| 1 | ;;; -*-lisp-*- |
| 2 | ;;; |
| 3 | ;;; Parsers for expressions with binary operators |
| 4 | ;;; |
| 5 | ;;; (c) 2009 Straylight/Edgeware |
| 6 | ;;; |
| 7 | |
| 8 | ;;;----- Licensing notice --------------------------------------------------- |
| 9 | ;;; |
| 10 | ;;; This file is part of the Sensble Object Design, an object system for C. |
| 11 | ;;; |
| 12 | ;;; SOD is free software; you can redistribute it and/or modify |
| 13 | ;;; it under the terms of the GNU General Public License as published by |
| 14 | ;;; the Free Software Foundation; either version 2 of the License, or |
| 15 | ;;; (at your option) any later version. |
| 16 | ;;; |
| 17 | ;;; SOD is distributed in the hope that it will be useful, |
| 18 | ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 19 | ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 20 | ;;; GNU General Public License for more details. |
| 21 | ;;; |
| 22 | ;;; You should have received a copy of the GNU General Public License |
| 23 | ;;; along with SOD; if not, write to the Free Software Foundation, |
| 24 | ;;; Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 25 | |
| 26 | (cl:in-package #:sod-parser) |
| 27 | |
| 28 | ;;;-------------------------------------------------------------------------- |
| 29 | ;;; Basic protocol implementation. |
| 30 | |
| 31 | (defclass expression-parse-state () |
| 32 | ((opstack :initform nil :type list) |
| 33 | (valstack :initform nil :type list) |
| 34 | (nesting :initform 0 :type fixnum)) |
| 35 | (:documentation |
| 36 | "State for the expression parser. Largely passive.")) |
| 37 | |
| 38 | (defmethod push-value (value (state expression-parse-state)) |
| 39 | (with-slots (valstack) state |
| 40 | (push value valstack))) |
| 41 | |
| 42 | (defmethod push-operator (operator (state expression-parse-state)) |
| 43 | (with-slots (opstack) state |
| 44 | (loop |
| 45 | (when (null opstack) (return)) |
| 46 | (let ((head (car opstack))) |
| 47 | (ecase (operator-push-action head operator) |
| 48 | (:push (return)) |
| 49 | (:error (cerror* "Parse error: ... ~A ... ~A ... forbidden; ~ |
| 50 | operators aren't associative" |
| 51 | head operator)) |
| 52 | (:apply (apply-operator head state) |
| 53 | (setf opstack (cdr opstack)))))) |
| 54 | (push operator opstack))) |
| 55 | |
| 56 | (defgeneric apply-pending-operators (state) |
| 57 | (:documentation |
| 58 | "Apply all of the pending operators to their arguments. |
| 59 | |
| 60 | The return value is the final result of the parse. By the time all of the |
| 61 | operators have been applied, of course, there ought to be exactly one |
| 62 | operand remaining.") |
| 63 | (:method ((state expression-parse-state)) |
| 64 | (with-slots (opstack valstack) state |
| 65 | (dolist (operator opstack) |
| 66 | (apply-operator operator state)) |
| 67 | (assert (and (consp valstack) (null (cdr valstack)))) |
| 68 | (pop valstack)))) |
| 69 | |
| 70 | ;;;-------------------------------------------------------------------------- |
| 71 | ;;; Basic operator implementation. |
| 72 | |
| 73 | (defmethod operator-push-action (left right) |
| 74 | (let ((lprec (operator-right-precedence left)) |
| 75 | (rprec (operator-left-precedence right))) |
| 76 | (cond ((< lprec rprec) :push) |
| 77 | ((> lprec rprec) :apply) |
| 78 | (t (let ((lassoc (operator-associativity left)) |
| 79 | (rassoc (operator-associativity right))) |
| 80 | (cond ((not (eq lassoc rassoc)) |
| 81 | (cerror* "Parse error: ... ~A ... ~A ...: ~ |
| 82 | inconsistent associativity: ~ |
| 83 | ~(~A~) versus ~(~A~))" |
| 84 | left right |
| 85 | (or lassoc "none") (or rassoc "none")) |
| 86 | :apply) |
| 87 | ((not lassoc) |
| 88 | (cerror* "Parse error: ... ~A ... ~A ...: ~ |
| 89 | operators are not associative" |
| 90 | left right) |
| 91 | :apply) |
| 92 | ((eq lassoc :left) :apply) |
| 93 | ((eq lassoc :right) :push) |
| 94 | (t (error "Invalid associativity ~S ~ |
| 95 | for operators ~A and ~A" |
| 96 | lassoc left right)))))))) |
| 97 | |
| 98 | (defmethod print-object ((operator simple-operator) stream) |
| 99 | (maybe-print-unreadable-object (operator stream :type t) |
| 100 | (princ (operator-name operator) stream))) |
| 101 | |
| 102 | (defmethod shared-initialize :after |
| 103 | ((operator simple-binary-operator) slot-names &key) |
| 104 | (when (slot-boundp operator 'lprec) |
| 105 | (default-slot (operator 'rprec slot-names) |
| 106 | (slot-value operator 'lprec)))) |
| 107 | |
| 108 | (defmethod push-operator |
| 109 | ((operator prefix-operator) (state expression-parse-state)) |
| 110 | |
| 111 | ;; It's not safe to apply stacked operators here. Already-stacked prefix |
| 112 | ;; operators won't have their operands yet, so we'll end up in an |
| 113 | ;; inconsistent state. |
| 114 | (with-slots (opstack) state |
| 115 | (push operator opstack))) |
| 116 | |
| 117 | (defmethod apply-operator |
| 118 | ((operator simple-unary-operator) (state expression-parse-state)) |
| 119 | (with-slots ((function %function)) operator |
| 120 | (with-slots (valstack) state |
| 121 | (assert (not (null valstack))) |
| 122 | (push (funcall function (pop valstack)) valstack)))) |
| 123 | |
| 124 | (defmethod apply-operator |
| 125 | ((operator simple-binary-operator) (state expression-parse-state)) |
| 126 | (with-slots ((function %function)) operator |
| 127 | (with-slots (valstack) state |
| 128 | (assert (not (or (null valstack) |
| 129 | (null (cdr valstack))))) |
| 130 | (let ((second (pop valstack)) |
| 131 | (first (pop valstack))) |
| 132 | (push (funcall function first second) valstack))))) |
| 133 | |
| 134 | ;;;-------------------------------------------------------------------------- |
| 135 | ;;; Parenthesis protocol implementation. |
| 136 | |
| 137 | (defmethod push-operator :after |
| 138 | ((paren open-parenthesis) (state expression-parse-state)) |
| 139 | (with-slots (nesting) state |
| 140 | (incf nesting))) |
| 141 | |
| 142 | (defmethod push-operator |
| 143 | ((paren close-parenthesis) (state expression-parse-state)) |
| 144 | (with-slots (opstack nesting) state |
| 145 | (with-slots (tag) paren |
| 146 | (flet ((fail () |
| 147 | (cerror* "Parse error: spurious `~A'" tag) |
| 148 | (return-from push-operator))) |
| 149 | (loop |
| 150 | (when (null opstack) (fail)) |
| 151 | (let ((head (car opstack))) |
| 152 | (cond ((not (typep head 'open-parenthesis)) |
| 153 | (apply-operator head state)) |
| 154 | ((not (eq (slot-value head 'tag) tag)) |
| 155 | (fail)) |
| 156 | (t |
| 157 | (return))) |
| 158 | (setf opstack (cdr opstack)))) |
| 159 | (setf opstack (cdr opstack)) |
| 160 | (decf nesting))))) |
| 161 | |
| 162 | (defmethod apply-operator |
| 163 | ((paren open-parenthesis) (state expression-parse-state)) |
| 164 | (with-slots (tag) paren |
| 165 | (cerror* "Parse error: missing `~A'" tag))) |
| 166 | |
| 167 | (defmethod operator-push-action (left (right open-parenthesis)) |
| 168 | (declare (ignore left)) |
| 169 | :push) |
| 170 | |
| 171 | (defmethod operator-push-action ((left open-parenthesis) right) |
| 172 | (declare (ignore right)) |
| 173 | :push) |
| 174 | |
| 175 | ;;;-------------------------------------------------------------------------- |
| 176 | ;;; Main expression parser implementation. |
| 177 | |
| 178 | (defun parse-expression (p-operand p-binop p-preop p-postop) |
| 179 | "Parse an expression consisting of operands and various kinds of operators. |
| 180 | |
| 181 | The arguments are all parser functions: they will be called with one |
| 182 | argument NESTEDP, which indicates whether the parse has encountered an |
| 183 | unmatched parenthesis." |
| 184 | |
| 185 | (let ((state (make-instance 'expression-parse-state)) |
| 186 | (consumed-any-p nil)) |
| 187 | |
| 188 | (labels ((fail (expected) |
| 189 | (return-from parse-expression |
| 190 | (values expected nil consumed-any-p))) |
| 191 | |
| 192 | (parse (parser) |
| 193 | (unless parser |
| 194 | (return-from parse (values nil nil))) |
| 195 | (multiple-value-bind (value winp consumedp) |
| 196 | (funcall parser (plusp (slot-value state 'nesting))) |
| 197 | (when consumedp (setf consumed-any-p t)) |
| 198 | (unless (or winp (not consumedp)) (fail value)) |
| 199 | (values value winp))) |
| 200 | |
| 201 | (get-operand () |
| 202 | (loop (multiple-value-bind (value winp) (parse p-preop) |
| 203 | (unless winp (return)) |
| 204 | (push-operator value state))) |
| 205 | (multiple-value-bind (value winp) (parse p-operand) |
| 206 | (unless winp (fail value)) |
| 207 | (push-value value state)) |
| 208 | (loop (multiple-value-bind (value winp) (parse p-postop) |
| 209 | (unless winp (return)) |
| 210 | (push-operator value state))))) |
| 211 | |
| 212 | (get-operand) |
| 213 | (loop |
| 214 | (multiple-value-bind (value winp) (parse p-binop) |
| 215 | (unless winp (return)) |
| 216 | (push-operator value state)) |
| 217 | (get-operand)) |
| 218 | |
| 219 | (values (apply-pending-operators state) t consumed-any-p)))) |
| 220 | |
| 221 | ;;;----- That's all, folks -------------------------------------------------- |