1 // Copyright 2003 Adam Megacz, see the COPYING file for licensing [GPL]
8 * Parses a stream of lexed tokens into a tree of Function's.
10 * There are three kinds of things we parse: blocks, statements, and
13 * - Expressions are a special type of statement that evaluates to a
14 * value (for example, "break" is not an expression, * but "3+2"
15 * is). Some tokens sequences start expressions (for * example,
16 * literal numbers) and others continue an expression which * has
17 * already been begun (for example, '+'). Finally, some *
18 * expressions are valid targets for an assignment operation; after
19 * * each of these expressions, continueExprAfterAssignable() is
20 * called * to check for an assignment operation.
22 * - A statement ends with a semicolon and does not return a value.
24 * - A block is a single statement or a sequence of statements
25 * surrounded by curly braces.
27 * Each parsing method saves the parserLine before doing its actual
28 * work and restores it afterwards. This ensures that parsing a
29 * subexpression does not modify the line number until a token
30 * *after* the subexpression has been consumed by the parent
33 * Technically it would be a better design for this class to build an
34 * intermediate parse tree and use that to emit bytecode. Here's the
37 * Advantages of building a parse tree:
38 * - easier to apply optimizations
39 * - would let us handle more sophisticated languages than JavaScript
41 * Advantages of leaving out the parse tree
42 * - faster compilation
43 * - less load on the garbage collector
44 * - much simpler code, easier to understand
47 * Fortunately JS is such a simple language that we can get away with
48 * the half-assed approach and still produce a working, complete
51 * The bytecode language emitted doesn't really cause any appreciable
52 * semantic loss, and is itself a parseable language very similar to
53 * Forth or a postfix variant of LISP. This means that the bytecode
54 * can be transformed into a parse tree, which can be manipulated.
55 * So if we ever want to add an optimizer, it could easily be done by
56 * producing a parse tree from the bytecode, optimizing that tree,
57 * and then re-emitting the bytecode. The parse tree node class
58 * would also be much simpler since the bytecode language has so few
61 * Actually, the above paragraph is slightly inaccurate -- there are
62 * places where we push a value and then perform an arbitrary number
63 * of operations using it before popping it; this doesn't parse well.
64 * But these cases are clearly marked and easy to change if we do
65 * need to move to a parse tree format.
67 class Parser extends Lexer implements ByteCodes {
70 // Constructors //////////////////////////////////////////////////////
72 public Parser(Reader r, String sourceName, int line) throws IOException { super(r, sourceName, line); }
75 public static void main(String[] s) throws Exception {
76 Function block = new Function("stdin", 0, new InputStreamReader(System.in), null);
77 if (block == null) return;
78 System.out.println(block);
82 // Statics ////////////////////////////////////////////////////////////
84 static byte[] precedence = new byte[MAX_TOKEN + 1];
85 static boolean[] isRightAssociative = new boolean[MAX_TOKEN + 1];
86 // Use this as the precedence when we want anything up to the comma
87 private final static int NO_COMMA = 2;
89 isRightAssociative[ASSIGN] =
90 isRightAssociative[ASSIGN_BITOR] =
91 isRightAssociative[ASSIGN_BITXOR] =
92 isRightAssociative[ASSIGN_BITAND] =
93 isRightAssociative[ASSIGN_LSH] =
94 isRightAssociative[ASSIGN_RSH] =
95 isRightAssociative[ASSIGN_URSH] =
96 isRightAssociative[ASSIGN_ADD] =
97 isRightAssociative[ASSIGN_SUB] =
98 isRightAssociative[ASSIGN_MUL] =
99 isRightAssociative[ASSIGN_DIV] =
100 isRightAssociative[ASSIGN_MOD] = true;
102 precedence[COMMA] = 1;
103 // 2 is intentionally left unassigned. we use minPrecedence==2 for comma separated lists
105 precedence[ASSIGN_BITOR] =
106 precedence[ASSIGN_BITXOR] =
107 precedence[ASSIGN_BITAND] =
108 precedence[ASSIGN_LSH] =
109 precedence[ASSIGN_RSH] =
110 precedence[ASSIGN_URSH] =
111 precedence[ASSIGN_ADD] =
112 precedence[ASSIGN_SUB] =
113 precedence[ASSIGN_MUL] =
114 precedence[ASSIGN_DIV] =
115 precedence[ASSIGN_MOD] = 3;
116 precedence[HOOK] = 4;
119 precedence[BITOR] = 7;
120 precedence[BITXOR] = 8;
121 precedence[BITAND] = 9;
122 precedence[EQ] = precedence[NE] = precedence[SHEQ] = precedence[SHNE] = 10;
123 precedence[LT] = precedence[LE] = precedence[GT] = precedence[GE] = 11;
124 precedence[LSH] = precedence[RSH] = precedence[URSH] = 12;
125 precedence[ADD] = precedence[SUB] = 12;
126 precedence[MUL] = precedence[DIV] = precedence[MOD] = 13;
127 precedence[BITNOT] = precedence[BANG] = precedence[TYPEOF] = 14;
128 precedence[DOT] = precedence[LB] = precedence[LP] = precedence[INC] = precedence[DEC] = 15;
132 // Parsing Logic /////////////////////////////////////////////////////////
134 /** gets a token and throws an exception if it is not <tt>code</tt> */
135 private void consume(int code) throws IOException {
136 if (getToken() != code) throw pe("expected " + codeToString[code] + ", got " + (op == -1 ? "EOF" : codeToString[op]));
140 * Parse the largest possible expression containing no operators
141 * of precedence below <tt>minPrecedence</tt> and append the
142 * bytecodes for that expression to <tt>appendTo</tt>; the
143 * appended bytecodes MUST grow the stack by exactly one element.
145 private void startExpr(Function appendTo, int minPrecedence) throws IOException {
146 int saveParserLine = parserLine;
147 _startExpr(appendTo, minPrecedence);
148 parserLine = saveParserLine;
150 private void _startExpr(Function appendTo, int minPrecedence) throws IOException {
151 int tok = getToken();
152 Function b = appendTo;
155 case -1: throw pe("expected expression");
157 // all of these simply push values onto the stack
158 case NUMBER: b.add(parserLine, LITERAL, number); break;
159 case STRING: b.add(parserLine, LITERAL, string); break;
160 case THIS: b.add(parserLine, TOPSCOPE, null); break;
161 case NULL: b.add(parserLine, LITERAL, null); break;
162 case TRUE: case FALSE: b.add(parserLine, LITERAL, new Boolean(tok == TRUE)); break;
165 b.add(parserLine, ARRAY, new Integer(0)); // push an array onto the stack
168 if (peekToken() != RB)
169 while(true) { // iterate over the initialization values
171 b.add(parserLine, LITERAL, new Integer(i++)); // push the index in the array to place it into
172 if (peekToken() == COMMA || peekToken() == RB)
173 b.add(parserLine, LITERAL, null); // for stuff like [1,,2,]
175 startExpr(b, NO_COMMA); // push the value onto the stack
176 b.add(parserLine, PUT); // put it into the array
177 b.add(parserLine, POP); // discard the value remaining on the stack
178 if (peekToken() == RB) break;
181 b.set(size0 - 1, new Integer(i)); // back at the ARRAY instruction, write the size of the array
185 case SUB: { // negative literal (like "3 * -1")
187 b.add(parserLine, LITERAL, new Double(number.doubleValue() * -1));
190 case LP: { // grouping (not calling)
195 case INC: case DEC: { // prefix (not postfix)
196 startExpr(b, precedence[tok]);
197 int prev = b.size - 1;
198 if (b.get(prev) == GET && b.getArg(prev) != null)
199 b.set(prev, LITERAL, b.getArg(prev));
200 else if(b.get(prev) == GET)
203 throw pe("prefixed increment/decrement can only be performed on a valid assignment target");
204 b.add(parserLine, tok, Boolean.TRUE);
207 case BANG: case BITNOT: case TYPEOF: {
208 startExpr(b, precedence[tok]);
209 b.add(parserLine, tok);
212 case LC: { // object constructor
213 b.add(parserLine, OBJECT, null); // put an object on the stack
214 if (peekToken() != RC)
216 if (peekToken() != NAME && peekToken() != STRING)
217 throw pe("expected NAME or STRING");
219 b.add(parserLine, LITERAL, string); // grab the key
221 startExpr(b, NO_COMMA); // grab the value
222 b.add(parserLine, PUT); // put the value into the object
223 b.add(parserLine, POP); // discard the remaining value
224 if (peekToken() == RC) break;
226 if (peekToken() == RC) break; // we permit {,,} -- I'm not sure if ECMA does
232 b.add(parserLine, TOPSCOPE);
233 b.add(parserLine, LITERAL, string);
234 continueExprAfterAssignable(b,minPrecedence);
240 Function b2 = new Function(sourceName, parserLine, null, null);
241 b.add(parserLine, NEWFUNCTION, b2);
243 // function prelude; arguments array is already on the stack
244 b2.add(parserLine, TOPSCOPE);
245 b2.add(parserLine, SWAP);
246 b2.add(parserLine, DECLARE, "arguments"); // declare arguments (equivalent to 'var arguments;')
247 b2.add(parserLine, SWAP); // set this.arguments and leave the value on the stack
248 b2.add(parserLine, PUT);
250 while(peekToken() != RP) { // run through the list of argument names
252 if (peekToken() == NAME) {
253 consume(NAME); // a named argument
254 String varName = string;
256 b2.add(parserLine, DUP); // dup the args array
257 b2.add(parserLine, GET, new Integer(numArgs - 1)); // retrieve it from the arguments array
258 b2.add(parserLine, TOPSCOPE);
259 b2.add(parserLine, SWAP);
260 b2.add(parserLine, DECLARE, varName); // declare the name
261 b2.add(parserLine, SWAP);
262 b2.add(parserLine, PUT);
263 b2.add(parserLine, POP); // pop the value
264 b2.add(parserLine, POP); // pop the scope
266 if (peekToken() == RP) break;
271 b2.numFormalArgs = numArgs;
272 b2.add(parserLine, POP); // pop off the arguments array
273 b2.add(parserLine, POP); // pop off TOPSCOPE
275 if(peekToken() != LC)
276 throw pe("Functions must have a block surrounded by curly brackets");
278 parseBlock(b2, null); // the function body
280 b2.add(parserLine, LITERAL, null); // in case we "fall out the bottom", return NULL
281 b2.add(parserLine, RETURN);
285 default: throw pe("expected expression, found " + codeToString[tok] + ", which cannot start an expression");
288 // attempt to continue the expression
289 continueExpr(b, minPrecedence);
294 * Assuming that a complete assignable (lvalue) has just been
295 * parsed and the object and key are on the stack,
296 * <tt>continueExprAfterAssignable</tt> will attempt to parse an
297 * expression that modifies the assignable. This method always
298 * decreases the stack depth by exactly one element.
300 private void continueExprAfterAssignable(Function b,int minPrecedence) throws IOException {
301 int saveParserLine = parserLine;
302 _continueExprAfterAssignable(b,minPrecedence);
303 parserLine = saveParserLine;
305 private void _continueExprAfterAssignable(Function b,int minPrecedence) throws IOException {
306 if (b == null) throw new Error("got null b; this should never happen");
307 int tok = getToken();
308 if (minPrecedence != -1 && (precedence[tok] < minPrecedence || (precedence[tok] == minPrecedence && !isRightAssociative[tok])))
309 // force the default case
312 case ASSIGN_BITOR: case ASSIGN_BITXOR: case ASSIGN_BITAND: case ASSIGN_LSH: case ASSIGN_RSH: case ASSIGN_URSH:
313 case ASSIGN_MUL: case ASSIGN_DIV: case ASSIGN_MOD: case ASSIGN_ADD: case ASSIGN_SUB: {
314 b.add(parserLine, GET_PRESERVE);
315 startExpr(b, precedence[tok]);
317 if (tok == ASSIGN_ADD || tok == ASSIGN_SUB) {
318 b.add(parserLine, tok);
320 // tok-1 is always s/^ASSIGN_// (0 is BITOR, 1 is ASSIGN_BITOR, etc)
321 b.add(parserLine, tok - 1, tok-1==ADD ? new Integer(2) : null);
322 b.add(parserLine, PUT);
323 b.add(parserLine, SWAP);
324 b.add(parserLine, POP);
325 if (tok == ASSIGN_ADD || tok == ASSIGN_SUB) b.set(size, tok, new Integer(b.size - size));
328 case INC: case DEC: { // postfix
329 b.add(parserLine, tok, Boolean.FALSE);
333 startExpr(b, precedence[tok]);
334 b.add(parserLine, PUT);
335 b.add(parserLine, SWAP);
336 b.add(parserLine, POP);
340 int n = parseArgs(b);
342 // if the object supports GETCALL, we use this, and jump over the following two instructions
343 b.add(parserLine,CALLMETHOD,new Integer(n));
344 b.add(parserLine,GET);
345 b.add(parserLine,CALL_REVERSED,new Integer(n));
350 if(b.get(b.size-1) == LITERAL && b.getArg(b.size-1) != null)
351 b.set(b.size-1,GET,b.getArg(b.size-1));
353 b.add(parserLine, GET);
361 * Assuming that a complete expression has just been parsed,
362 * <tt>continueExpr</tt> will attempt to extend this expression by
363 * parsing additional tokens and appending additional bytecodes.
365 * No operators with precedence less than <tt>minPrecedence</tt>
368 * If any bytecodes are appended, they will not alter the stack
371 private void continueExpr(Function b, int minPrecedence) throws IOException {
372 int saveParserLine = parserLine;
373 _continueExpr(b, minPrecedence);
374 parserLine = saveParserLine;
376 private void _continueExpr(Function b, int minPrecedence) throws IOException {
377 if (b == null) throw new Error("got null b; this should never happen");
378 int tok = getToken();
379 if (tok == -1) return;
380 if (minPrecedence != -1 && (precedence[tok] < minPrecedence || (precedence[tok] == minPrecedence && !isRightAssociative[tok]))) {
386 case LP: { // invocation (not grouping)
387 int n = parseArgs(b);
388 b.add(parserLine, CALL, new Integer(n));
391 case BITOR: case BITXOR: case BITAND: case SHEQ: case SHNE: case LSH:
392 case RSH: case URSH: case MUL: case DIV: case MOD:
393 case GT: case GE: case EQ: case NE: case LT: case LE: case SUB: {
394 startExpr(b, precedence[tok]);
395 b.add(parserLine, tok);
402 startExpr(b,precedence[tok]);
404 nextTok = getToken();
405 } while(nextTok == tok);
407 b.add(parserLine, tok, new Integer(count));
411 b.add(parserLine, tok == AND ? b.JF : b.JT, new Integer(0)); // test to see if we can short-circuit
413 startExpr(b, precedence[tok]); // otherwise check the second value
414 b.add(parserLine, JMP, new Integer(2)); // leave the second value on the stack and jump to the end
415 b.add(parserLine, LITERAL, tok == AND ?
416 new Boolean(false) : new Boolean(true)); // target of the short-circuit jump is here
417 b.set(size - 1, new Integer(b.size - size)); // write the target of the short-circuit jump
421 // support foo..bar syntax for foo[""].bar
422 if (peekToken() == DOT) {
427 b.add(parserLine, LITERAL, string);
428 continueExprAfterAssignable(b,minPrecedence);
431 case LB: { // subscripting (not array constructor)
434 continueExprAfterAssignable(b,minPrecedence);
438 b.add(parserLine, JF, new Integer(0)); // jump to the if-false expression
440 startExpr(b, minPrecedence); // write the if-true expression
441 b.add(parserLine, JMP, new Integer(0)); // if true, jump *over* the if-false expression
442 b.set(size - 1, new Integer(b.size - size + 1)); // now we know where the target of the jump is
445 startExpr(b, minPrecedence); // write the if-false expression
446 b.set(size - 1, new Integer(b.size - size + 1)); // this is the end; jump to here
450 // pop the result of the previous expression, it is ignored
451 b.add(parserLine,POP);
461 continueExpr(b, minPrecedence); // try to continue the expression
464 // parse a set of comma separated function arguments, assume LP has already been consumed
465 private int parseArgs(Function b) throws IOException {
467 while(peekToken() != RP) {
469 if (peekToken() != COMMA) {
470 startExpr(b, NO_COMMA);
471 if (peekToken() == RP) break;
479 /** Parse a block of statements which must be surrounded by LC..RC. */
480 void parseBlock(Function b) throws IOException { parseBlock(b, null); }
481 void parseBlock(Function b, String label) throws IOException {
482 int saveParserLine = parserLine;
483 _parseBlock(b, label);
484 parserLine = saveParserLine;
486 void _parseBlock(Function b, String label) throws IOException {
487 if (peekToken() == -1) return;
488 else if (peekToken() != LC) parseStatement(b, null);
491 while(peekToken() != RC && peekToken() != -1) parseStatement(b, null);
496 /** Parse a single statement, consuming the RC or SEMI which terminates it. */
497 void parseStatement(Function b, String label) throws IOException {
498 int saveParserLine = parserLine;
499 _parseStatement(b, label);
500 parserLine = saveParserLine;
502 void _parseStatement(Function b, String label) throws IOException {
503 int tok = peekToken();
504 if (tok == -1) return;
505 switch(tok = getToken()) {
507 case THROW: case ASSERT: case RETURN: {
508 if (tok == RETURN && peekToken() == SEMI)
509 b.add(parserLine, LITERAL, null);
512 b.add(parserLine, tok);
516 case BREAK: case CONTINUE: {
517 if (peekToken() == NAME) consume(NAME);
518 b.add(parserLine, tok, string);
523 b.add(parserLine, TOPSCOPE); // push the current scope
526 b.add(parserLine, DECLARE, string); // declare it
527 if (peekToken() == ASSIGN) { // if there is an '=' after the variable name
529 startExpr(b, NO_COMMA);
530 b.add(parserLine, PUT); // assign it
531 b.add(parserLine, POP); // clean the stack
533 b.add(parserLine, POP); // pop the string pushed by declare
535 if (peekToken() != COMMA) break;
538 b.add(parserLine, POP); // pop off the topscope
539 if ((mostRecentlyReadToken != RC || peekToken() == SEMI) && peekToken() != -1 && mostRecentlyReadToken != SEMI) consume(SEMI);
547 b.add(parserLine, JF, new Integer(0)); // if false, jump to the else-block
549 parseStatement(b, null);
551 if (peekToken() == ELSE) {
553 b.add(parserLine, JMP, new Integer(0)); // if we took the true-block, jump over the else-block
554 b.set(size - 1, new Integer(b.size - size + 1));
556 parseStatement(b, null);
558 b.set(size - 1, new Integer(b.size - size + 1)); // regardless of which branch we took, b[size] needs to point here
563 if (label != null) b.add(parserLine, LABEL, label);
564 b.add(parserLine, LOOP);
566 b.add(parserLine, POP); // discard the first-iteration indicator
568 b.add(parserLine, JT, new Integer(2)); // if the while() clause is true, jump over the BREAK
569 b.add(parserLine, BREAK);
571 parseStatement(b, null);
572 b.add(parserLine, CONTINUE); // if we fall out of the end, definately continue
573 b.set(size - 1, new Integer(b.size - size + 1)); // end of the loop
578 if (label != null) b.add(parserLine, LABEL, label);
579 b.add(parserLine, LOOP);
585 if (peekToken() == CASE) { // we compile CASE statements like a bunch of if..else's
587 b.add(parserLine, DUP); // duplicate the switch() value; we'll consume one copy
590 b.add(parserLine, EQ); // check if we should do this case-block
591 b.add(parserLine, JF, new Integer(0)); // if not, jump to the next one
593 while(peekToken() != CASE && peekToken() != DEFAULT && peekToken() != RC) parseStatement(b, null);
594 b.set(size - 1, new Integer(1 + b.size - size));
595 } else if (peekToken() == DEFAULT) {
598 while(peekToken() != CASE && peekToken() != DEFAULT && peekToken() != RC) parseStatement(b, null);
599 } else if (peekToken() == RC) {
601 b.add(parserLine, BREAK); // break out of the loop if we 'fall through'
604 throw pe("expected CASE, DEFAULT, or RC; got " + codeToString[peekToken()]);
606 b.set(size0 - 1, new Integer(b.size - size0 + 1)); // end of the loop
611 if (label != null) b.add(parserLine, LABEL, label);
612 b.add(parserLine, LOOP);
614 parseStatement(b, null);
618 b.add(parserLine, JT, new Integer(2)); // check the while() clause; jump over the BREAK if true
619 b.add(parserLine, BREAK);
620 b.add(parserLine, CONTINUE);
623 b.set(size - 1, new Integer(b.size - size + 1)); // end of the loop; write this location to the LOOP instruction
628 b.add(parserLine, TRY); // try bytecode causes a TryMarker to be pushed
629 int tryInsn = b.size - 1;
630 // parse the expression to be TRYed
631 parseStatement(b, null);
632 // pop the try marker. this is pushed when the TRY bytecode is executed
633 b.add(parserLine, POP);
634 // jump forward to the end of the catch block, start of the finally block
635 b.add(parserLine, JMP);
636 int successJMPInsn = b.size - 1;
638 if (peekToken() != CATCH && peekToken() != FINALLY)
639 throw pe("try without catch or finally");
641 int catchJMPDistance = -1;
642 if (peekToken() == CATCH) {
643 catchJMPDistance = b.size - tryInsn;
648 exceptionVar = string;
650 b.add(parserLine, TOPSCOPE); // the exception is on top of the stack; put it to the chosen name
651 b.add(parserLine, SWAP);
652 b.add(parserLine, LITERAL,exceptionVar);
653 b.add(parserLine, SWAP);
654 b.add(parserLine, PUT);
655 b.add(parserLine, POP);
656 b.add(parserLine, POP);
657 parseStatement(b, null);
658 // pop the try and catch markers
659 b.add(parserLine,POP);
660 b.add(parserLine,POP);
663 // jump here if no exception was thrown
664 b.set(successJMPInsn, new Integer(b.size - successJMPInsn));
666 int finallyJMPDistance = -1;
667 if (peekToken() == FINALLY) {
668 b.add(parserLine, LITERAL, null); // null FinallyData
669 finallyJMPDistance = b.size - tryInsn;
671 parseStatement(b, null);
672 b.add(parserLine,FINALLY_DONE);
675 // setup the TRY arguments
676 b.set(tryInsn, new int[] { catchJMPDistance, finallyJMPDistance });
685 boolean hadVar = false; // if it's a for..in, we ignore the VAR
686 if (tok == VAR) { hadVar = true; tok = getToken(); }
687 String varName = string;
688 boolean forIn = peekToken() == IN; // determine if this is a for..in loop or not
689 pushBackToken(tok, varName);
692 b.add(parserLine, NEWSCOPE); // for-loops always create new scopes
693 b.add(parserLine, LITERAL, varName); // declare the new variable
694 b.add(parserLine, DECLARE);
696 b.add(parserLine, LOOP); // we actually only add this to ensure that BREAK works
697 b.add(parserLine, POP); // discard the first-iteration indicator
702 b.add(parserLine, PUSHKEYS); // push the keys as an array; check the length
703 b.add(parserLine, LITERAL, "length");
704 b.add(parserLine, GET);
707 b.add(parserLine, LITERAL, new Integer(1)); // decrement the length
708 b.add(parserLine, SUB);
709 b.add(parserLine, DUP);
710 b.add(parserLine, LITERAL, new Integer(0)); // see if we've exhausted all the elements
711 b.add(parserLine, LT);
712 b.add(parserLine, JF, new Integer(2));
713 b.add(parserLine, BREAK); // if we have, then BREAK
714 b.add(parserLine, GET_PRESERVE); // get the key out of the keys array
715 b.add(parserLine, LITERAL, varName);
716 b.add(parserLine, PUT); // write it to this[varName]
717 parseStatement(b, null); // do some stuff
718 b.add(parserLine, CONTINUE); // continue if we fall out the bottom
720 b.set(size - 1, new Integer(b.size - size + 1)); // BREAK to here
721 b.add(parserLine, OLDSCOPE); // restore the scope
724 if (hadVar) pushBackToken(VAR, null); // yeah, this actually matters
725 b.add(parserLine, NEWSCOPE); // grab a fresh scope
727 parseStatement(b, null); // initializer
728 Function e2 = // we need to put the incrementor before the test
729 new Function(sourceName, parserLine, null, null); // so we save the test here
730 if (peekToken() != SEMI)
733 e2.add(parserLine, b.LITERAL, Boolean.TRUE); // handle the for(foo;;foo) case
735 if (label != null) b.add(parserLine, LABEL, label);
736 b.add(parserLine, LOOP);
739 b.add(parserLine, JT, new Integer(0)); // if we're on the first iteration, jump over the incrementor
741 if (peekToken() != RP) { // do the increment thing
743 b.add(parserLine, POP);
745 b.set(size - 1, new Integer(b.size - size + 1));
748 b.paste(e2); // ok, *now* test if we're done yet
749 b.add(parserLine, JT, new Integer(2)); // break out if we don't meet the test
750 b.add(parserLine, BREAK);
751 parseStatement(b, null);
752 b.add(parserLine, CONTINUE); // if we fall out the bottom, CONTINUE
753 b.set(size2 - 1, new Integer(b.size - size2 + 1)); // end of the loop
755 b.add(parserLine, OLDSCOPE); // get our scope back
760 case NAME: { // either a label or an identifier; this is the one place we're not LL(1)
761 String possiblyTheLabel = string;
762 if (peekToken() == COLON) { // label
764 parseStatement(b, possiblyTheLabel);
766 } else { // expression
767 pushBackToken(NAME, possiblyTheLabel);
769 b.add(parserLine, POP);
770 if ((mostRecentlyReadToken != RC || peekToken() == SEMI) && peekToken() != -1 && mostRecentlyReadToken != SEMI) consume(SEMI);
775 case SEMI: return; // yep, the null statement is valid
777 case LC: { // blocks are statements too
779 b.add(parserLine, NEWSCOPE);
780 parseBlock(b, label);
781 b.add(parserLine, OLDSCOPE);
785 default: { // hope that it's an expression
788 b.add(parserLine, POP);
789 if ((mostRecentlyReadToken != RC || peekToken() == SEMI) && peekToken() != -1 && mostRecentlyReadToken != SEMI) consume(SEMI);
796 // ParserException //////////////////////////////////////////////////////////////////////
797 private IOException pe(String s) { return new IOException(sourceName + ":" + parserLine + " " + s); }