class Op
	{
	
	private static final char ADD = '+';
	private static final char DIV = '/';
	private static final char MUL = '*';
	private static final char SUB = '-';
	private static final char NEG = '±';
	
	private char op;
	
	private Op( char op )
		{ this.op = op; }
		
	private char op()
		{ return this.op; }
	
	
	String asString()
		{
		char[] str = { op }; 
		return new String( str );
		}
			
	static Op Add()
		{ return new Op( ADD ); }
		
	static Op Divide()
		{ return new Op( DIV ); }
		
	static Op Multiply()
		{ return new Op( MUL ); }
		
	static Op Negate()
		{ return new Op( NEG); }
		
	static Op Subtract()
		{ return new Op( SUB ); }

		
	boolean isAddition()
		{ return op() == ADD; }
				
	boolean isDivision()
		{ return op() == DIV; }
		
	boolean isMultiplication()
		{ return op() == MUL; }
	
	boolean isNegation()
		{ return op() == NEG; }
				
	boolean isSubtraction()
		{ return op() == SUB; }	
		
	boolean isBinaryOp()
		{ return ( ! isUnaryOp() ); }
	
	boolean isUnaryOp()
		{ return isNegation(); }

	
	Double perform( Double a )
		{
		double temp = a.doubleValue();
		double result = Double.NaN;
		
		if ( isNegation() )
		 	{ result = temp * -1d; };
		return new Double( result );
		}
	
	Double perform( Double a, Double b )
		{
		double temp1 = a.doubleValue();
		double temp2 = b.doubleValue();
		double result = Double.NaN;
		
		if ( isAddition() )
		 	{ result = temp1 + temp2; }
		else if ( isSubtraction() )
			{ result = temp1 - temp2; }
		else if ( isMultiplication() )
			{ result = temp1 * temp2; }
		else if ( isDivision() )
			{ result = temp1 / temp2; };
			
		return new Double( result );
		}
		
	}