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https://github.com/y9san9/aoc23
Solving Advent of Code in pure Kotlin without use of mutability
https://github.com/y9san9/aoc23
Last synced: 5 days ago
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Solving Advent of Code in pure Kotlin without use of mutability
- Host: GitHub
- URL: https://github.com/y9san9/aoc23
- Owner: y9san9
- Created: 2023-12-01T16:27:02.000Z (12 months ago)
- Default Branch: master
- Last Pushed: 2023-12-12T10:32:47.000Z (11 months ago)
- Last Synced: 2023-12-12T11:29:59.174Z (11 months ago)
- Language: Kotlin
- Size: 228 KB
- Stars: 5
- Watchers: 1
- Forks: 0
- Open Issues: 0
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Metadata Files:
- Readme: README.md
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README
# Advent Of Code 2023
## Restrictions
- 
- No [mutable state](#immutability) **at all** (`var` variables, mutable lists, etc.)
- To be done...
## Navigation
- Day 1
- [Part 1](src/main/kotlin/me/y9san9/aoc23/day1/part1/Day1.1.kt)
- [Part 2](src/main/kotlin/me/y9san9/aoc23/day1/part2/Day1.2.kt)
- Day 2
- [Part 1](src/main/kotlin/me/y9san9/aoc23/day2/part1/Day2.1.kt)
- [Part 2](src/main/kotlin/me/y9san9/aoc23/day2/part2/Day2.2.kt)
- Day 3
- [Part 1](src/main/kotlin/me/y9san9/aoc23/day3/part1/Day3.1.kt)
- [Part 2](src/main/kotlin/me/y9san9/aoc23/day3/part2/Day3.2.kt)
- Day 4
- [Part 1](src/main/kotlin/me/y9san9/aoc23/day4/part1/Day4.1.kt)
- [Part 2](src/main/kotlin/me/y9san9/aoc23/day4/part2/Day4.2.kt)
- Day 5
- [Part 1](src/main/kotlin/me/y9san9/aoc23/day5/part1/Day5.1.kt)
- [Part 2](src/main/kotlin/me/y9san9/aoc23/day5/part2/Day5.2.kt)
- Day 6
- [Part 1](src/main/kotlin/me/y9san9/aoc23/day6/part1/Day6.1.kt)
- [Part 2](src/main/kotlin/me/y9san9/aoc23/day6/part2/Day6.2.kt)
- Day 7
- [Part 1](src/main/kotlin/me/y9san9/aoc23/day7/part1/Day7.1.kt)
- [Part 2](src/main/kotlin/me/y9san9/aoc23/day7/part2/Day7.2.kt)
- Day 8
- [Part 1](src/main/kotlin/me/y9san9/aoc23/day8/part1/Day8.1.kt)
- [Part 2](src/main/kotlin/me/y9san9/aoc23/day8/part2/Day8.2.kt)
- Day 9
- [Part 1](src/main/kotlin/me/y9san9/aoc23/day9/part1/Day9.1.kt)
- [Part 2](src/main/kotlin/me/y9san9/aoc23/day9/part2/Day9.2.kt)
- Day 10
- [Part 1](src/main/kotlin/me/y9san9/aoc23/day10/part1/Day10.1.kt)
- [Part 2](src/main/kotlin/me/y9san9/aoc23/day10/part2/Day10.2.kt)
## Immutability
I know that lots of stdlib functions (like `map`, `sumOf`, etc.) use mutable state under the hood.
But that mutable stays in place meaning that I can implement such functions without
any mutability, so I still allowed to use them.
### Loops
You may ask how one will create loops which obviously use a concept
of a mutable variable and are obviously required to solve almost any task?
They will be emulated using tail-recursive functions like this:
```kotlin
fun loop(index: Int) {
println(index)
loop(index = index + 1)
}
```
This creates infinite loop without any mutability.
- But it will throw stackoverflow exception!!! – One may say
And they will be absolutely correct. It will throw exception unless we add
a special modifier called `tailrec` which optimizes tail recursion and
unwraps it back to loops after compilation. So:
```kotlin
tailrec fun loop(index: Int) {
println(index)
loop(index = index + 1)
}
```
This will not throw any exception and will infinitely print natural numbers.