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JEP is a Java library for parsing and evaluating mathematical expressions.

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/*****************************************************************************

 JEP 2.4.1, Extensions 1.1.1
      April 30 2007
      (c) Copyright 2007, Nathan Funk and Richard Morris
      See LICENSE-*.txt for license information.

*****************************************************************************/

/*****************************************************************************

JEP - Java Math Expression Parser 2.24
	  December 30 2002
	  (c) Copyright 2002, Nathan Funk
	  See LICENSE.txt for license information.

*****************************************************************************/

/**
 * Console - JEP Example Applet
 * Copyright (c) 2000 Nathan Funk
 *
 * @author Nathan Funk , Richard Morris
 */

package org.lsmp.djepExamples;
import org.nfunk.jep.*;
import java.io.*;
import java.util.*;
import java.applet.*;
import java.awt.*;
import java.awt.event.*;

/**
* This class implements a simple command line utility for evaluating
* mathematical expressions.
* 
*   Usage: java org.lsmp.djepExamples.Console [expression]
* 
* If an argument is passed, it is interpreted as an expression * and evaluated. Otherwise, a prompt is printed, and the user can enter * expressions to be evaluated. * *

* This class has been designed to be sub classed to allow different * consol applications. * The methods *

* public void initialise()
* public void processEquation(Node node) throws Exception
* public boolean testSpecialCommands(String command)
* public void printPrompt()
* public void printIntroText()
* public void printHelp()
* 
* can all be overwritten. *

*

* Furthermore main should be overwritten. For example *

 
* 	public static void main(String args[]) {
*		Console c = new DJepConsole();
*		c.run(args);
*	}
*
*/ public class Console extends Applet implements KeyListener { private static final long serialVersionUID = 9035584745289937584L; /** Main JEP object */ protected JEP j; /** The input reader */ private BufferedReader br; /** Text area for user input in applets. */ protected TextArea ta = null; /** Constructor */ public Console() { br = new BufferedReader(new InputStreamReader(System.in)); } /** Applet initialization */ public void init() { initialise(); this.setLayout(new BorderLayout(1,1)); ta = new TextArea("",10,80,TextArea.SCROLLBARS_BOTH); ta.setEditable(true); ta.addKeyListener(this); add("Center",ta); printIntroText(); print(getPrompt()); } /** Creates a new Console object and calls run() */ public static void main(String args[]) { Console c = new Console(); c.run(args); } /** The main entry point with command line arguments */ public void run(String args[]) { initialise(); if (args.length>0) { for (int i=1; i *
  • Tests for exit, quit, and help.
  • *
  • Tests for any special commands used by sub classes. * {@link #testSpecialCommands(String)}
  • *
  • Parses the command.
  • *
  • Processes the node. {@link #processEquation(Node)}
  • *
  • Checks for errors. {@link #handleError(Exception)}
  • * * * @param command The line to be processed * @return false if un-recoverable error or 'quit' or 'exit' */ public boolean processCommand(String command) { if(command.equals("quit") || command.equals("exit")) return false; if(command.equals("help")) { printHelp(); return true; } if(command.equals("functions")) { printFuns(); return true; } if(command.equals("operators")) { printOps(); return true; } if(command.equals("variables")) { printVars(); return true; } if(!testSpecialCommands(command)) return true; try { Node n = j.parse(command); processEquation(n); } catch(Exception e) { return handleError(e); } return true; } /** sets up all the needed objects. */ public void initialise() { j = new JEP(); j.addStandardConstants(); j.addStandardFunctions(); j.addComplex(); j.setAllowUndeclared(true); j.setAllowAssignment(true); j.setImplicitMul(true); } /** Performs the required operation on a node. * Typically evaluates the node and prints the value. * * @param node Node representing expression * @throws ParseException if a Parse or evaluation error */ public void processEquation(Node node) throws ParseException { Object res = j.evaluate(node); println(res); } /** * Get a command from the input. * @return null if an IO error or EOF occurs. */ protected String getCommand() { String s=null; if (br == null) return null; try { if ( (s = br.readLine()) == null) return null; } catch(IOException e) { println("IOError exiting"); return null; } return s; } /** Prints the prompt string. */ public String getPrompt() { return "JEP > "; } /** Prints a standard help message. * Type 'quit' or 'exit' to quit, 'help' for help. **/ public final void printStdHelp() { if(ta == null) println("Type 'quit' or 'exit' to quit, 'help' for help."); else println("Type 'help' for help."); } /** Print help message. */ public void printHelp() { printStdHelp(); println("'functions' lists defined functions"); println("'operators' lists defined operators"); println("'variables' lists variables and constants"); } /** Prints introductory text. */ public void printIntroText() { println("JEP Console."); printStdHelp(); } /** Prints a list of defined functions. */ public void printFuns() { FunctionTable ft = j.getFunctionTable(); println("Known functions:"); for(Enumeration loop = ft.keys();loop.hasMoreElements();) { String s = (String) loop.nextElement(); println("\t"+s); } } /** Prints a list of defined operators. */ public void printOps() { OperatorSet opset = j.getOperatorSet(); Operator ops[] = opset.getOperators(); println("Known operators:"); for(int i=0;iverbose on
    * This method can be used detected this input, * perform required actions and skip normal processing by returning true. * * @param command * @return true indicates normal processing should continue (default) false if the command is special and no further processing should be performed (parsing and evaluating) * @see #split(String) */ public boolean testSpecialCommands(String command) { return true; } /** * Handle an error in the parse and evaluate routines. * @param e * @return false if the error cannot be recovered and the program should exit */ public boolean handleError(Exception e) { if(e instanceof ParseException) { println("Parse Error: "+e.getMessage()); } else println("Error: "+e.getClass().getName()+" "+e.getMessage()); return true; } /** Splits a string on spaces. * * @param s the input string * @return an array of the tokens in the string */ public String[] split(String s) { StringTokenizer st = new StringTokenizer(s); int tokCount = st.countTokens(); String res[] = new String[tokCount]; int pos=0; while (st.hasMoreTokens()) { res[pos++]=st.nextToken(); } return res; } /** Prints a line of text no newline. * Subclasses should call this method rather than * System.out.print to allow for output to different places. * */ public void print(Object o) { String s=null; if(o == null) s = "null"; else s = o.toString(); if(ta != null) ta.append(s); else System.out.print(s); } /** Prints a line of text no newline. * Subclasses should call this method rather than * System.out.print to allow for output to different places. */ public void println(Object o) { String s=null; if(o == null) s = "null"; else s = o.toString(); if(ta != null) ta.append(s + "\n"); else System.out.println(s); } /** * Handles keyRelease events */ public void keyReleased(KeyEvent event) { int code = event.getKeyCode(); if(code == KeyEvent.VK_ENTER) { int cpos = ta.getCaretPosition(); String alltext = ta.getText(); String before = alltext.substring(0,cpos-1); int startOfLine = before.lastIndexOf('\n'); if(startOfLine > 0) before = before.substring(startOfLine+1); String prompt = getPrompt(); String line=null; if(before.startsWith(prompt)) { line = before.substring(prompt.length()); this.processCommand(line); } // System.out.println("line ("+line+")"); //if(!flag) this.exit(); this.print(getPrompt()); } } public void keyPressed(KeyEvent arg0) { } public void keyTyped(KeyEvent arg0) { } public String getAppletInfo() { return "Jep Console applet\n" + "R Morris Mar 2005\n" + "See http://www.singsurf.org/djep/"; } }



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