public NLInterpreter() {
		operators = new HashMap<String, Character>();
		// secondaryOperators = new HashMap<String, String>();
		operands = new HashMap<String, Integer>();

		operators.put("plus", 			'+');
		operators.put("minus", 			'-');
		operators.put("times", 			'*');
		operators.put("multiply", 		'*');
		operators.put("multiply by",	'*');
		operators.put("multiplied by", 	'*');
		operators.put("x", 				'*');
		operators.put("X", 				'*');
		operators.put("divide", 		'/');
		operators.put("divided by", 	'/');
		operators.put("divide by", 		'/');
		operators.put("over", 			'/');
		operators.put("modulus", 		'%');
		operators.put("mod",			'%');
		operators.put("to the power of",'^');
		operators.put("tothepowerof",   '^');
		operators.put("sqrt",			'√');
		operators.put("square root",	'√');
		operators.put("squareroot",		'√');

		/*
		secondaryOperators.put("squared", "to the power of two");
		secondaryOperators.put("cubed", "to the power of three");
		*/

		operands.put("zero",		0);
		operands.put("one", 		1);
		operands.put("two", 		2);
		operands.put("three", 		3);
		operands.put("four", 		4);
		operands.put("five", 		5);
		operands.put("six", 		6);
		operands.put("seven", 		7);
		operands.put("eight", 		8);
		operands.put("nine", 		9);
		operands.put("ten", 		10);
		operands.put("eleven", 		11);
		operands.put("twelve", 		12);
		operands.put("thirteen", 	13);
		operands.put("fourteen", 	14);
		operands.put("fifteen", 	15);
		operands.put("sixteen", 	16);
		operands.put("seventeen",	17);
		operands.put("eighteen", 	18);
		operands.put("nineteen", 	19);
		operands.put("twenty", 		20);
		operands.put("thirty", 		30);
		operands.put("forty", 		40);
		operands.put("fifty", 		50);
		operands.put("sixty", 		60);
		operands.put("seventy", 	70);
		operands.put("eighty", 		80);
		operands.put("ninety", 		90);
		operands.put("hundred", 	100);
		operands.put("thousand",	1000);
		operands.put("million", 	1000000);
		operands.put("billion",		1000000000);
		// Points are handled explicitly in evaluateOperand()
		operands.put("point",		-1); 
		operands.put(".",			-1);
	}