function.java

JAVA 数学程序库 提供常规的数值计算程序包

package jmathlib.core.functions;

import jmathlib.core.interpreter.*;
import jmathlib.core.tokens.OperandToken;
import jmathlib.core.tokens.FunctionToken;
import jmathlib.core.tokens.Token;

/**This is the base class for all functions*/
abstract public class Function extends RootObject
{
	/**The functions name*/
	protected String name;

    /** path and filename where this function is located on the disc*/
    protected String pathAndFileName;
    
    /** data and time of last modification of this file on disc*/
    protected long lastModified;

    /**Number of left-hand arguments (e.g. [a,b,c]=some_functions() ) */
	private int nargout = 0;

	/**Default constructor - Creates a function with a null name*/
	public Function()
	{
		name = "";
	}

	/**Creates a function called _name
	@param _name = the name of the function*/
	public Function(String _name)
	{
		name = _name;
	}

    /**@return the name of the function*/
    public String getName()
    {
        return name;
    }


    /**
     * sets the path and filename that belongs to this functions 
     * @param _pathAndFileName
     */
    public void setPathAndFileName(String _pathAndFileName)
    {
        pathAndFileName = _pathAndFileName;
    }  

    /**
     * returns the path and filename that belongs to this functions 
     * @return path and filename
     */ 
    public String getPathAndFileName()
    {
        return pathAndFileName;
    }

    /**
     * Set the date of last modification of this function
     * @param _lastModified
     */
    public void setLastModified(long _lastModified)
    {
        lastModified = _lastModified;
    }  

    /**
     * Returns the date of last modification of this function
     * @return date of last modification
     */
    public long getLastModified()
    {
        return lastModified;
    }

    /**Sets the name of this function
    @param name = name of this function */
	public void setName(String _name)
	{
	    name = _name;
	}  
 
	/**Returns the number of left-hand arguments of the function 
	 (e.g.) [a,b,c]=some_function will return "3"              
	 @return the number of left hand arguments*/
	public int getNoOfLeftHandArguments()
	{
		return nargout;
	}

	/**Returns the number of left-hand arguments of the function 
	 (e.g.) [a,b,c]=some_function will return "3"              
	 @return the number of left hand arguments*/
	protected int getNArgOut()
	{
		return nargout;
	}

	/**Returns the number of right-hand arguments of the function
      (e.g.: a=some_function(a,b,c,d) will return "4"
      @return number of right hand arguments. Returns -1 if there
              are no right hand arguments. Returns also -1 if there
              if one argument==null  */
	protected int getNArgIn(Token[] operands)
	{
		// Check if there are arguments at all
		if (operands == null)
			return -1;

		return  operands.length;
	}

	/**Sets the number of left-hand arguments of the function    
	 (e.g.) [a,b,c]=some_function will return set a "3"        
	@param _number = the number of left hand arguments*/
	public void setNoOfLeftHandArguments(int _number)
	{
		nargout = _number;
	}


	/**Tests if an object is equal to this function
		if obj is an instance of Function or Function token then it
		compares the name of obj to the functions name otherwise it
		calls the superclasses version
		@param obj = object to test
		@return true if the objects are equal*/
	public boolean equals(Object obj)
	{
		boolean equal = false;
		if(obj instanceof Function)
			equal = ((Function)obj).getName().toUpperCase() == name.toUpperCase();
		else if(obj instanceof FunctionToken)
			equal = ((FunctionToken)obj).getName().toUpperCase() == name.toUpperCase();
		else
			equal = super.equals(obj);
		return equal;
	}

	/**Executes the function
		@param operands - an array of the functions paramaters
		@return the result as an OperandToken*/
	abstract public OperandToken evaluate(Token[] operands);

    /**Throws arithmetic exception for external functions
     * @param error text to display
     * */
    public void throwMathLibException(String errorMessage)
    {
        Errors.throwMathLibException(errorMessage);
    }
    
    /** write debug line to std-out and file
     * 
     * @param s
     */
    public void debugLine(String s)
    {
        ErrorLogger.debugLine(s);
    }
    
}