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| type Char = string; | |
| type Decimal = number; | |
| type NextArgs<I, O, C> = (input: I, accumulation: O, context?: C) => { input: I, accumulation: O }; | |
| class RecursiveIterator<I, O, C=unknown> { | |
| private context: C; | |
| private next: NextArgs<I, O, C>; | |
| private shouldReturn: (i: I) => boolean; | |
| private initializeAccumulation: () => O; | |
| constructor(params: { | |
| context?: C, | |
| next: NextArgs<I, O, C>; | |
| shouldReturn: (i: I) => boolean, | |
| initializeAccumulation: () => O, | |
| }) { | |
| this.next = params.next; | |
| this.context = params.context; | |
| this.shouldReturn = params.shouldReturn; | |
| this.initializeAccumulation = params.initializeAccumulation; | |
| } | |
| private recursion(input: I, accumulation: O) { | |
| if (this.shouldReturn(input)) { | |
| return accumulation; | |
| } | |
| const nextArgs = this.next(input, accumulation, this.context); | |
| return this.recursion(nextArgs.input, nextArgs.accumulation); | |
| } | |
| public iterate(input: I): O { | |
| return this.recursion(input, this.initializeAccumulation()); | |
| } | |
| } | |
| type EncoderContext = { base: number, encode: (n: Decimal) => Char }; | |
| type DecoderContext = { base: number, decode: (c: Char) => Decimal }; | |
| class DecimalConverter { | |
| constructor( | |
| private encodeIterator: RecursiveIterator<Decimal, string, EncoderContext>, | |
| private decodeIterator: RecursiveIterator<string, Decimal, DecoderContext>, | |
| ) { | |
| } | |
| public decode(input: string): Decimal { | |
| return this.decodeIterator.iterate(input); | |
| } | |
| public encode(input: Decimal): string { | |
| return this.encodeIterator.iterate(input); | |
| } | |
| } | |
| const EXCEL_COLUMN_BASE = 26; | |
| const EXCEL_COLUMN_CHAR_CODE_OFFSET = 'A'.charCodeAt(0) - 1; | |
| const excelColumnDecimalConverter = new DecimalConverter( | |
| new RecursiveIterator({ | |
| shouldReturn: i => i === 0, | |
| initializeAccumulation: () => '', | |
| context: { | |
| base: EXCEL_COLUMN_BASE, | |
| encode: n => String.fromCharCode(n + EXCEL_COLUMN_CHAR_CODE_OFFSET), | |
| }, | |
| next: (i, a, c) => ({ | |
| input: Math.floor(i / c.base), | |
| accumulation: c.encode(i % c.base) + a, | |
| }), | |
| }), | |
| new RecursiveIterator({ | |
| initializeAccumulation: () => 0, | |
| shouldReturn: i => i.length === 0, | |
| context: { | |
| base: EXCEL_COLUMN_BASE, | |
| decode: c => c.charCodeAt(0) - EXCEL_COLUMN_CHAR_CODE_OFFSET, | |
| }, | |
| next: (i, a, c) => ({ | |
| input: i.slice(1, i.length), | |
| accumulation: a * c.base + c.decode(i[0]), | |
| }), | |
| }), | |
| ); | |
| console.log(excelColumnDecimalConverter.decode('AMJ')); | |
| console.log(excelColumnDecimalConverter.encode(1024)); |
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