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/* Copyright (c) 2006, Sun Microsystems, Inc.
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 *     * Redistributions of source code must retain the above copyright notice,
 *       this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the Sun Microsystems, Inc. nor the names of its
 *       contributors may be used to endorse or promote products derived from
 *       this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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 */

This version of the GUI parsing example defines the GUI interaction as
a JavaCC lexical specification where the characters are read from the
GUI and there is an finite automaton (FA) built out of lexical states
that have moves on these characters. In the grammar, the
USER_CHAR_STREAM option is set to true and the BUILD_PARSER option has
been set to false.  The event handler method stuffs the characters into
a buffer from which characters are returned to the lexical analyzer
(by readChar). The whole system is invoked through Main.java.

The point of this example is to illustrate:

. A very detailed example of an FA simulation using lexical states
  where every character moves the FA.

. How a lexical analyzer can be used without a standard (JavaCC
  generated) CharStream object.

. How a lexical analyzer can be used without a parser.

. The fact that input can come from entities that are not even streams
  (a GUI in this example).

. That GUI interaction can be modeled as a regular expression
  specification.

To run the calculator (which is what this example implements), do:

	javacc CalcInput.jj
	javac *.java
	java Main

Homework:

   Simplify the grammar so that (["0"-"9"])* is treated as a single
   entity for moving the FA.