;; Postfix operators.
+ ((:op (when nestedp #\)) rparen #\))))
+
+ ;; Do the delayed evaluation. Establish a restart so that we can
+ ;; continue if evaluation fails for some reason. (The value thunk
+ ;; is expected to report the correct error locations, if it signals
+ ;; conditions.)
+ (restart-case (multiple-value-bind (type value) (funcall it)
+ (values (cons type value) t t))
+ (continue () (values (cons :invalid nil) t t))))))))
;;;--------------------------------------------------------------------------
;;; Parsing property sets.
~mdw / sod / blobdiff