quangnle/expgen.html

## expgen.html
<html>
<head>
<title> Expression Generator </title>
<script>

function expr(value, left, op, right, hasParentheses){
	this.value = value;
	this.left = left;
	this.right = right;
	this.op = op;
	this.hasParentheses = hasParentheses;
	var self = this;
	this.toString = function(){
		var result = self.left + " " + self.op + " " + self.right;
		if (self.hasParentheses)
			return "(" + result + ")";
		return result;
	}
};

var add = function(value, hasParentheses) {
	var val = Math.floor(Math.random() * value);
	return new expr(value, val, '+', value - val, hasParentheses);
}

var minus = function(value, hasParentheses) {
	var val = Math.floor(Math.random() * value);
	return new expr(value, value + val, '-', val, hasParentheses);
}

var divide = function(value, hasParentheses) {
	var val = Math.floor(Math.random() * 3) + 1;

	return new expr(value, value * val, '/', val, hasParentheses);
}

var multiply = function(value, hasParentheses) {
	var val = 1;
	var trial = 0;
	do {
		if (trial == 100)
			break;
		val = Math.floor(Math.random() * (value / 2)) + 1;
		trial++;
	} while (value % val != 0);

	return new expr(value, val, '*', value / val, hasParentheses);
}

var ops = ['+', '-', '*', '/'];

var genDict = [add, minus, multiply, divide];

function generate(prevOp, value, level){
	var index = Math.floor(Math.random() * 4);
	var op = ops[index];
	var gen = genDict[index];
	var hasPrnt = Math.floor(ops.indexOf(prevOp) / 2) >= Math.floor(ops.indexOf(op) / 2);

	var newExp = gen(value, hasPrnt);

	if (level == 0)
		return newExp;

	return new expr(value, generate(op, newExp.left, level - 1), op, generate(op, newExp.right, level - 1), hasPrnt);
}


</script>
</head>
<body>
	<button onclick="alert(generate(' ', 15, 1));" >press to generate expression</button>
</body>
</html>
	<html>
	<head>
	<title> Expression Generator </title>
	<script>

	function expr(value, left, op, right, hasParentheses){
	this.value = value;
	this.left = left;
	this.right = right;
	this.op = op;
	this.hasParentheses = hasParentheses;
	var self = this;
	this.toString = function(){
	var result = self.left + " " + self.op + " " + self.right;
	if (self.hasParentheses)
	return "(" + result + ")";
	return result;
	}
	};

	var add = function(value, hasParentheses) {
	var val = Math.floor(Math.random() * value);
	return new expr(value, val, '+', value - val, hasParentheses);
	}

	var minus = function(value, hasParentheses) {
	var val = Math.floor(Math.random() * value);
	return new expr(value, value + val, '-', val, hasParentheses);
	}

	var divide = function(value, hasParentheses) {
	var val = Math.floor(Math.random() * 3) + 1;

	return new expr(value, value * val, '/', val, hasParentheses);
	}

	var multiply = function(value, hasParentheses) {
	var val = 1;
	var trial = 0;
	do {
	if (trial == 100)
	break;
	val = Math.floor(Math.random() * (value / 2)) + 1;
	trial++;
	} while (value % val != 0);

	return new expr(value, val, '*', value / val, hasParentheses);
	}

	var ops = ['+', '-', '*', '/'];

	var genDict = [add, minus, multiply, divide];

	function generate(prevOp, value, level){
	var index = Math.floor(Math.random() * 4);
	var op = ops[index];
	var gen = genDict[index];
	var hasPrnt = Math.floor(ops.indexOf(prevOp) / 2) >= Math.floor(ops.indexOf(op) / 2);

	var newExp = gen(value, hasPrnt);

	if (level == 0)
	return newExp;

	return new expr(value, generate(op, newExp.left, level - 1), op, generate(op, newExp.right, level - 1), hasPrnt);
	}


	</script>
	</head>
	<body>
	<button onclick="alert(generate(' ', 15, 1));" >press to generate expression</button>
	</body>
	</html>