calcinput.jj

经典的java语言分析器

/*
 * 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.
 */


options {
  USER_TOKEN_MANAGER = true;
}

PARSER_BEGIN(CalcInputParser)

public class CalcInputParser {
}

PARSER_END(CalcInputParser)

void Input() :
	{
	  double larg = 0.0;
	  double rarg;
	}
{
  ( 
    [
      larg=Number() 
	{
	  CalcGUI.print(larg);
	}
    ]
    (
      <ADD>
      rarg=Number()
	{
	  larg = larg + rarg;
	  CalcGUI.print(larg);
	}
    |
      <SUB>
      rarg=Number()
	{
	  larg = larg - rarg;
	  CalcGUI.print(larg);
	}
    |
      <MUL>
      rarg=Number()
	{
	  larg = larg * rarg;
	  CalcGUI.print(larg);
	}
    |
      <DIV>
      rarg=Number()
	{
	  larg = (rarg==0) ? Float.POSITIVE_INFINITY : (larg / rarg);
	  CalcGUI.print(larg);
	}
    )*
    <EQ: "=" >
  )*
}

double Number() :
	{
	  Token t;
	  String image = "";
	  double value = 0.0;
	  double decimalPlace = 1.0;
	}
{
  (
    t=<DIGIT>
	{
	  image += t.image;
	  value = value*10 + Integer.parseInt(t.image);
	  CalcGUI.print(image);
	}
  )+
  [
    <DOT>
	{
	  image += ".";
	  CalcGUI.print(image);
	}
    (
      t=<DIGIT>
	{
	  image += t.image;
	  decimalPlace *= 0.1;
	  value = value + Integer.parseInt(t.image)*decimalPlace;
	  CalcGUI.print(image);
	}
    )+
  ]
	{
	  return value;
	}
|
  <DOT>
	{
	  image = "0.";
	  CalcGUI.print(image);
	}
  (
    t=<DIGIT>
	{
	  image += t.image;
	  decimalPlace *= 0.1;
	  value = value + Integer.parseInt(t.image)*decimalPlace;
	  CalcGUI.print(image);
	}
  )+
	{
	  return value;
	}
}