Lookahead


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22  
23  package org.javacc.parser;
24  
25  /**
26   * Describes lookahead rule for a particular expansion or expansion
27   * sequence (See Sequence.java).  In case this describes the lookahead
28   * rule for a single expansion unit, then a sequence is created with
29   * this node as the first element, and the expansion unit as the second
30   * and last element.
31   */
32  
33  public class Lookahead extends Expansion {
34  
35    /**
36     * Contains the list of tokens that make up the semantic lookahead
37     * if any.  If this node represents a different kind of lookahead (other
38     * than semantic lookahead), then this vector contains nothing.  If
39     * this vector contains something, then it is the boolean expression
40     * that forms the semantic lookahead.  In this case, the following
41     * fields "amount" and "la_expansion" are ignored.
42     */
43    public java.util.Vector   action_tokens = new java.util.Vector  ();
44  
45    /**
46     * The lookahead amount.  Its default value essentially gives us
47     * infinite lookahead.
48     */
49    public int amount = Integer.MAX_VALUE;
50  
51    /**
52     * The expansion used to determine whether or not to choose the
53     * corresponding parse option.  This expansion is parsed upto
54     * "amount" tokens of lookahead or until a complete match for it
55     * is found.  Usually, this is the same as the expansion to be
56     * parsed.
57     */
58    public Expansion la_expansion;
59  
60    /**
61     * Is set to true if this is an explicit lookahead specification.
62     */
63    public boolean isExplicit;
64  
65  }
66
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