Console


1   /*****************************************************************************
2   
3   JEP - Java Math Expression Parser 2.3.0
4         October 3 2004
5         (c) Copyright 2004, Nathan Funk and Richard Morris
6         See LICENSE.txt for license information.
7   
8   *****************************************************************************/
9   
10  /**
11   * Console - JEP Example Applet
12   * Copyright (c) 2000 Nathan Funk
13   *
14   * @author Nathan Funk 
15   */
16  
17  package org.nfunk.jepexamples;
18  
19  import java.io.*;
20  import org.nfunk.jep.JEP;
21  //import org.nfunk.sovler.*;
22  
23  /**
24  * This class implements a simple command line utility for evaluating
25  * mathematical expressions.
26  *
27  *   Usage: java org.nfunk.jepexamples.Console [expression]
28  *
29  * If an argument is passed, it is interpreted as an expression
30  * and evaluated. Otherwise, a prompt is printed, and the user can enter
31  * expressions to be evaluated. To exit from the command prompt a 'q' must
32  * be entered.
33  */
34  class Console {
35      
36      /** The prompt string */
37      private String   prompt;
38      
39      /** The input reader */
40      private BufferedReader br;
41      
42      /** Constructor */
43      public Console() {
44          prompt = "JEP > ";
45          br = new BufferedReader(new InputStreamReader(System.in));
46  
47      }
48  
49      /** Creates a new Console object and calls run() */
50      public static void main(String   args[]) throws IOException {
51          Console c = new Console();
52          c.run(args);
53      }
54      
55      /** The input loop */
56      public void run(String   args[]) throws IOException {
57          String   command="";
58          JEP j = new JEP();
59          j.addStandardConstants();
60          j.addStandardFunctions();
61          j.addComplex();
62          //j.setTraverse(true);
63  
64          if (args.length>0) {
65              // evaluate the expression passed as arguments
66              String   temp = args[0];
67              for (int i=1; i<args.length; i++) temp += " " + args[i];
68              j.parseExpression(temp);
69              if (j.hasError())
70                  System.out.println(j.getErrorInfo());
71              else
72                  System.out.println(j.getValueAsObject());
73          } else {
74              // no arguments - interactive mode
75                  
76              System.out.println("JEP - Enter q to quit");    
77              System.out.print(prompt);
78  
79              while ((command = getCommand()) != null) {
80                  j.parseExpression(command);
81                  
82                  if (j.hasError()) {
83                      System.out.println(j.getErrorInfo());
84                  } else {
85                      // expression is OK, get the value
86                      Object   value = j.getValueAsObject();
87                      
88                      // did error occur during evaluation?
89                      if (j.hasError()) {
90                          System.out.println(j.getErrorInfo());
91                      } else {
92                          System.out.println(value);
93                      }
94  
95  /*
96                      System.out.println(
97                          (LinearVisitor.isLinear(j.getTopNode())) ?
98                          "Linear" : "Not Linear");
99                      System.out.println(
100                         (ConstantVisitor.isConstant(j.getTopNode())) ?
101                         "Constant" : "Not Constant");
102 */
103                 }
104                     
105                 System.out.print(prompt);
106             }
107         }
108         
109     }
110     
111     /**
112      * Get a command from the input.
113      * @return null if an error occures, or if the user enters a terminating
114      *  command
115      */
116     private String   getCommand() throws IOException {
117         String   s;
118         
119         if (br == null)
120             return null;
121 
122         if ( (s = br.readLine()) == null)
123             return null;
124 
125         if (s.equals("q")
126             || s.equals("quit")
127             || s.equals("exit"))
128             return null;
129         
130         return s;
131     }
132 }
133
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