initial commit

nine/package.json

@@ -0,0 +1,14 @@
+{
+  "name": "nine",
+  "version": "1.0.0",
+  "main": "index.js",
+  "type": "module",
+  "scripts": {
+    "start": "node src/index.js",
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "description": ""
+}

nine/src/automaton.js

@@ -0,0 +1,341 @@
+const seek = value => () => value
+
+export const Seek = Object.freeze({
+    Left: seek(-1),
+    Right: seek(1),
+    Stay: seek(0),
+    First: reader => -reader.position,
+    Last: reader => (reader.length - 1) - reader.position,
+    JumpFromStack: reader => {
+        const state = reader.pop()
+        reader.push()
+        return state.position - reader.position
+    },
+    SeekFromStack: consuming => reader => {
+        const position = (consuming ? reader.peek() : reader.pop()).position
+        return position - reader.position
+    }
+})
+
+export const Predicate = Object.freeze({
+    AnyOf: (...symbols) => b => symbols.includes(b.symbol),
+    Every: (...fns) => x => fns.every(fn => fn(x)),
+    Equals: a => b => a === b.symbol,
+    False: () => false,
+    InBounds: direction => reader => reader.inBounds(reader.position + direction()),
+    Not: fn => x => !fn(x),
+    Number: x => !isNaN(x.symbol),
+    OutOfBounds: direction => reader => !Predicate.InBounds(direction)(reader),
+    Some: (...fns) => x => fns.some(fn => fn(x)),
+    True: () => true,
+})
+
+const tee = fn => x => {
+    fn(x)
+    return x.symbol
+}
+
+export const Replace = Object.freeze({
+    Seq: (...fns) => x => fns.reduce((_acc, fn) => fn(x), x.symbol),
+    With: x => () => x,
+    Nothing: x => x.symbol,
+    Push: x => {
+        x.push()
+        return x.symbol
+    },
+    Pop: x => x.pop(),
+    Swap: x => {
+        const tmp = x.pop()
+        x.push()
+        x.push(tmp)
+        return tmp.symbol
+    },
+    ClearStack: tee(x => x.clear()),
+    FromStack: x => x.peek().symbol,
+    Tee: tee
+})
+
+
+class Head {
+    #position = 0
+
+    get position() { return this.#position }
+
+    left() { this.move(Left) }
+    right() { this.move(Right) }
+    move(value) { this.#position += value }
+
+
+    read(tape) {
+        return tape.at(this.#position)
+    }
+
+    write(tape, value) {
+        tape.write(this.#position, value)
+    }
+}
+
+export class Tape {
+    #value
+
+    constructor(input) {
+        this.#value = Array.isArray(input) ? input : input.split('')
+    }
+
+    get value() { return this.#value }
+    get length() { return this.#value.length }
+
+    at(n) {
+        return this.value[n]
+    }
+
+    write(n, value) {
+        this.#value[n] = value
+    }
+}
+
+export class Rule {
+    constructor(from, to, predicate, replaceSymbol, action) {
+        this.fromState = from
+        this.toState = to
+        this.predicate = predicate
+        this.replaceSymbol = replaceSymbol
+        this.action = action
+    }
+
+    static is(from, to, currentSymbol, nextSymbol, action) {
+        return new Rule(
+            from,
+            to,
+            Predicate.Equals(currentSymbol),
+            nextSymbol,
+            action
+        )
+    }
+}
+
+export class Rules {
+    #firstState
+    #rules = new Map()
+
+    constructor(rules) {
+        this.#firstState = rules[0]
+        this.#initialize(rules)
+    }
+
+    get firstState() { return this.#firstState }
+
+    #initialize(rules) {
+        rules.forEach(rule => {
+            const transition = this.#rules.get(rule.fromState)
+
+            if (transition) {
+                transition.push(rule)
+            } else {
+                this.#rules.set(rule.fromState, [rule])
+            }
+        })
+    }
+
+    get(state, reader) {
+        return this.#rules.get(state)?.find(rule => rule.predicate(reader)) ?? false
+    }
+}
+
+class ReaderState {
+    constructor(position, symbol) {
+        this.position = position
+        this.symbol = symbol
+    }
+
+    static from(reader) {
+        return new ReaderState(reader.position, reader.symbol)
+    }
+}
+
+class Iterator extends Array {
+    #index = 0
+
+    done() {
+        return this.length === 0 || this.#index === this.length - 1
+    }
+
+    peek() {
+        return this[this.#index]
+    }
+
+    next() {
+        return this[this.#index++]
+    }
+
+    take(n) {
+        const result = []
+        while (!this.done() && n--) {
+            result.push(this.next())
+        }
+        return result
+    }
+
+    skip(n) {
+        this.take(n)
+        return this
+    }
+
+    takeUntil(fn) {
+        const result = []
+        let c = 0
+        while (!this.done() && this.peek() && !fn(this.peek())) {
+            result.push(this.next())
+            c++
+        }
+        return result
+    }
+
+    skipUntil(fn) {
+        this.takeUntil(fn)
+        return this
+    }
+}
+
+export class Reader {
+    #head
+    #tape
+    #stack = []
+
+    constructor(head, tape) {
+        this.#head = head
+        this.#tape = tape
+    }
+
+    get head() { return this.#head }
+    get tape() { return this.#tape }
+    get stack() { return Iterator.from(this.#stack) }
+
+    get position() {
+        return this.#head.position
+    }
+
+    get length() {
+        return this.#tape.length
+    }
+
+    get symbol() {
+        return this.#head.read(this.#tape)
+    }
+
+    clear() {
+        this.#stack.length = 0
+    }
+
+    inBounds(index) {
+        return index >= 0 && index <= this.length - 1
+    }
+
+    push(x = ReaderState.from(this)) {
+        this.#stack.push(x)
+    }
+
+    pop() {
+        return this.#stack.pop()
+    }
+
+    peek() {
+        return this.#stack[this.#stack.length - 1]
+    }
+}
+
+const colors = {
+    brightWhite: [97, 107],
+    brightCyan: [96, 106],
+    brightMagenta: [95, 105],
+    brightBlue: [94, 104],
+    brightYellow: [93, 103],
+    brightGreen: [92, 102],
+    brightRed: [91, 101],
+    brightBlack: [90, 100],
+    white: [37, 47],
+    cyan: [36, 46],
+    magenta: [35, 45],
+    blue: [34, 44],
+    yellow: [33, 43],
+    green: [32, 42],
+    red: [31, 41],
+    black: [30, 40],
+}
+
+const color = (code, t) => {
+    if (Array.isArray(code)) {
+        return code.reduce((acc, c) => color(c, acc), t)
+    }
+
+    return `\x1b[${code}m${t}` + (t.endsWith(reset) ? '' : reset)
+}
+const reset = '\x1b[0m'
+//const color = t => `\x1b[44m\x1b[93m${t}\x1b[0m`
+const highlight = (i, arr, col = colors.cyan, spaces = 0) => {
+    const a = arr.slice()
+    const len = a[i].length
+    a[i] = color(col, a[i])
+    const diff = a[i].length - len
+    //console.log(a[i].length, len, diff, spaces)
+    a[i] = a[i].padEnd(spaces + diff)
+    return a
+}
+const range = n => [...Array(n).keys()]
+
+export class TuringMachine {
+    #head = new Head()
+    #rules
+    #state
+    #reader
+
+    constructor(tape, rules, initialState = rules.firstState.fromState, debug = false) {
+        this.tape = tape
+        this.debug = debug
+
+        this.#rules = rules
+        this.#state = initialState
+
+        this.#reader = new Reader(this.#head, this.tape)
+    }
+
+    get state() { return this.#state }
+    get value() { return this.tape.value }
+
+    display(rule, next) {
+        console.log(this.#state, '->', rule.toState, '(', this.#reader.symbol, '->', next, ')')
+        const length = this.tape.length
+        const spaces = length.toString().length + 1
+        console.log(highlight(this.#reader.position, this.value, [1, 2, 4, colors.black[1], colors.yellow[0]], spaces).join(' '.repeat(spaces)))
+        const numbers = range(this.tape.length).map(String)
+        const highlighted = highlight(this.#reader.position, numbers, [1, 7], spaces + 3).map(x => x.padEnd(spaces + 1, ' ')).join('')
+        console.log(highlighted)
+    }
+
+    step(rule) {
+        const next = rule.replaceSymbol(this.#reader)
+
+        if (this.debug) {
+            this.display(rule, next)
+        }
+
+        if (next) {
+            this.#head.write(this.tape, next)
+        }
+        this.#state = rule.toState
+        this.#head.move(rule.action(this.#reader))
+    }
+
+    next() {
+        return this.#rules.get(this.#state, this.#reader)
+    }
+
+    exec() {
+        let next
+        while (next = this.next()) {
+            this.step(next)
+        }
+    }
+}
+
+

nine/src/index.js

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+import { readFile } from 'node:fs/promises'
+import { resolve } from 'node:path'
+import { Rules, Rule, Predicate, Replace, Tape, TuringMachine, Seek } from './automaton.js'
+
+const { First, Last, Left, Right, Stay, SeekFromStack, JumpFromStack } = Seek
+const { ClearStack, Nothing, Push, Seq, Swap, With } = Replace
+const { InBounds, Not, OutOfBounds, True } = Predicate
+
+const State = Object.freeze({
+    Start: 'start',
+    ScanRight: 'scan-right',
+    FindFile: 'find-file',
+    ScanLeft: 'scan-left',
+    FindSpace: 'find-space',
+    ClearFile: 'clear-file',
+})
+
+const IsFreeSpace = Predicate.Equals('.')
+const IsNotFree = Not(IsFreeSpace)
+const IsFartherRight = x => x.peek().position <= x.position
+
+const dot = ch => ch.symbol === '.'
+const notDot = ch => !dot(ch)
+const TrySkipFiles = x => {
+    const stack = x.stack.slice()
+    const a = stack.skipUntil(dot).takeUntil(notDot)
+    const skip = !stack.done()
+    //console.log(a, 'skipping?', skip, !stack.done())
+    return skip
+}
+
+const FirstOrStack = x => {
+    // unwind the stack
+    const states = []
+    let next
+    while (next = x.pop()) {
+        if (next.position < x.position) {
+            break
+        } else {
+            states.push(next)
+            next = null
+        }
+    }
+
+
+    // rewind it
+    states.reverse()
+    let tmp
+    while (tmp = states.pop()) {
+        x.push(tmp)
+    }
+
+    return next ? next : First(x)
+    //return x.peek() ? x.pop().position : First(x)
+}
+
+const TrySkipping = Seq(InBounds(Right), TrySkipFiles)
+
+const HasMoreFiles = x => {
+    const stack = x.stack.slice()
+    stack.skipUntil(dot).skipUntil(notDot)
+    return !stack.done()
+}
+
+const ShouldContinue = Predicate.Every(OutOfBounds(Right), HasMoreFiles)
+
+//        |  From |  To |         Condition             | Next Character | Move Direction |
+//        | ------------------------------------------------------------------------------|
+// new Rule('q0',  'q1', reader => reader.symbol === '1', (_reader) => '0',     1) 
+
+const rules = new Rules([
+    new Rule(State.Start, State.ScanRight, True, Nothing, Right),
+    new Rule(State.ScanRight, State.FindFile, TrySkipping, ClearStack, Last),
+    new Rule(State.ScanRight, State.FindFile, ShouldContinue, ClearStack, Stay),
+    new Rule(State.ScanRight, State.ScanRight, InBounds(Right), Push, Right),
+    new Rule(State.FindFile, State.ScanLeft, IsNotFree, Seq(ClearStack, Push), Stay),
+    new Rule(State.FindFile, State.FindFile, IsFreeSpace, Nothing, Left),
+    new Rule(State.ScanLeft, State.ScanLeft, InBounds(Left), Nothing, FirstOrStack),
+    new Rule(State.ScanLeft, State.FindSpace, OutOfBounds(Left), Nothing, Stay),
+    new Rule(State.FindSpace, State.ScanRight, IsFartherRight, ClearStack, Right),
+    new Rule(State.FindSpace, State.ClearFile, IsFreeSpace, Swap, JumpFromStack),
+    new Rule(State.FindSpace, State.FindSpace, InBounds(Right), Nothing, Right),
+    new Rule(State.ClearFile, State.ScanRight, True, With('.'), SeekFromStack(false)),
+])
+
+const char = x => String.fromCodePoint(x)
+const toInt = x => x.codePointAt() - 32
+const repeat = (n, value) => value.repeat(n)
+
+const expand = input => {
+    return input.split('').reduce((acc, n, i) => {
+        if (i % 2) {
+            return acc.concat(repeat(n, char(46)))
+        } else {
+            return acc.concat(repeat(n, char((i / 2) + 32)))
+        }
+    }, '')
+}
+
+const compress = input => {
+    const tape = new Tape(input)
+    const tm = new TuringMachine(tape, rules)
+    tm.debug = false
+    tm.exec()
+    return tm.value
+}
+
+const notFree = ch => ch !== '.'
+const mul = (a, b) => a * b
+const add = (a, b) => a + b
+
+const checksum = input => input.filter(notFree).map(toInt).map(mul).reduce(add)
+
+const main = input => {
+    const expanded = expand(input)
+    console.log(expanded)
+    const compressed = compress(expanded)
+    console.log(compressed.filter(notFree).map(toInt))
+    const sum = checksum(compressed)
+    return sum
+}
+
+const tests = [
+    ['2333133121414131402', 1928],
+    ['1010101010101010101010', 385],
+    ['111111111111111111111', 290],
+    ['10101010101010101010101', 506],
+    ['90909', 486]
+]
+
+tests.forEach(([input, expected]) => {
+    console.log(`input length is ${input.length}`)
+    const result = main(input)
+    console.log(result === expected, result)
+})
+
+//readFile(resolve('./input'), { encoding: 'utf8' })
+//    .then(x => {
+//        console.log(`input length is ${x.length}`)
+//        return main(x)
+//    })
+//    .then(console.log)
+