package gve.calc.formula;

import java.util.Vector;
import java.util.Hashtable;

 @version 4 nov 1999
  @author Geert Vernaeve
  This evaluator is able to undo multiple redefinitions of the same variable.
 
public class MultiEvaluator implements Evaluator
{
	private Vector identifiers,values;
	private Hashtable functions = new Hashtable();

	public MultiEvaluator() {
		identifiers = new Vector();
		values = new Vector();
	}

	public Object clone() {
		MultiEvaluator result = new MultiEvaluator();
		result.identifiers = (Vector)identifiers.clone();
		result.values = (Vector)values.clone();
		result.functions = (Hashtable)functions.clone();
		return result;
	}

	public void defineVariable(String name,Part value) {
		identifiers.addElement(name);
		values.addElement(value);
	}

	public java.util.Enumeration variables() {
		return identifiers.elements();
	}

	
 Each undefVariable() annihilates exactly one defineVariable() call.
	  So if you defined a variable multiple times, you have to call
	  undefVariable() exactly as many times as you defineVariable()d it.
	 
	public void undefVariable(String name) {
		int i;

		for (i = values.size(); i-->0; )
			if (name.equals(identifiers.elementAt(i))) {
				identifiers.removeElementAt(i);
				values.removeElementAt(i);
				return;
			}
	}

	/* Returns the value of a previously defined identifier (using
	 * defineVariable()). */
	public Part getValue(String identifier) {
		Double d;
		try { d = new Double(identifier); }
		catch (NumberFormatException exc) {
			for (int i = values.size(); i-->0; )
				if (identifier.equals(identifiers.elementAt(i))) {
					Part result = (Part)values.elementAt(i);
					if (!(result instanceof Identifier)) return result;
					String str = ((Identifier)result).getString();
					try { return new Real(new Double(str).doubleValue()); }
					catch (NumberFormatException ex) { return result; }
				}
			return null;
		}
		return new Real(d.doubleValue());
	}

	
 Change the value of an existing variable. If the variable doesn't
	  exist, this call is equivalent to defineVariable(). 
	public void setValue(String name,Part value) {
		for (int i = values.size(); i-->0; )
			if (name.equals(identifiers.elementAt(i))) {
				// Modify
				values.setElementAt(value,i);
				return;
			}
		// Create
		defineVariable(name,value);
	}

	public void dump() {
		for (int i = values.size()-1; i>=0; i--) {
			System.out.println("---key"+identifiers.elementAt(i));
			Object val = values.elementAt(i);
			if (val instanceof Part)  ((Part)val).dump(1);
			else System.out.println(val);
		}
	}

	public Part call(String funcname,Part args) {
		Function f = (Function)functions.get(funcname);
		if (f == null) return null;
		return f.call(funcname,args,this);
	}

	public void setFunction(String funcname,Function f) {
		functions.put(funcname,f);
	}

	public boolean isFunction(String funcname) {
		return (functions.get(funcname) != null);
	}
}