Source Code Cross Referenced for Term.java in  » Testing » KeY » de » uka » ilkd » key » logic » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Testing » KeY » de.uka.ilkd.key.logic 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        // This file is part of KeY - Integrated Deductive Software Design
002:        // Copyright (C) 2001-2007 Universitaet Karlsruhe, Germany
003:        //                         Universitaet Koblenz-Landau, Germany
004:        //                         Chalmers University of Technology, Sweden
005:        //
006:        // The KeY system is protected by the GNU General Public License. 
007:        // See LICENSE.TXT for details.
008:        //
009:        //
010:
011:        package de.uka.ilkd.key.logic;
012:
013:        import de.uka.ilkd.key.logic.op.*;
014:        import de.uka.ilkd.key.logic.sort.Sort;
015:        import de.uka.ilkd.key.util.Debug;
016:
017:        /** 
018:         * In contrast to the distinction of formulas and terms as made by most of the 
019:         * inductive definition of the syntax of a logic, an instance of this class can
020:         * stand for a term or a formula. This is done for implementation reasons, as
021:         * their structure is quite similar and there are good reasons concerning the
022:         * software's design/architecture (for example using same visitors, reduction of
023:         * case distinction, unified interfaces etc.). However, they are strictly
024:         * separated by their sorts. A formula (and just a formula) must have 
025:         * the sort {@link Sort#FORMULA}. Terms of a different sort are terms in the
026:         * customary logic sense. A term of sort formula is allowed exact there, where a
027:         * formuala in logic is allowed to appear, same for terms of different sorts. 
028:         *   Some words about other design decisions: 
029:         * <ol> 
030:         *  <li> terms are immutable, this means after a term object is created, it
031:         *  cannot be changed. The advantage is that we can use term sharing and
032:         *  saving a lot of memory space. 
033:         *  </li>
034:         *  <li> Term has to be created using the {@link TermFactory} and
035:         *    <emph>not</emph> by using the constructors itself. 
036:         *  </li>
037:         *  <li> Term is subclassed, but all subclasses have to be package private, so
038:         *    that all other classes except {@link TermFactory} know only the class
039:         *    Term and its interface. Even most classes of the logic package.
040:         *  </li>
041:         *  <li> as it is immutable, most (all) attributes should be declared final
042:         * </li>
043:         * </ol>
044:         * Term supports the {@link Visitor} pattern. Two different visit strategies are
045:         * currently supported: {@link Term#execPostOrder(Visitor)} and
046:         * {@link Term#execPreOrder(Visitor)}. 
047:         */
048:        public abstract class Term implements  SVSubstitute {
049:
050:            /** empty list of variables */
051:            public static final ArrayOfQuantifiableVariable EMPTY_VAR_LIST = new ArrayOfQuantifiableVariable(
052:                    new QuantifiableVariable[0]);
053:
054:            /** the top level operator of this term */
055:            private final Operator op;
056:
057:            /** caches the sort of this term */
058:            private final Sort sort;
059:
060:            /** caches the hashcode of the term */
061:            private int hashcode;
062:
063:            /** true iff this term is rigid */
064:            private boolean rigid;
065:
066:            /** 
067:             * caches the free variables of this term  
068:             */
069:            protected SetOfQuantifiableVariable freeVars = SetAsListOfQuantifiableVariable.EMPTY_SET;
070:
071:            /** caches the meta variables of this term */
072:            protected SetOfMetavariable metaVars = SetAsListOfMetavariable.EMPTY_SET;
073:
074:            /** 
075:             * creates a Term with top operator op
076:             * @param op Operator at the top of the termstructure that starts
077:             * here.
078:             * @param sort the Sort of the term
079:             */
080:            protected Term(Operator op, Sort sort) {
081:                this .op = op;
082:                this .sort = sort;
083:            }
084:
085:            /**
086:             * returns the arity of the term  
087:             * @return arity of the term 
088:             * */
089:            public abstract int arity();
090:
091:            protected int calculateHash() {
092:                int hashValue = 5;
093:                hashValue = hashValue * 17 + op().hashCode();
094:                hashValue = hashValue * 17 + sort().hashCode();
095:
096:                for (int i = 0, ar = arity(); i < ar; i++) {
097:                    hashValue = hashValue * 17 + varsBoundHere(i).size();
098:                    hashValue = hashValue * 17 + sub(i).hashCode();
099:                }
100:                hashValue = hashValue * 17 + javaBlock().hashCode();
101:                if (hashValue == 0)
102:                    return 1;
103:
104:                return hashValue;
105:            }
106:
107:            /**
108:             * checks whether the Term is valid on the top level. If this is
109:             * the case this method returns the Term unmodified. Otherwise a
110:             * TermCreationException is thrown.  
111:             * @return this Term if the top level of the Term is valid.
112:             */
113:            public Term checked() {
114:                if (op().validTopLevel(this )) {
115:                    return this ;
116:                } else {
117:                    throw new TermCreationException(op(), this );
118:                }
119:            }
120:
121:            /** 
122:             * returns the longest path from the top of the term to one of its leaves
123:             * @return an int representing the depth of this term
124:             */
125:            public abstract int depth();
126:
127:            /**
128:             * this method has to be called by subclasses after they determined the
129:             * arity of the term. The method then can determine the free vars of the
130:             * term and put them in a cache.
131:             */
132:            private void determineFreeVars() {
133:                for (int i = 0, ar = arity(); i < ar; i++) {
134:                    if (sub(i) == null) {
135:                        Debug.fail("FREE " + op + " " + i);
136:                    }
137:                    SetOfQuantifiableVariable subFreeVars = sub(i).freeVars;
138:                    for (int j = 0, sz = varsBoundHere(i).size(); j < sz; j++) {
139:                        subFreeVars = subFreeVars.remove(varsBoundHere(i)
140:                                .getQuantifiableVariable(j));
141:                    }
142:                    freeVars = freeVars.union(subFreeVars);
143:                }
144:            }
145:
146:            /**
147:             * computes the metavariables that are part of this term     
148:             */
149:            private void determineMetaVars() {
150:                for (int i = 0, ar = arity(); i < ar; i++) {
151:                    if (sub(i) == null) {
152:                        Debug.fail("FREE " + op + " " + i);
153:                    }
154:                    metaVars = metaVars.union(sub(i).metaVars);
155:                }
156:            }
157:
158:            /**
159:             * this method has to be called by subclasses after they have
160:             * assigned the subterms of the term. The method then can
161:             * determine whether the operator and the subterms are rigid and
162:             * put this information in a cache.
163:             *
164:             * the implementation of this method uses the fact that
165:             * quantifiable variables are rigid; otherwise, the results are
166:             * too pessimistic (but still valid)
167:             */
168:            private void determineRigidness() {
169:                this .rigid = op().isRigid(this );
170:            }
171:
172:            /**
173:             * true if <code>o</code> is syntactical equal to this term
174:             * @param o the Object to be compared with this term
175:             * @return true iff the given Term has the same values in
176:             * operator, sort, arity, varsBoundHere and javaBlock as this object.
177:             */
178:            public boolean equals(Object o) {
179:                if (o == null)
180:                    return false;
181:                if (o == this )
182:                    return true;
183:                if (!(o instanceof  Term))
184:                    return false;
185:
186:                final Term t = (Term) o;
187:
188:                if (!(t.hashCode() == hashCode() && sort() == t.sort()
189:                        && arity() == t.arity() && op().equals(t.op()) && javaBlock()
190:                        .equals(t.javaBlock()))) {
191:                    return false;
192:                }
193:
194:                for (int i = 0, ar = arity(); i < ar; i++) {
195:                    if (varsBoundHere(i).size() != t.varsBoundHere(i).size()) {
196:                        return false;
197:                    }
198:                    for (int j = 0, sz = varsBoundHere(i).size(); j < sz; j++) {
199:                        if (!varsBoundHere(i).getQuantifiableVariable(j)
200:                                .equals(
201:                                        t.varsBoundHere(i)
202:                                                .getQuantifiableVariable(j))) {
203:                            return false;
204:                        }
205:                    }
206:
207:                    if (!sub(i).equals(t.sub(i))) {
208:                        return false;
209:                    }
210:                }
211:
212:                return true;
213:            }
214:
215:            /**
216:             * compares if two terms are equal modulo bound renaming
217:             * @return true iff the given Term has the same values in
218:             * operator, sort, arity, varsBoundHere and javaBlock as this object
219:             * modulo bound renaming
220:             */
221:            public boolean equalsModRenaming(Object o) {
222:                if (o == null || !(o instanceof  Term)) {
223:                    return false;
224:                }
225:                if (o == this ) {
226:                    return true;
227:                }
228:                Term cmp = (Term) o;
229:                final Constraint result = Constraint.BOTTOM.unify(this , cmp,
230:                        null);
231:
232:                return result == Constraint.BOTTOM;
233:            }
234:
235:            /** 
236:             * the visitor is handed through till the bottom of the tree and
237:             * then it walks upwards while at each upstep the method visit of
238:             * the visitor is called
239:             * @param visitor the Visitor
240:             */
241:            public void execPostOrder(Visitor visitor) {
242:                visitor.subtreeEntered(this );
243:                for (int i = 0, ar = arity(); i < ar; i++) {
244:                    sub(i).execPostOrder(visitor);
245:                }
246:                visitor.visit(this );
247:                visitor.subtreeLeft(this );
248:            }
249:
250:            /** the visitor walks downwards the tree
251:             * while at each downstep the method visit of
252:             * the visitor is called
253:             * @param visitor the Visitor
254:             */
255:            public void execPreOrder(Visitor visitor) {
256:                visitor.subtreeEntered(this );
257:                visitor.visit(this );
258:                for (int i = 0, ar = arity(); i < ar; i++) {
259:                    sub(i).execPreOrder(visitor);
260:                }
261:                visitor.subtreeLeft(this );
262:            }
263:
264:            /** 
265:             * The primary diamond in this formula. Note that the default
266:             * implementation is the same as <code>javaBlock()</code> but
267:             * the semantics is different. See <code>SimultaneousUpdateTerm</code>.
268:             */
269:            public JavaBlock executableJavaBlock() {
270:                return javaBlock();
271:            }
272:
273:            /**
274:             * fills the cache variables
275:             * must be called in the constructors 
276:             */
277:            protected void fillCaches() {
278:                determineFreeVars();
279:                determineMetaVars();
280:                determineRigidness();
281:                hashcode = calculateHash();
282:            }
283:
284:            /** 
285:             * returns the set of free quantifiable variables occuring in this term
286:             * @return the SetOfFree 
287:             */
288:            public SetOfQuantifiableVariable freeVars() {
289:                return freeVars;
290:            }
291:
292:            /**
293:             * returns the hashcode of the term
294:             * @return the hashcode of the Term.
295:             */
296:            public int hashCode() {
297:                if (hashcode == 0) {
298:                    hashcode = calculateHash();
299:                }
300:                return hashcode;
301:            }
302:
303:            /**
304:             * @return true iff all subterms of this term are rigid according
305:             * to the value the method "isRigid" returns for them (this does
306:             * not imply this term to be rigid itself!)
307:             */
308:            public boolean hasRigidSubterms() {
309:                for (int i = 0, ar = arity(); i < ar; i++) {
310:                    if (sub(i) == null) {
311:                        Debug.fail("FREE " + op + " " + i);
312:                    }
313:                    if (!sub(i).isRigid())
314:                        return false;
315:                }
316:
317:                return true;
318:            }
319:
320:            /**
321:             * retrieves if the evaluation of the term is state independant. It is
322:             * guaranteed that if the result is <code>true</code> then the value is
323:             * state independant. In case of <code>false</code> no such guarantee is 
324:             * given i.e. the terms value may be the same in all states or not.
325:             * (safe approximation)  
326:             * @return false if the value of this term may be changed by
327:             * modalities (otherwise, however, the result may also be false)
328:             */
329:            public final boolean isRigid() {
330:                return rigid;
331:            }
332:
333:            /** @return JavaBlock if term has diamond at the top level */
334:            public JavaBlock javaBlock() {
335:                return JavaBlock.EMPTY_JAVABLOCK;
336:            }
337:
338:            /** 
339:             * returns the set of metavariables that are part of this term 
340:             * (metavariables are thought as placeholder for some gound term, whereas
341:             * the variables in <code>freeVars</code> are bound by some quantifier above)
342:             * @return the set of metavariables
343:             */
344:            public SetOfMetavariable metaVars() {
345:                return metaVars;
346:            }
347:
348:            /** 
349:             * the top operator in "A and B" it is "and", in f(x,y) it is "f"
350:             * @return operator at the top
351:             */
352:            public Operator op() {
353:                return op;
354:            }
355:
356:            /**
357:             * returns the sort of the term
358:             * @return the sort of the term 
359:             */
360:            public Sort sort() {
361:                return sort;
362:            }
363:
364:            /** 
365:             * returns the <code>nr</code>-th direct subterm 
366:             * @param nr the int specifying the <tt>nr</tt>-th direct subterm 
367:             */
368:            public abstract Term sub(int nr);
369:
370:            /**
371:             * returns subterm at the position specified by the given PosInTerm pos.
372:             * @param pos the position of the wanted subterm
373:             * @return the subterm that is specified by pos
374:             */
375:            public Term subAt(PosInTerm pos) {
376:                Term sub = this ;
377:                for (final IntIterator it = pos.iterator(); it.hasNext();) {
378:                    sub = sub.sub(it.next());
379:                }
380:                return sub;
381:            }
382:
383:            /**
384:             * returns the array of variables the top level operator binds at the n-th
385:             * sub term 
386:             * @return the bound variables for the n-th subterm 
387:             */
388:            public abstract ArrayOfQuantifiableVariable varsBoundHere(int n);
389:
390:            /**
391:             * returns a linearized textual representation of this term 
392:             */
393:            public String toString() {
394:                StringBuffer sb = new StringBuffer(op().name().toString());
395:                if (arity() == 0)
396:                    return sb.toString();
397:                sb.append("(");
398:                for (int i = 0, ar = arity(); i < ar; i++) {
399:                    for (int j = 0, vbSize = varsBoundHere(i).size(); j < vbSize; j++) {
400:                        if (j == 0) {
401:                            sb.append("{");
402:                        }
403:                        sb.append(varsBoundHere(i).getQuantifiableVariable(j));
404:                        if (j != varsBoundHere(i).size() - 1) {
405:                            sb.append(", ");
406:                        } else {
407:                            sb.append("}");
408:                        }
409:                    }
410:                    sb.append(sub(i));
411:                    if (i < ar - 1) {
412:                        sb.append(",");
413:                    }
414:                }
415:                sb.append(")");
416:                return sb.toString();
417:            }
418:
419:            //  =============== For debugging, used in Main (COMPUTE_SPEC_OP-Z) =================
420:
421:            public void tree() {
422:                System.out.println("==============================");
423:                tree(this , 0);
424:            }
425:
426:            private void tree(Term t, int off) {
427:                int i;
428:                for (i = 0; i < off; i++)
429:                    System.out.print(" ");
430:                String s = t.op().toString();
431:                s = s.substring(s.lastIndexOf(".") + 1, s.length());
432:                System.out.println(t + " [" + s + "]");
433:                for (i = 0; i < t.arity(); i++)
434:                    tree(t.sub(i), off + 3);
435:            }
436:
437:        }
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