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