add error handling for "too few elements on stack". (44dc983d) · Commits · Yuanle Song / rpn-calculator

calc.html

+56 −6

Original line number	Diff line number	Diff line
		@@ -54,6 +54,10 @@
		border: 1px grey solid;
		width: 100%;
		text-align: right;
		font-size: 1.5em;
		}
		#error-msg {
		height: 30px;
		}
		</style>
		</head>
		@@ -69,7 +73,10 @@
		<div class="keyboard">
		<table>
		<tr>
		<td colspan="4" data-bt-name="number-display" id="number-display"></td>
		<td colspan="4" id="error-msg"></td>
		</tr>
		<tr>
		<td colspan="4" id="number-display"></td>
		</tr>
		<tr>
		<td data-bt-name="num7">7</td>
		@@ -216,6 +223,22 @@
		console.assert(m.numberStack[0] === -9);
		console.assert(m.numberStack[1] === 29 * 2);
		};
		const rpnBackspaceOperator = function () {
		const m = new fsm.RPNCalculator();
		m.sendKey("num1");
		m.sendKey("num2");
		console.assert(m.currentNumber === "12");
		m.sendKey("backspace"); // remove last digit in current number.
		console.assert(m.currentNumber === "1");
		m.sendKey("num3");
		m.sendKey("return");
		console.assert(m.currentNumber === "");
		console.assert(m.numberStack.length === 1);
		console.assert(m.numberStack[0] === 13);

		m.sendKey("backspace"); // delete last number in stack.
		console.assert(m.numberStack.length === 0);
		};
		const rpnTestNumberErrorHandling = function () {
		var m = new fsm.RPNCalculator();
		m.sendKey("num0");
		@@ -244,6 +267,29 @@
		m.sendKey("return");
		console.assert(m.numberStack[0] === 1.23);
		};
		const rpnTestNotEnoughElementOnStack = function () {
		const m = new fsm.RPNCalculator();
		console.assert(m.numberStack.length === 0);
		m.sendKey("num1");
		m.sendKey("return");
		console.assert(m.numberStack.length === 1);
		console.assert(m.numberStack[0] === 1);
		m.sendKey("plus");
		console.assert(m.numberStack.length === 1);
		console.assert(m.numberStack[0] === 1);
		console.assert(m.lastError !== null);
		m.sendKey("backspace");
		console.assert(m.numberStack.length === 0);
		console.assert(m.lastError === null);
		m.sendKey("change-sign");
		console.assert(m.lastError !== null);
		m.sendKey("num1");
		console.assert(m.lastError === null);
		m.sendKey("change-sign");
		console.assert(m.numberStack.length === 1);
		console.assert(m.numberStack[0] === -1);
		console.assert(m.lastError === null);
		};

		/**
		* run all tests.
		@@ -266,6 +312,8 @@
		rpnTestOperator();

		rpnTestNumberErrorHandling();
		rpnTestNotEnoughElementOnStack();
		rpnBackspaceOperator();
		};

		/**
		@@ -275,6 +323,7 @@
		*/
		const updateUI = function (rpnCalculator) {
		$('#number-display').text(rpnCalculator.currentNumber);
		$('#error-msg').text(rpnCalculator.lastError);
		const stack = rpnCalculator.numberStack;
		const stackSize = stack.length;
		$("#stack-content").children().remove();
		@@ -299,11 +348,12 @@
		var i;
		const target = evt.target;
		const keyName = $(target).attr('data-bt-name');
		if (keyName !== undefined) {
		console.log("user clicked on button: " + keyName);
		rpnCalculator.sendKey(keyName);

		// update UI
		updateUI(rpnCalculator);
		}
		});
		}());
		</script>

fsm.js

+88 −10

Original line number	Diff line number	Diff line
		@@ -101,6 +101,7 @@ var fsm = function () {
		"return": "return",
		change_sign: "change-sign",
		};
		const msgTooFewElementsOnStack = "Too few elements on stack";

		this.currentState = stateIdle;
		this.numberStack = [];
		@@ -132,13 +133,53 @@ var fsm = function () {
		console.log(msg);
		this.lastError = msg;
		};
		/**
		* clear error msg.
		*/
		this.clearErrorMsg = function () {
		this.lastError = null;
		};
		/**
		* do calculation for a binary operator.
		* this handles not enough element in stack problem.
		*
		* it may modify this.numberStack and this.lastError.
		*
		* Return true on success, return false on failure.
		* You may do early return if this function fails. this.lastError will
		* be set when false is returned.
		*/
		this.doBinaryOperator = function (func) {
		const num2 = this.numberStack.pop();
		if (num2 === undefined) {
		this.setErrorMsg(msgTooFewElementsOnStack);
		return false;
		}
		const num1 = this.numberStack.pop();
		if (num1 === undefined) {
		this.setErrorMsg(msgTooFewElementsOnStack);
		this.numberStack.push(num2);
		return false;
		}
		const result = func(num1, num2);
		if (result === undefined \|\| result === null \|\| result === false) {
		// this does consume the two numbers. Just don't push result
		// to number stack.
		if (this.lastError === null) {
		this.setErrorMsg("result of this operator is undefined or null");
		}
		return false;
		}
		this.numberStack.push(result);
		return true;
		};

		/**
		* return true if given keyName is one of number keys.
		* number keys include num0-9 and dot.
		*/
		const isNumberKey = function (keyName) {
		return keyName.startsWith("num") \|\| keyName === keyNames.dot;
		return (keyNames[keyName] !== undefined) && (keyName.startsWith("num") \|\| keyName === keyNames.dot);
		};
		/**
		* operator key names.
		@@ -233,36 +274,72 @@ var fsm = function () {
		} else {
		switch (keyName) {
		case keyNames.plus:
		this.numberStack.push(this.numberStack.pop() + this.numberStack.pop());
		if (! this.doBinaryOperator((lhs, rhs) => lhs + rhs)) {
		return;
		}
		break;
		case keyNames.minus:
		num2 = this.numberStack.pop();
		num1 = this.numberStack.pop();
		this.numberStack.push(num1 - num2);
		if (! this.doBinaryOperator((lhs, rhs) => lhs - rhs)) {
		return;
		}
		break;
		case keyNames.change_sign:
		this.numberStack.push(-this.numberStack.pop());
		num = this.numberStack.pop();
		if (num === undefined) {
		this.setErrorMsg(msgTooFewElementsOnStack);
		return;
		}
		this.numberStack.push(-num);
		break;
		case keyNames.times:
		this.numberStack.push(this.numberStack.pop() * this.numberStack.pop());
		if (! this.doBinaryOperator((lhs, rhs) => lhs * rhs)) {
		return;
		}
		break;
		case keyNames.divide:
		num2 = this.numberStack.pop();
		num1 = this.numberStack.pop();
		this.numberStack.push(num1 / num2);
		if (! this.doBinaryOperator((lhs, rhs) => {
		if (rhs === 0) {
		this.setErrorMsg("Division by 0");
		return null;
		}
		return lhs / rhs;
		})) {
		return;
		}
		break;
		case keyNames.swap:
		num2 = this.numberStack.pop();
		if (num2 === undefined) {
		this.setErrorMsg(msgTooFewElementsOnStack);
		return;
		}
		num1 = this.numberStack.pop();
		if (num1 === undefined) {
		this.setErrorMsg(msgTooFewElementsOnStack);
		this.numberStack.push(num2);
		return;
		}
		this.numberStack.push(num2);
		this.numberStack.push(num1);
		break;
		case keyNames['return']:
		// duplicate number
		num = this.numberStack.pop();
		if (num === undefined) {
		this.setErrorMsg(msgTooFewElementsOnStack);
		return;
		}
		this.numberStack.push(num);
		this.numberStack.push(num);
		break;
		case keyNames.backspace:
		// drop one number on stack
		num = this.numberStack.pop();
		if (num === undefined) {
		this.setErrorMsg(msgTooFewElementsOnStack);
		return;
		}
		break;
		default:
		console.assert(false, "action not implemented, key is " + keyName);
		}
		@@ -309,6 +386,7 @@ var fsm = function () {
		console.assert(false, "unknown state: " + this.currentState);
		}
		debug("sendKey " + keyName + ", currentState is " + this.currentState);
		this.clearErrorMsg();
		return this.currentState;
		};

operational

+31 −6

Original line number	Diff line number	Diff line
		@@ -23,6 +23,7 @@ Time-stamp: <2017-01-27>
		\| waiting for number or action \| press +-*/ \| commit number, do op, then idle \|
		\| waiting for number or action \| press < key \| modify number, then waiting for number or action \|
		\| idle \| press return key \| dup number, then idle \|
		\| idle \| press < key \| drop number on stack, then idle \|

		There is no ending state, the machine can always accept new keyboard events.

		@@ -47,8 +48,6 @@ the parent DOM.

		* current :entry:
		**
		** 2017-01-26 handle error for every this.numberStack.pop()

		** 2017-01-26 make trail persistent
		trail is a sized fifo queue, it just store recent 1k entries.
		when multiple instances of calculator is working. they all write to a single
		@@ -56,14 +55,40 @@ trail cache. it's not a problem.

		** 2017-01-26 make it work offline, add sw.js
		** 2017-01-26 make undo work
		** 2017-01-26 make stack auto numbering work
		** 2017-01-26 make < (backspace) work.
		** 2017-01-26 make basic things work.
		- DONE draw the keyboard using HTML and CSS
		- make basic number input and arithmetic work
		- make DUP and SWP work
		- DONE make basic number input and arithmetic work
		- DONE make DUP and SWP work
		- make trail work
		* done :entry:
		** 2017-01-26 make < (backspace) work.
		** 2017-01-26 make stack auto numbering work
		** 2017-01-26 handle error for every this.numberStack.pop()
		- handle error for every this.numberStack.pop()
		- show lastError in web UI.

		RPNCalculator should clear lastError when it processed another sendKey()
		successfully.

		maybe do early return whenever I called this.setErrorMsg(errMsg).

		- implementation notes
		- [].pop() return undefined when array is empty.

		- when fetch 2 values, if only 1 fail. the pop() number should be put back
		to the stack. add a unit test for this.

		- about division by 0. js just return infinity.
		I will show error instead and do not consume any number on stack.

		** 2017-01-27 feature: backspace key, when idle, should delete number on stack.
		** 2017-01-27 bug: press number-display button trigger an error.
		it is treated as a num key.

		the FSM should only accept known keys.

		update isNumberKey().

		** 2017-01-26 make basic number input and arithmetic work
		- DONE make event work.
		- TODO add some visual feedback when clicking a button. like in material design.