init

.vscode/launch.json

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+{
+	// Use IntelliSense to learn about possible attributes.
+	// Hover to view descriptions of existing attributes.
+	// For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+	"version": "0.2.0",
+	"configurations": [
+		{
+			"type": "node",
+			"request": "launch",
+			"name": "Launch Program",
+			"program": "${workspaceFolder}/example.js"
+		}
+	]
+}

example.js

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+const infiniteList = require('.');
+
+const increment = i => i + 2;
+const infinite = infiniteList.create(0, increment, 10);
+
+// infinite;
+console.log(infinite.top())
+console.log(infinite.last())
+
+console.log(infinite.get(5))
+console.log(infinite.get(5))
+console.log(infinite.get(6))
+console.log(infinite.get(14).next())
+
+console.log(infinite.toString())
+console.log(infinite.top().next().next().toString())
+
+console.log(infinite.take(5))
+
+const gen = infinite[Symbol.iterator];
+gen();
+
+for(let i of infinite) {
+	// if(i.index > 100) break;
+	// console.log(infinite.get(5).value);
+	console.log(i.value.toString());
+}

index.js

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+const always = x => _ => x;
+
+const infiniteList = {
+	/**
+	 * InfiniteList Constructor. Iterates infinitely until index value is found.
+	 * 
+	 * @param {any} start 
+	 * @param {any} next 
+	 * @param {any} limit 
+	 * @returns 
+	 */
+	create (start, next, limit) {
+
+		// Closure magic!
+		const cache = [];
+		let j = 0;
+
+		// Get list item of index i
+		function get(i) {
+
+			// Validation
+			if(
+				// i is a falsy value except 0
+				(!i && i !== 0)
+				// is not a number
+				|| (typeof i !== 'number')
+				// is... not a number
+				|| Number.isNaN(i)
+			) return;
+
+			// Cache limiting. If cache becomes larger
+			// than limit, deletes non-empty first item
+			//TODO: FIX: Does not minCache is always 1,
+			// and cache length doesn't decrease more than 1
+			let minCache;
+			if (cache.length > (limit || 10000))
+				for (const cacheIndex in cache) {
+					delete cache[cacheIndex];
+					minCache = cacheIndex + 1;
+					break;
+				}
+
+			// Initializing first item if it doesn't exist
+			if(!cache[0]) cache[0] = start;
+
+			// Create returnable object
+			const obj = {
+					next: () => this.get(i+1),
+					previous: () => this.get(i - 1),
+					[Symbol.iterator]: () => ({
+						next: () => ({
+							done: false,
+							value: this.get(i+1)
+						})
+					}),
+					toString: () => {
+						const val = get(i).value;
+						return ( 'InfiniteLinkedListItem [ ..., '
+							+ ((typeof val === 'object' && val !== null)
+								? JSON.stringify(val, null, 2)
+								: val.toString())
+							+ ', ... ]' )
+					}
+				}
+
+			// If index were to be infinity, value and index are infinity
+			if(i === Infinity) {
+				obj.value = Infinity;
+				obj.index = Infinity;
+				return obj;
+			}
+
+			// If index exists in cache, return the value
+			if(i in cache) {
+				obj.value = cache[i];
+				obj.index = i;
+				return obj;
+			}
+
+			// If i doesn't exist in cache // Only works in forward
+			//TODO: FIX
+			if(!(i in cache)) {
+				if(cache.length <= i && (cache.length - 1) in cache)
+					while (cache.length <= i)
+						cache[cache.length] = next(cache[cache.length - 1]);
+			}
+			obj.value = cache[i];
+			obj.index = i;
+			return obj;
+		}
+
+		const take = (from, to) => {
+			const arr = [];
+			let source, target;
+			if(!to) { source = 0; target = from; }
+			else ({ from: source, to: target} = { from, to });
+			for(let i = source; i < target; i ++) {
+				arr.push(get(i));
+			};
+			return arr;
+		};
+
+		top = function () { return this.get(0) };
+		end = function () { return this.get(Infinity) };
+		const returns = {
+			get,
+			take,
+			top,
+			first: top,
+			end,
+			last: end,
+			[Symbol.iterator]: () => ({
+				next: () => ({
+					done: false,
+					value: get(j++)
+				})
+			}),
+			toString: () => 'InfiniteLinkedList [ ' + take(0, 10).map(x => (' ' + x.value.toString())) + ' ... ]'
+		};
+		return returns;
+	}
+}
+
+module.exports = infiniteList;

package.json

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+{
+  "name": "@codefeathers/infinite",
+  "version": "0.1.0",
+  "description": "Infinitely generating linked list with memoisation (or an n-generator)",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "keywords": [
+    "infinite",
+    "list",
+    "data structure",
+    "datatypes",
+    "generators"
+  ],
+  "author": "Muthu Kumar <@MKRhere> (https://mkr.pw)",
+  "license": "MIT"
+}