Function.prototype.bind = function() {

    var func = this;

    var thisObject = arguments[0];

    var args = Array.prototype.slice.call(arguments, 1);

    return function() {

        return func.apply(thisObject, args);

    }

}

//! [0]

function Calculator(ui)

{

    this.ui = ui;

    this.pendingAdditiveOperator = Calculator.NO_OPERATOR;

    this.pendingMultiplicativeOperator = Calculator.NO_OPERATOR;

    this.sumInMemory = 0;

    this.sumSoFar = 0;

    this.factorSoFar = 0;

    this.waitingForOperand = true;

    with (ui) {

        display.text = "0";

        zeroButton.clicked.connect(this.digitClicked.bind(this, 0));

        oneButton.clicked.connect(this.digitClicked.bind(this, 1));

        twoButton.clicked.connect(this.digitClicked.bind(this, 2));

        threeButton.clicked.connect(this.digitClicked.bind(this, 3));

        fourButton.clicked.connect(this.digitClicked.bind(this, 4));

        fiveButton.clicked.connect(this.digitClicked.bind(this, 5));

        sixButton.clicked.connect(this.digitClicked.bind(this, 6));

        sevenButton.clicked.connect(this.digitClicked.bind(this, 7));

        eightButton.clicked.connect(this.digitClicked.bind(this, 8));

        nineButton.clicked.connect(this.digitClicked.bind(this, 9));

        pointButton.clicked.connect(this, "pointClicked");

        changeSignButton.clicked.connect(this, "changeSignClicked");

        backspaceButton.clicked.connect(this, "backspaceClicked");

        clearButton.clicked.connect(this, "clear");

        clearAllButton.clicked.connect(this, "clearAll");

        clearMemoryButton.clicked.connect(this, "clearMemory");

        readMemoryButton.clicked.connect(this, "readMemory");

        setMemoryButton.clicked.connect(this, "setMemory");

        addToMemoryButton.clicked.connect(this, "addToMemory");

        divisionButton.clicked.connect(this.multiplicativeOperatorClicked.bind(this, Calculator.DIVISION_OPERATOR));

        timesButton.clicked.connect(this.multiplicativeOperatorClicked.bind(this, Calculator.TIMES_OPERATOR));

        minusButton.clicked.connect(this.additiveOperatorClicked.bind(this, Calculator.MINUS_OPERATOR));

        plusButton.clicked.connect(this.additiveOperatorClicked.bind(this, Calculator.PLUS_OPERATOR));

        squareRootButton.clicked.connect(this.unaryOperatorClicked.bind(this, Calculator.SQUARE_OPERATOR));

        powerButton.clicked.connect(this.unaryOperatorClicked.bind(this, Calculator.POWER_OPERATOR));

        reciprocalButton.clicked.connect(this.unaryOperatorClicked.bind(this, Calculator.RECIPROCAL_OPERATOR));

        equalButton.clicked.connect(this, "equalClicked");

    }

}

//! [0]

Calculator.NO_OPERATOR = 0;

Calculator.SQUARE_OPERATOR = 1;

Calculator.POWER_OPERATOR = 2;

Calculator.RECIPROCAL_OPERATOR = 3;

Calculator.DIVISION_OPERATOR = 4;

Calculator.TIMES_OPERATOR = 5;

Calculator.MINUS_OPERATOR = 6;

Calculator.PLUS_OPERATOR = 7;

Calculator.prototype.abortOperation = function()

{

    this.clearAll();

    this.ui.display.text = "####";

}

Calculator.prototype.calculate = function(rightOperand, pendingOperator)

{

    if (pendingOperator == Calculator.PLUS_OPERATOR) {

        this.sumSoFar += rightOperand;

    } else if (pendingOperator == Calculator.MINUS_OPERATOR) {

        this.sumSoFar -= rightOperand;

    } else if (pendingOperator == Calculator.TIMES_OPERATOR) {

        this.factorSoFar *= rightOperand;

    } else if (pendingOperator == Calculator.DIVISION_OPERATOR) {

        if (rightOperand == 0)

            return false;

        this.factorSoFar /= rightOperand;

    }

    return true;

}

//! [1]

Calculator.prototype.digitClicked = function(digitValue)

{

    if ((digitValue == 0) && (this.ui.display.text == "0"))

        return;

    if (this.waitingForOperand) {

        this.ui.display.clear();

        this.waitingForOperand = false;

    }

    this.ui.display.text += digitValue;

}

//! [1]

Calculator.prototype.unaryOperatorClicked = function(op)

{

    var operand = this.ui.display.text - 0;

    var result = 0;

    if (op == Calculator.SQUARE_OPERATOR) {

        if (operand < 0) {

            this.abortOperation();

            return;

        }

        result = Math.sqrt(operand);

    } else if (op == Calculator.POWER_OPERATOR) {

        result = Math.pow(operand, 2);

    } else if (op == Calculator.RECIPROCAL_OPERATOR) {

        if (operand == 0.0) {

            this.abortOperation();

            return;

        }

        result = 1 / operand;

    }

    this.ui.display.text = result + "";

    this.waitingForOperand = true;

}

Calculator.prototype.additiveOperatorClicked = function(op)

{

    var operand = this.ui.display.text - 0;

    if (this.pendingMultiplicativeOperator != Calculator.NO_OPERATOR) {

        if (!this.calculate(operand, this.pendingMultiplicativeOperator)) {

            this.abortOperation();

            return;

        }

        this.ui.display.text = this.factorSoFar + "";

        operand = this.factorSoFar;

        this.factorSoFar = 0;

        this.pendingMultiplicativeOperator = Calculator.NO_OPERATOR;

    }

    if (this.pendingAdditiveOperator != Calculator.NO_OPERATOR) {

        if (!this.calculate(operand, this.pendingAdditiveOperator)) {

            this.abortOperation();

            return;

        }

        this.ui.display.text = this.sumSoFar + "";

    } else {

        this.sumSoFar = operand;

    }

    this.pendingAdditiveOperator = op;

    this.waitingForOperand = true;

}

Calculator.prototype.multiplicativeOperatorClicked = function(op)

{

    var operand = this.ui.display.text - 0;

    if (this.pendingMultiplicativeOperator != Calculator.NO_OPERATOR) {

        if (!this.calculate(operand, this.pendingMultiplicativeOperator)) {

            this.abortOperation();

            return;

        }

        this.ui.display.text = this.factorSoFar + "";

    } else {

        this.factorSoFar = operand;

    }

    this.pendingMultiplicativeOperator = op;

    this.waitingForOperand = true;

}

Calculator.prototype.equalClicked = function()

{

    var operand = this.ui.display.text - 0;

    if (this.pendingMultiplicativeOperator != Calculator.NO_OPERATOR) {

        if (!this.calculate(operand, this.pendingMultiplicativeOperator)) {

            this.abortOperation();

            return;

        }

        operand = this.factorSoFar;

        this.factorSoFar = 0.0;

        this.pendingMultiplicativeOperator = Calculator.NO_OPERATOR;

    }

    if (this.pendingAdditiveOperator != Calculator.NO_OPERATOR) {

        if (!this.calculate(operand, this.pendingAdditiveOperator)) {

            this.abortOperation();

            return;

        }

        this.pendingAdditiveOperator = Calculator.NO_OPERATOR;

    } else {

        this.sumSoFar = operand;

    }

    this.ui.display.text = this.sumSoFar + "";

    this.sumSoFar = 0.0;

    this.waitingForOperand = true;

}

Calculator.prototype.pointClicked = function()

{

    if (this.waitingForOperand)

        this.ui.display.text = "0";

    if (this.ui.display.text.indexOf(".") == -1)

        this.ui.display.text += ".";

    this.waitingForOperand = false;

}

//! [2]

Calculator.prototype.changeSignClicked = function()

{

    var text = this.ui.display.text;

    var value = text - 0;

    if (value > 0) {

        text = "-" + text;

    } else if (value < 0) {

        text = text.slice(1);

    }

    this.ui.display.text = text;

}

//! [2]

Calculator.prototype.backspaceClicked = function()

{

    if (this.waitingForOperand)

        return;

    var text = this.ui.display.text;

    text = text.slice(0, -1);

    if (text.length == 0) {

        text = "0";

        this.waitingForOperand = true;

    }

    this.ui.display.text = text;

}

Calculator.prototype.clear = function()

{

    if (this.waitingForOperand)

        return;

    this.ui.display.text = "0";

    this.waitingForOperand = true;

}

Calculator.prototype.clearAll = function()

{

    this.sumSoFar = 0.0;

    this.factorSoFar = 0.0;

    this.pendingAdditiveOperator = Calculator.NO_OPERATOR;

    this.pendingMultiplicativeOperator = Calculator.NO_OPERATOR;

    this.ui.display.text = "0";

    this.waitingForOperand = true;

}

Calculator.prototype.clearMemory = function()

{

    this.sumInMemory = 0.0;

}

Calculator.prototype.readMemory = function()

{

    this.ui.display.text = this.sumInMemory + "";

    this.waitingForOperand = true;

}

Calculator.prototype.setMemory = function()

{

    this.equalClicked();

    this.sumInMemory = this.ui.display.text - 0;

}

Calculator.prototype.addToMemory = function()

{

    this.equalClicked();

    this.sumInMemory += this.ui.display.text - 0;

}