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csjavacc/struct/Lookahead.java

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+/*
+ * Copyright © 2002 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * California 95054, U.S.A. All rights reserved.  Sun Microsystems, Inc. has
+ * intellectual property rights relating to technology embodied in the product
+ * that is described in this document. In particular, and without limitation,
+ * these intellectual property rights may include one or more of the U.S.
+ * patents listed at http://www.sun.com/patents and one or more additional
+ * patents or pending patent applications in the U.S. and in other countries.
+ * U.S. Government Rights - Commercial software. Government users are subject
+ * to the Sun Microsystems, Inc. standard license agreement and applicable
+ * provisions of the FAR and its supplements.  Use is subject to license terms.
+ * Sun,  Sun Microsystems,  the Sun logo and  Java are trademarks or registered
+ * trademarks of Sun Microsystems, Inc. in the U.S. and other countries.  This
+ * product is covered and controlled by U.S. Export Control laws and may be
+ * subject to the export or import laws in other countries.  Nuclear, missile,
+ * chemical biological weapons or nuclear maritime end uses or end users,
+ * whether direct or indirect, are strictly prohibited.  Export or reexport
+ * to countries subject to U.S. embargo or to entities identified on U.S.
+ * export exclusion lists, including, but not limited to, the denied persons
+ * and specially designated nationals lists is strictly prohibited.
+ */
+
+package csjavacc.struct;
+
+
+/**
+ * Describes lookahead rule for a particular expansion or expansion
+ * sequence (See Sequence.java).  In case this describes the lookahead
+ * rule for a single expansion unit, then a sequence is created with
+ * this node as the first element, and the expansion unit as the second
+ * and last element.
+ */
+
+public class Lookahead extends Expansion {
+
+  /**
+   * Contains the list of tokens that make up the semantic lookahead
+   * if any.  If this node represents a different kind of lookahead (other
+   * than semantic lookahead), then this vector contains nothing.  If
+   * this vector contains something, then it is the boolean expression
+   * that forms the semantic lookahead.  In this case, the following
+   * fields "amount" and "la_expansion" are ignored.
+   */
+  public java.util.Vector action_tokens = new java.util.Vector();
+
+  /**
+   * The lookahead amount.  Its default value essentially gives us
+   * infinite lookahead.
+   */
+  public int amount = Integer.MAX_VALUE;
+
+  /**
+   * The expansion used to determine whether or not to choose the
+   * corresponding parse option.  This expansion is parsed upto
+   * "amount" tokens of lookahead or until a complete match for it
+   * is found.  Usually, this is the same as the expansion to be
+   * parsed.
+   */
+  public Expansion la_expansion;
+
+  /**
+   * Is set to true if this is an explicit lookahead specification.
+   */
+  public boolean isExplicit;
+
+}