277 lines
7.2 KiB
Markdown
277 lines
7.2 KiB
Markdown
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---
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id: 5d7925381e8565a5c50ba7f1
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title: Step 99
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challengeType: 0
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dashedName: step-99
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---
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# --description--
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In functional programming, we strive to use a type of function called "pure functions" as much as possible. The first property of pure functions is that they always return the same value for the same arguments.
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You can check if this is the case by comparing a call to a function with another call (with the same arguments):
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```js
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console.log(f(2) === f(2)); // always true for pure functions
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```
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Use this technique to check if the `random` function in `spreadsheetFunctions` is pure by passing in the following array: `[1, 1000]`.
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# --hints--
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See description above for instructions.
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```js
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assert(
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/(spreadsheetFunctions\[["']random["']\]\(1,1000\))===\1/.test(
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code.replace(/\s/g, '')
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)
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);
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```
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# --seed--
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## --before-user-code--
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```html
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8">
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<title>Spreadsheet</title>
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<style>
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#container {
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display: grid;
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grid-template-columns: 50px repeat(10, 200px);
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grid-template-rows: repeat(11, 30px);
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}
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.label {
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background-color: lightgray;
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text-align: center;
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vertical-align: middle;
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line-height: 30px;
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}
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</style>
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</head>
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<body>
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<div id="container">
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<div></div>
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</div>
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```
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## --after-user-code--
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```html
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</body>
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</html>
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```
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## --seed-contents--
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```html
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<script>
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const infixToFunction = {
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"+": (x, y) => x + y,
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"-": (x, y) => x - y,
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"*": (x, y) => x * y,
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"/": (x, y) => x / y
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};
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const infixEval = (str, regex) =>
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str.replace(regex, (_, arg1, fn, arg2) =>
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infixToFunction[fn](parseFloat(arg1), parseFloat(arg2))
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);
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const highPrecedence = str => {
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const regex = /([0-9.]+)([*\/])([0-9.]+)/;
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const str2 = infixEval(str, regex);
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return str === str2 ? str : highPrecedence(str2);
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};
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const spreadsheetFunctions = {
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"": x => x,
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random: ([x, y]) => Math.floor(Math.random() * y + x)
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};
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const applyFn = str => {
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const noHigh = highPrecedence(str);
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const infix = /([0-9.]+)([+-])([0-9.]+)/;
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const str2 = infixEval(noHigh, infix);
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const regex = /([a-z]*)\(([0-9., ]*)\)(?!.*\()/i;
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const toNumberList = args => args.split(",").map(parseFloat);
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const applyFunction = (fn, args) =>
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spreadsheetFunctions[fn.toLowerCase()](toNumberList(args));
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return str2.replace(
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regex,
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(match, fn, args) =>
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spreadsheetFunctions.hasOwnProperty(fn.toLowerCase()) ? applyFunction(fn, args) : match
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);
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};
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const range = (start, end) =>
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start > end ? [] : [start].concat(range(start + 1, end));
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const charRange = (start, end) =>
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range(start.charCodeAt(0), end.charCodeAt(0)).map(x =>
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String.fromCharCode(x)
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);
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const evalFormula = x => {
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const rangeRegex = /([A-J])([1-9][0-9]?):([A-J])([1-9][0-9]?)/gi;
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const rangeFromString = (n1, n2) => range(parseInt(n1), parseInt(n2));
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const elemValue = n => c => document.getElementById(c + n).value;
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const addChars = c1 => c2 => n => charRange(c1, c2).map(elemValue(n));
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const varRangeExpanded = x.replace(rangeRegex, (_, c1, n1, c2, n2) =>
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rangeFromString(n1, n2).map(addChars(c1)(c2))
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);
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const varRegex = /[A-J][1-9][0-9]?/gi;
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const varExpanded = varRangeExpanded.replace(
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varRegex,
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match => document.getElementById(match.toUpperCase()).value
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);
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const functionExpanded = applyFn(varExpanded);
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return functionExpanded === x
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? functionExpanded
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: evalFormula(functionExpanded);
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};
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window.onload = () => {
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const container = document.getElementById("container");
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const createLabel = name => {
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const label = document.createElement("div");
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label.className = "label";
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label.textContent = name;
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container.appendChild(label);
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};
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const letters = charRange("A", "J");
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letters.forEach(createLabel);
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range(1, 99).forEach(x => {
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createLabel(x);
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letters.forEach(y => {
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const input = document.createElement("input");
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input.type = "text";
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input.id = y + x;
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input.onchange = update;
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container.appendChild(input);
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});
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});
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};
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const update = event => {
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const element = event.target;
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const value = element.value.replace(/\s/g, "");
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if (!value.includes(element.id) && value[0] === "=") {
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element.value = evalFormula(value.slice(1));
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}
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};
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--fcc-editable-region--
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--fcc-editable-region--
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</script>
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```
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# --solutions--
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```html
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<script>
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const infixToFunction = {
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"+": (x, y) => x + y,
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"-": (x, y) => x - y,
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"*": (x, y) => x * y,
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"/": (x, y) => x / y
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};
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const infixEval = (str, regex) =>
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str.replace(regex, (_, arg1, fn, arg2) =>
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infixToFunction[fn](parseFloat(arg1), parseFloat(arg2))
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);
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const highPrecedence = str => {
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const regex = /([0-9.]+)([*\/])([0-9.]+)/;
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const str2 = infixEval(str, regex);
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return str === str2 ? str : highPrecedence(str2);
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};
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const spreadsheetFunctions = {
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"": x => x,
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random: ([x, y]) => Math.floor(Math.random() * y + x)
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};
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const applyFn = str => {
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const noHigh = highPrecedence(str);
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const infix = /([0-9.]+)([+-])([0-9.]+)/;
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const str2 = infixEval(noHigh, infix);
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const regex = /([a-z]*)\(([0-9., ]*)\)(?!.*\()/i;
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const toNumberList = args => args.split(",").map(parseFloat);
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const applyFunction = (fn, args) =>
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spreadsheetFunctions[fn.toLowerCase()](toNumberList(args));
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return str2.replace(
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regex,
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(match, fn, args) =>
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spreadsheetFunctions.hasOwnProperty(fn.toLowerCase()) ? applyFunction(fn, args) : match
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);
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};
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const range = (start, end) =>
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start > end ? [] : [start].concat(range(start + 1, end));
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const charRange = (start, end) =>
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range(start.charCodeAt(0), end.charCodeAt(0)).map(x =>
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String.fromCharCode(x)
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);
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const evalFormula = x => {
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const rangeRegex = /([A-J])([1-9][0-9]?):([A-J])([1-9][0-9]?)/gi;
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const rangeFromString = (n1, n2) => range(parseInt(n1), parseInt(n2));
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const elemValue = n => c => document.getElementById(c + n).value;
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const addChars = c1 => c2 => n => charRange(c1, c2).map(elemValue(n));
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const varRangeExpanded = x.replace(rangeRegex, (_, c1, n1, c2, n2) =>
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rangeFromString(n1, n2).map(addChars(c1)(c2))
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);
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const varRegex = /[A-J][1-9][0-9]?/gi;
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const varExpanded = varRangeExpanded.replace(
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varRegex,
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match => document.getElementById(match.toUpperCase()).value
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);
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const functionExpanded = applyFn(varExpanded);
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return functionExpanded === x
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? functionExpanded
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: evalFormula(functionExpanded);
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};
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window.onload = () => {
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const container = document.getElementById("container");
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const createLabel = name => {
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const label = document.createElement("div");
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label.className = "label";
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label.textContent = name;
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container.appendChild(label);
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};
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const letters = charRange("A", "J");
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letters.forEach(createLabel);
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range(1, 99).forEach(x => {
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createLabel(x);
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letters.forEach(y => {
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const input = document.createElement("input");
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input.type = "text";
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input.id = y + x;
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input.onchange = update;
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container.appendChild(input);
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});
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});
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};
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const update = event => {
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const element = event.target;
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const value = element.value.replace(/\s/g, "");
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if (!value.includes(element.id) && value[0] === "=") {
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element.value = evalFormula(value.slice(1));
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}
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};
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// console.log(spreadsheetFunctions["random"](1, 1000) === spreadsheetFunctions["random"](1, 1000))
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</script>
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```
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