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Uniform handling of non-greedy decisions in ATN factory

This commit is contained in:
Sam Harwell 2012-10-14 12:16:33 -05:00
parent 39c73302f6
commit 9ea072aee0
1 changed files with 15 additions and 6 deletions
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21
tool/src/org/antlr/v4/automata/ParserATNFactory.java
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@ -422,9 +422,18 @@ public class ParserATNFactory implements ATNFactory {
@NotNull
@Override
public Handle optional(@NotNull GrammarAST optAST, @NotNull Handle blk) {
// TODO: no such thing as nongreedy ()? so give error
BlockStartState blkStart = (BlockStartState)blk.left;
epsilon(blkStart, blk.right);
BlockAST blkAST = (BlockAST)optAST.getChild(0);
if (isGreedy(blkAST)) {
epsilon(blkStart, blk.right);
}
else {
Transition existing = blkStart.removeTransition(0);
epsilon(blkStart, blk.right);
blkStart.addTransition(existing);
}
optAST.atnState = blk.left;
return blk;
}
@ -454,11 +463,11 @@ public class ParserATNFactory implements ATNFactory {
epsilon(blkEnd, loop); // blk can see loop back
BlockAST blkAST = (BlockAST)plusAST.getChild(0);
if ( !g.isLexer() || isGreedy(blkAST) ) {
if ( isGreedy(blkAST) ) {
epsilon(loop, blkStart); // loop back to start
epsilon(loop, end); // or exit
}
else { // only lexers flip entry/exit branches for nongreedy
else {
// if not greedy, priority to exit branch; make it first
epsilon(loop, end); // exit
epsilon(loop, blkStart); // loop back to start
@ -493,11 +502,11 @@ public class ParserATNFactory implements ATNFactory {
end.loopBackState = loop;
BlockAST blkAST = (BlockAST)starAST.getChild(0);
if ( !g.isLexer() || isGreedy(blkAST) ) {
if ( isGreedy(blkAST) ) {
epsilon(entry, blkStart); // loop enter edge (alt 1)
epsilon(entry, end); // bypass loop edge (alt 2)
}
else { // only lexers flip entry/exit branches for nongreedy
else {
// if not greedy, priority to exit branch; make it first
epsilon(entry, end); // bypass loop edge (alt 1)
epsilon(entry, blkStart); // loop enter edge (alt 2)