javacc-7.0.4.src.main.java.org.javacc.parser.ExpansionTreeWalker Maven / Gradle / Ivy

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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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package org.javacc.parser;

import java.util.Iterator;

/**
 * A set of routines that walk down the Expansion tree in
 * various ways.
 */
public final class ExpansionTreeWalker {
  private ExpansionTreeWalker() {}

  /**
   * Visits the nodes of the tree rooted at "node" in pre-order.
   * i.e., it executes opObj.action first and then visits the
   * children.
   */
  static void preOrderWalk(Expansion node, TreeWalkerOp opObj) {
    opObj.action(node);
    if (opObj.goDeeper(node)) {
      if (node instanceof Choice) {
        for (Iterator it = ((Choice)node).getChoices().iterator(); it.hasNext();) {
          preOrderWalk((Expansion)it.next(), opObj);
        }
      } else if (node instanceof Sequence) {
        for (Iterator it = ((Sequence)node).units.iterator(); it.hasNext();) {
          preOrderWalk((Expansion)it.next(), opObj);
        }
      } else if (node instanceof OneOrMore) {
        preOrderWalk(((OneOrMore)node).expansion, opObj);
      } else if (node instanceof ZeroOrMore) {
        preOrderWalk(((ZeroOrMore)node).expansion, opObj);
      } else if (node instanceof ZeroOrOne) {
        preOrderWalk(((ZeroOrOne)node).expansion, opObj);
      } else if (node instanceof Lookahead) {
        Expansion nested_e = ((Lookahead)node).getLaExpansion();
        if (!(nested_e instanceof Sequence && (Expansion)(((Sequence)nested_e).units.get(0)) == node)) {
          preOrderWalk(nested_e, opObj);
        }
      } else if (node instanceof TryBlock) {
        preOrderWalk(((TryBlock)node).exp, opObj);
      } else if (node instanceof RChoice) {
        for (Iterator it = ((RChoice)node).getChoices().iterator(); it.hasNext();) {
          preOrderWalk((Expansion)it.next(), opObj);
        }
      } else if (node instanceof RSequence) {
        for (Iterator it = ((RSequence)node).units.iterator(); it.hasNext();) {
          preOrderWalk((Expansion)it.next(), opObj);
        }
      } else if (node instanceof ROneOrMore) {
        preOrderWalk(((ROneOrMore)node).regexpr, opObj);
      } else if (node instanceof RZeroOrMore) {
        preOrderWalk(((RZeroOrMore)node).regexpr, opObj);
      } else if (node instanceof RZeroOrOne) {
        preOrderWalk(((RZeroOrOne)node).regexpr, opObj);
      } else if (node instanceof RRepetitionRange) {
        preOrderWalk(((RRepetitionRange)node).regexpr, opObj);
      }
    }
  }

  /**
   * Visits the nodes of the tree rooted at "node" in post-order.
   * i.e., it visits the children first and then executes
   * opObj.action.
   */
  static void postOrderWalk(Expansion node, TreeWalkerOp opObj) {
    if (opObj.goDeeper(node)) {
      if (node instanceof Choice) {
        for (Iterator it = ((Choice)node).getChoices().iterator(); it.hasNext();) {
          postOrderWalk((Expansion)it.next(), opObj);
        }
      } else if (node instanceof Sequence) {
        for (Iterator it = ((Sequence)node).units.iterator(); it.hasNext();) {
          postOrderWalk((Expansion)it.next(), opObj);
        }
      } else if (node instanceof OneOrMore) {
        postOrderWalk(((OneOrMore)node).expansion, opObj);
      } else if (node instanceof ZeroOrMore) {
        postOrderWalk(((ZeroOrMore)node).expansion, opObj);
      } else if (node instanceof ZeroOrOne) {
        postOrderWalk(((ZeroOrOne)node).expansion, opObj);
      } else if (node instanceof Lookahead) {
        Expansion nested_e = ((Lookahead)node).getLaExpansion();
        if (!(nested_e instanceof Sequence && (Expansion)(((Sequence)nested_e).units.get(0)) == node)) {
          postOrderWalk(nested_e, opObj);
        }
      } else if (node instanceof TryBlock) {
        postOrderWalk(((TryBlock)node).exp, opObj);
      } else if (node instanceof RChoice) {
        for (Iterator it = ((RChoice)node).getChoices().iterator(); it.hasNext();) {
          postOrderWalk((Expansion)it.next(), opObj);
        }
      } else if (node instanceof RSequence) {
        for (Iterator it = ((RSequence)node).units.iterator(); it.hasNext();) {
          postOrderWalk((Expansion)it.next(), opObj);
        }
      } else if (node instanceof ROneOrMore) {
        postOrderWalk(((ROneOrMore)node).regexpr, opObj);
      } else if (node instanceof RZeroOrMore) {
        postOrderWalk(((RZeroOrMore)node).regexpr, opObj);
      } else if (node instanceof RZeroOrOne) {
        postOrderWalk(((RZeroOrOne)node).regexpr, opObj);
      } else if (node instanceof RRepetitionRange) {
        postOrderWalk(((RRepetitionRange)node).regexpr, opObj);
      }
    }
    opObj.action(node);
  }

}