initial commit

experiments/rpncalc-v2/calc.css

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+.stack-box {
+	text-align: center;
+	border: solid 1px black;
+	min-width: 30vmin;
+	max-width: 30vmin; /* will normally be dynamically set */
+	line-height: 30vmin;
+	height: 30vmin;
+	font-size: 7vmin;
+	margin: -1px; /* make edges join neatly */
+}
+
+#input {
+	width: 100%;
+	font-size: 2em;
+}

experiments/rpncalc-v2/calc.js

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+// Reads the input box for a RPN expression
+// Calculates result
+// Outputs it as nicely formatted boxes.
+function calculateFromInput() {
+	var expr = document.getElementById("input").value;
+	var output = document.getElementById("output")
+
+	var result = calculateRPN(expr.split(" "));
+		
+	output.innerHTML = ""; // Clear the output div
+
+	result.stack.forEach(function(num) {
+		num = num.toString().replace("NaN", "Error");
+		var box = createBox(num);
+		box.style["max-width"] = num.length + "em";
+		output.appendChild(box);
+	});
+
+	if (result.errors.length > 0) { // If errors exist output them separated by line breaks.
+			result.errors.forEach(error => {
+				output.appendChild(document.createTextNode(error.toString()))
+				output.appendChild(document.createElement("br"))
+			})
+	}
+}
+
+function add(x, y) {
+	return x + y;
+}
+
+function multiply(x, y) {
+	return x * y;
+}
+
+function divide(x, y) {
+	return x / y;
+}
+
+function flip(x, y) {
+	return [y, x];
+}
+
+function subtract(x, y) {
+	return x - y;
+}
+
+function sum(vals) {
+	var acc = 0;
+
+	vals.forEach(function(el) {
+		acc += el;
+	});
+
+	return acc;
+}
+
+function range(low, high) {
+	var r = [];
+
+	for (var i = low; i <= high; i++) {
+		r.push(i);
+	}
+	
+	return r;
+}
+
+function createBox(contents) {
+	var el = document.createElement("div");
+	el.setAttribute("class", "stack-box");
+
+	el.innerText = contents;
+
+	return el;
+}
+
+// Takes a two-argument function and lifts it to a binary stack op
+function binaryOp(fun) {
+	return function(stack) {
+		var x = stack.pop();
+		var y = stack.pop();
+
+		stack.push(fun(y, x));
+		return stack;
+	}
+}
+
+// Takes a function and lifts it to a unary op using a stack. Returns new stack.
+function unaryOp(fun) {
+	return function(stack) {
+		var x = stack.pop();
+		
+		stack.push(fun(x));
+		return stack;
+	}
+}
+
+// Takes a function and lifts it to an op which takes the entire stack and reduces it to one value. Returns new stack.
+function greedyOp(fun) {
+	return function(stack) {
+		return [fun(stack)];
+	}
+}
+
+// Lifs to an operator which takes two values and adds an array of them to the stack. Returns a new stack.
+function binaryMultioutOp(fun) {
+	return function(stack) {
+		var x = stack.pop();
+		var y = stack.pop();
+		
+		return stack.concat(fun(y, x));
+	}
+}
+
+function calculateRPN(tokens) {
+	var stack = [];
+	var errors = [];
+
+	for (var i = 0; i < tokens.length; i++) {
+		var token = tokens[i];
+
+		switch (token) {
+		case "+":
+			stack = binaryOp(add)(stack);
+			break;
+		case "*":
+			stack = binaryOp(multiply)(stack);
+			break;
+		case "/":
+			stack = binaryOp(divide)(stack);
+			break;
+		case "-":
+			stack = binaryOp(subtract)(stack);
+			break;
+		case "range":
+			stack = binaryMultioutOp(range)(stack);
+			break;
+		case "flip":
+			stack = binaryMultioutOp(flip)(stack);
+			break;
+		case "sum":
+			stack = greedyOp(sum)(stack);
+			break;
+		case "": // This may be entered by accident.
+			break;
+		default:
+			var parsed = parseFloat(token);
+
+			if (parsed === parsed) { // check for NaNs from a failed parse
+				stack.push(parsed);
+			} else {
+				errors.push("Token '" + token + "' (#" + (i + 1) + ")" + " invalid");
+			}
+		}
+	}
+
+	return {stack: stack, errors: errors};
+}

experiments/rpncalc-v2/index.html

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+---
+title: RPNCalc v2
+slug: rpncalc2
+description: A Reverse Polish Notation (check wikipedia) calculator, version 2. Buggy and kind of unreliable. This updated version implements subtraction.
+---
+
+<link rel="stylesheet" href="calc.css">
+
+<center><div id="output"></div></center>
+
+<hr>
+
+<input type="text" id="input" default="Input RPN expression" oninput="calculateFromInput()">
+</div>
+
+<script src="calc.js"></script>