What I learned by solving 50 Advent of Code challenges in Rust - RustNation UK 2023

👋I'm Luciano ( 🍕🍝 ) Senior Architect @ fourTheorem nodejsdp.link 📔Co-Author of Node.js Design Patterns 👉 Let's connect! (blog) (twitter) (twitch) (github) loige.co @loige loige lmammino Grab the slides 4

Always re-imagining We are a pioneering technology consultancy focused on AWS and serverless | | Accelerated Serverless AI as a Service Platform Modernisation loige ✉Reach out to us at 😇We are always looking for talent: hello@fourTheorem.com fth.link/careers 5

loige podcast awsbites.com How do you write Lambda Functions in Rust? 6

Why am I learning Rust 🦀 Full-stack Web Developer turning Cloud Architect loige Experience with dynamic scripting languages (JavaScript, Python, Php) Looked into Go for performance-sensitive applications Rust seemed like the natural next step ... and it's fun! 7

How it is going loige error[E0382]: borrow of moved value: `v` --> src/main.rs:6:19 | 4 | let v = vec![2, 3, 5, 7, 11, 13, 17]; | - move occurs because `v` has type `Vec<i32>`, whic 5 | hold_my_vec(v); | - value moved here 6 | let element = v.get(3); | ^^^^^^^^ value borrowed here after move | 1 2 3 4 5 6 7 8 9 10 #[stable(feature = "future_poll_fn", since = "1.64.0")] impl<T, F> Future for PollFn<F> where F: FnMut(&mut Context<'_>) -> Poll<T>, { type Output = T; fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> P // SAFETY: We are not moving out of the pinned field (unsafe { &mut self.get_unchecked_mut().f })(cx) } } 1 2 3 4 5 6 7 8 9 10 11 12 How it started 8

How it started -> How it is going loige 2019: Ported some JS code to Rust (resulted in ) jwtinfo 2020-2022: Live streamed solving Advent of Code in Rust + some other small side-projects and coding challenges Nothing "production ready" as of today 🤷 Excited about Serverless Rust on AWS 9

Yeah, but it's not really about tech... loige 10

It's about people loige @gbinside 12

🔥Hot take If you are struggling to learn Rust (or anything else, really)... Find a learning buddy! loige 14

Advent of Code . com loige github.com/lmammino/rust-advent 15

loige Valve NV has flow rate=5; tunnels lead to valves ZV, CG, YB, HX, OY Valve NU has flow rate=6; tunnels lead to valves DA, MA, OA, DK Valve VU has flow rate=0; tunnels lead to valves PS, FX Valve JW has flow rate=0; tunnels lead to valves AA, MD Valve RI has flow rate=0; tunnels lead to valves OY, DG Valve DG has flow rate=9; tunnels lead to valves TG, RI, DF, EV, KW Valve PH has flow rate=7; tunnels lead to valves KW, OW, LT, LZ Valve KZ has flow rate=12; tunnels lead to valves ET, QV, CK, MS Valve IX has flow rate=0; tunnels lead to valves TS, DO Valve MS has flow rate=0; tunnels lead to valves LZ, KZ Valve IL has flow rate=0; tunnels lead to valves DO, ET Valve EJ has flow rate=20; tunnels lead to valves AV, JY Valve DK has flow rate=0; tunnels lead to valves NU, CG Valve YB has flow rate=0; tunnels lead to valves NV, PS Valve OA has flow rate=0; tunnels lead to valves YA, NU Valve DA has flow rate=0; tunnels lead to valves NU, RG Valve KO has flow rate=0; tunnels lead to valves AA, TG Valve RG has flow rate=4; tunnels lead to valves DF, DA, ZV, MD, LB Valve MA has flow rate=0; tunnels lead to valves AA, NU Valve OW has flow rate=0; tunnels lead to valves DO, PH Valve KW has flow rate=0; tunnels lead to valves DG, PH Valve DO has flow rate=14; tunnels lead to valves IX, IL, CZ, OW Valve DF has flow rate=0; tunnels lead to valves RG, DG Valve TG has flow rate=0; tunnels lead to valves DG, KO Valve LB has flow rate=0; tunnels lead to valves RG, FX Valve HX has flow rate=0; tunnels lead to valves AA, NV Valve GB has flow rate=0; tunnels lead to valves AV, XK Valve CG has flow rate=0; tunnels lead to valves DK, NV Valve LT has flow rate=0; tunnels lead to valves AO, PH Valve FX has flow rate=23; tunnels lead to valves LB, HY, VU Valve ET has flow rate=0; tunnels lead to valves IL, KZ Valve CK has flow rate=0; tunnels lead to valves UX, KZ Valve LZ has flow rate=0; tunnels lead to valves PH, MS Valve YA has flow rate=17; tunnels lead to valves JY, OA Valve TS has flow rate=0; tunnels lead to valves NO, IX Valve NO has flow rate=8; tunnel leads to valve TS Valve XK has flow rate=24; tunnel leads to valve GB 1. Read & understand the puzzle 2. Parse the input 3. Write some code 4. Find solution 5. Submit your solution (unlocks part 2) 6. Repeat from point 1 for part 2 18

1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 y2022 - Day 1: Calorie Counting loige sum sum sum sum sum max 6000 4000 11000 24000 20 10000 24000

fn classic(input: &str) -> u64 { let mut max = 0; let batches = input.split("nn"); for batch in batches { let lines = batch.lines(); let mut total = 0; for line in lines { let value = line.parse::<u64>().unwrap(); total += value; } if total > max { max = total; } } max } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 let mut max = 0; max fn classic(input: &str) -> u64 { 1 2 let batches = input.split("nn"); 3 for batch in batches { 4 let lines = batch.lines(); 5 let mut total = 0; 6 for line in lines { 7 let value = line.parse::<u64>().unwrap(); 8 total += value; 9 } 10 if total > max { 11 max = total; 12 } 13 } 14 15 } 16 let batches = input.split("nn"); fn classic(input: &str) -> u64 { 1 let mut max = 0; 2 3 for batch in batches { 4 let lines = batch.lines(); 5 let mut total = 0; 6 for line in lines { 7 let value = line.parse::<u64>().unwrap(); 8 total += value; 9 } 10 if total > max { 11 max = total; 12 } 13 } 14 max 15 } 16 for batch in batches { } fn classic(input: &str) -> u64 { 1 let mut max = 0; 2 let batches = input.split("nn"); 3 4 let lines = batch.lines(); 5 let mut total = 0; 6 for line in lines { 7 let value = line.parse::<u64>().unwrap(); 8 total += value; 9 } 10 if total > max { 11 max = total; 12 } 13 14 max 15 } 16 let lines = batch.lines(); let mut total = 0; fn classic(input: &str) -> u64 { 1 let mut max = 0; 2 let batches = input.split("nn"); 3 for batch in batches { 4 5 6 for line in lines { 7 let value = line.parse::<u64>().unwrap(); 8 total += value; 9 } 10 if total > max { 11 max = total; 12 } 13 } 14 max 15 } 16 for line in lines { } fn classic(input: &str) -> u64 { 1 let mut max = 0; 2 let batches = input.split("nn"); 3 for batch in batches { 4 let lines = batch.lines(); 5 let mut total = 0; 6 7 let value = line.parse::<u64>().unwrap(); 8 total += value; 9 10 if total > max { 11 max = total; 12 } 13 } 14 max 15 } 16 let value = line.parse::<u64>().unwrap(); fn classic(input: &str) -> u64 { 1 let mut max = 0; 2 let batches = input.split("nn"); 3 for batch in batches { 4 let lines = batch.lines(); 5 let mut total = 0; 6 for line in lines { 7 8 total += value; 9 } 10 if total > max { 11 max = total; 12 } 13 } 14 max 15 } 16 total += value; fn classic(input: &str) -> u64 { 1 let mut max = 0; 2 let batches = input.split("nn"); 3 for batch in batches { 4 let lines = batch.lines(); 5 let mut total = 0; 6 for line in lines { 7 let value = line.parse::<u64>().unwrap(); 8 9 } 10 if total > max { 11 max = total; 12 } 13 } 14 max 15 } 16 if total > max { max = total; } fn classic(input: &str) -> u64 { 1 let mut max = 0; 2 let batches = input.split("nn"); 3 for batch in batches { 4 let lines = batch.lines(); 5 let mut total = 0; 6 for line in lines { 7 let value = line.parse::<u64>().unwrap(); 8 total += value; 9 } 10 11 12 13 } 14 max 15 } 16 fn classic(input: &str) -> u64 { let mut max = 0; let batches = input.split("nn"); for batch in batches { let lines = batch.lines(); let mut total = 0; for line in lines { let value = line.parse::<u64>().unwrap(); total += value; } if total > max { max = total; } } max } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Classic noob approach loige 21

fn combinators(input: &str) -> u64 { input .split("nn") .map(|batch| { batch .lines() .map(|line| line.parse::<u64>().unwrap()) .sum::<u64>() }) .max() .unwrap() } 1 2 3 4 5 6 7 8 9 10 11 12 input .split("nn") fn combinators(input: &str) -> u64 { 1 2 3 .map(|batch| { 4 batch 5 .lines() 6 .map(|line| line.parse::<u64>().unwrap()) 7 .sum::<u64>() 8 }) 9 .max() 10 .unwrap() 11 } 12 .map(|batch| { }) fn combinators(input: &str) -> u64 { 1 input 2 .split("nn") 3 4 batch 5 .lines() 6 .map(|line| line.parse::<u64>().unwrap()) 7 .sum::<u64>() 8 9 .max() 10 .unwrap() 11 } 12 batch .lines() .map(|line| line.parse::<u64>().unwrap()) .sum::<u64>() fn combinators(input: &str) -> u64 { 1 input 2 .split("nn") 3 .map(|batch| { 4 5 6 7 8 }) 9 .max() 10 .unwrap() 11 } 12 .max() .unwrap() fn combinators(input: &str) -> u64 { 1 input 2 .split("nn") 3 .map(|batch| { 4 batch 5 .lines() 6 .map(|line| line.parse::<u64>().unwrap()) 7 .sum::<u64>() 8 }) 9 10 11 } 12 fn combinators(input: &str) -> u64 { input .split("nn") .map(|batch| { batch .lines() .map(|line| line.parse::<u64>().unwrap()) .sum::<u64>() }) .max() .unwrap() } 1 2 3 4 5 6 7 8 9 10 11 12 Combinators approach loige 22

Nice, but the classic noob version must be much faster, right? 🤔 loige 23

Yeah, but I am sure that iterator combinators are not always flexible enough, right? 🤔 loige 25

1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 y2022 Day 1: Calorie Counting (part 2) loige sum sum sum sum sum top 3 6000 4000 11000 24000 26 10000 24000 11000 10000 sum 45000

fn combinators(input: &str) -> u64 { input .split("nn") .map(|batch| { batch .lines() .map(|line| line.parse::<u64>().unwrap()) .sum::<u64>() }) .sort_descending() .take(3) .sum() } 1 2 3 4 5 6 7 8 9 10 11 12 13 .sort_descending() fn combinators(input: &str) -> u64 { 1 input 2 .split("nn") 3 .map(|batch| { 4 batch 5 .lines() 6 .map(|line| line.parse::<u64>().unwrap()) 7 .sum::<u64>() 8 }) 9 10 .take(3) 11 .sum() 12 } 13 .take(3) fn combinators(input: &str) -> u64 { 1 input 2 .split("nn") 3 .map(|batch| { 4 batch 5 .lines() 6 .map(|line| line.parse::<u64>().unwrap()) 7 .sum::<u64>() 8 }) 9 .sort_descending() 10 11 .sum() 12 } 13 .sum() fn combinators(input: &str) -> u64 { 1 input 2 .split("nn") 3 .map(|batch| { 4 batch 5 .lines() 6 .map(|line| line.parse::<u64>().unwrap()) 7 .sum::<u64>() 8 }) 9 .sort_descending() 10 .take(3) 11 12 } 13 fn combinators(input: &str) -> u64 { input .split("nn") .map(|batch| { batch .lines() .map(|line| line.parse::<u64>().unwrap()) .sum::<u64>() }) .sort_descending() .take(3) .sum() } 1 2 3 4 5 6 7 8 9 10 11 12 13 loige 27

.sort_descending() fn combinators(input: &str) -> u64 { 1 input 2 .split("nn") 3 .map(|batch| { 4 batch 5 .lines() 6 .map(|line| line.parse::<u64>().unwrap()) 7 .sum::<u64>() 8 }) 9 10 .take(3) 11 .sum() 12 } 13 loige 🤷 28

But iterator combinators can be "extended" 🤫 loige $ cargo add itertools 29

use itertools::Itertools; fn combinators(input: &str) -> u64 { input .split("nn") .map(|batch| { batch .lines() .map(|line| line.parse::<u64>().unwrap()) .sum::<u64>() }) .sorted() .rev() .take(3) .sum() } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 use itertools::Itertools; 1 2 fn combinators(input: &str) -> u64 { 3 input 4 .split("nn") 5 .map(|batch| { 6 batch 7 .lines() 8 .map(|line| line.parse::<u64>().unwrap()) 9 .sum::<u64>() 10 }) 11 .sorted() 12 .rev() 13 .take(3) 14 .sum() 15 } 16 .sorted() .rev() use itertools::Itertools; 1 2 fn combinators(input: &str) -> u64 { 3 input 4 .split("nn") 5 .map(|batch| { 6 batch 7 .lines() 8 .map(|line| line.parse::<u64>().unwrap()) 9 .sum::<u64>() 10 }) 11 12 13 .take(3) 14 .sum() 15 } 16 use itertools::Itertools; fn combinators(input: &str) -> u64 { input .split("nn") .map(|batch| { batch .lines() .map(|line| line.parse::<u64>().unwrap()) .sum::<u64>() }) .sorted() .rev() .take(3) .sum() } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 loige 30

.sorted() use itertools::Itertools; 1 2 fn combinators(input: &str) -> u64 { 3 input 4 .split("nn") 5 .map(|batch| { 6 batch 7 .lines() 8 .map(|line| line.parse::<u64>().unwrap()) 9 .sum::<u64>() 10 }) 11 12 .rev() 13 .take(3) 14 .sum() 15 } 16 loige 🤩 added by itertools 31

But... Do we really want to sort? 😕 loige 32

💡IDEA: Consume the iterator and, as you go, keep the current top 3 in a vec... loige 33

💡IDEA: Consume the iterator and, as you go, keep the current top 3 in a vec... loige 100 22 44 1 120 top3 = [] 34

loige 100 22 44 1 120 top3 = [] 👉 💡IDEA: Consume the iterator and, as you go, keep the current top 3 in a vec... 35

loige 100 22 44 1 120 top3 = [100] 👉 💡IDEA: Consume the iterator and, as you go, keep the current top 3 in a vec... 36

loige 100 22 44 1 120 top3 = [100] 👉 💡IDEA: Consume the iterator and, as you go, keep the current top 3 in a vec... 37

loige 100 22 44 1 120 top3 = [100,22] 👉 💡IDEA: Consume the iterator and, as you go, keep the current top 3 in a vec... 38

loige 100 22 44 1 120 top3 = [100,22] 👉 💡IDEA: Consume the iterator and, as you go, keep the current top 3 in a vec... 39

loige 100 22 44 1 120 top3 = [100,44,22] 👉 💡IDEA: Consume the iterator and, as you go, keep the current top 3 in a vec... 40

loige 100 22 44 1 120 top3 = [120,100,44] This is O(n*m) vs sorting O(n*logn) ⚡ * indulge me and let's ignore we could have used radix sort here... ** O(n) for very small m, top100 would be expensive! 💡IDEA: Consume the iterator and, as you go, keep the current top 3 in a vec... 44

trait TopN { fn top_n(self, n: usize) -> Vec<u64>; } 1 2 3 loige That's what we want for now, but can it be more "generic"? 🧐 45

trait TopN<T> { fn top_n(self, n: usize) -> Vec<T>; } 1 2 3 loige Makes the trait "generic" over any type T T is used as part of the return type of the function 46

That's a cool trait indeed... but I am sure we cannot implement it for "all" iterators, right?! 🤷 loige 47

Of course, we can! 💪 loige It's called a "blanket implementation". 48

impl<T, U: Iterator<Item = T>> TopN<T> for U { fn top_n(self, n: usize) -> Vec<T> { } } 1 2 // TODO: 3 unimplemented!(); 4 5 6 loige All types U that implements the Iterator trait producing Items of type T We implement TopN<T> for all types U (iterators producing T)! 49

impl<T, U: Iterator<Item = T>> TopN<T> for U { fn top_n(self, n: usize) -> Vec<T> { let mut top = Vec::with_capacity(n); for value in self { for i in 0..n { if let Some(top_value) = top.get(i) { if value > *top_value { top[i..].rotate_right(1); top[i] = value; break; } } else { top.push(value); break; } } } top } } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 let mut top = Vec::with_capacity(n); impl<T, U: Iterator<Item = T>> TopN<T> for U { 1 fn top_n(self, n: usize) -> Vec<T> { 2 3 for value in self { 4 for i in 0..n { 5 if let Some(top_value) = top.get(i) { 6 if value > *top_value { 7 top[i..].rotate_right(1); 8 top[i] = value; 9 break; 10 } 11 } else { 12 top.push(value); 13 break; 14 } 15 } 16 } 17 top 18 } 19 } 20 if value > *top_value { impl<T, U: Iterator<Item = T>> TopN<T> for U { 1 fn top_n(self, n: usize) -> Vec<T> { 2 let mut top = Vec::with_capacity(n); 3 for value in self { 4 for i in 0..n { 5 if let Some(top_value) = top.get(i) { 6 7 top[i..].rotate_right(1); 8 top[i] = value; 9 break; 10 } 11 } else { 12 top.push(value); 13 break; 14 } 15 } 16 } 17 top 18 } 19 } 20 loige 50

if value > *top_value { impl<T, U: Iterator<Item = T>> TopN<T> for U { 1 fn top_n(self, n: usize) -> Vec<T> { 2 let mut top = Vec::with_capacity(n); 3 for value in self { 4 for i in 0..n { 5 if let Some(top_value) = top.get(i) { 6 7 top[i..].rotate_right(1); 8 top[i] = value; 9 break; 10 } 11 } else { 12 top.push(value); 13 break; 14 } 15 } 16 } 17 top 18 } 19 } 20 loige 51

impl<T: PartialOrd, U: Iterator<Item = T>> TopN<T> for U { 1 fn top_n(self, n: usize) -> Vec<T> { 2 let mut top = Vec::with_capacity(n); 3 for value in self { 4 for i in 0..n { 5 if let Some(top_value) = top.get(i) { 6 if value > *top_value { 7 top[i..].rotate_right(1); 8 top[i] = value; 9 break; 10 } 11 } else { 12 top.push(value); 13 break; 14 } 15 } 16 } 17 top 18 } 19 } 20 loige Restricting T only to types that can be compared! 👍 52

fn combinators_no_sort(input: &str) -> u64 { input .split("nn") .map(|batch| { batch .lines() .map(|line| line.parse::<u64>().unwrap()) .sum::<u64>() }) .top_n(3) .iter() .sum() } 1 2 3 4 5 6 7 8 9 10 11 12 13 .top_n(3) .iter() .sum() fn combinators_no_sort(input: &str) -> u64 { 1 input 2 .split("nn") 3 .map(|batch| { 4 batch 5 .lines() 6 .map(|line| line.parse::<u64>().unwrap()) 7 .sum::<u64>() 8 }) 9 10 11 12 } 13 loige 53

.top_n(3) fn combinators_no_sort(input: &str) -> u64 { 1 input 2 .split("nn") 3 .map(|batch| { 4 batch 5 .lines() 6 .map(|line| line.parse::<u64>().unwrap()) 7 .sum::<u64>() 8 }) 9 10 .iter() 11 .sum() 12 } 13 loige 😍 OMG, we added this! 54

OK, but you used a Vec there... I heard rustaceans don't like unnecessary allocations, right?! 🤷 loige 55

trait Top<T> { fn top(self, n: usize) -> Vec<T>; } impl<T: PartialOrd, U: Iterator<Item = T>> Top<T> for U { fn top(self, n: usize) -> Vec<T> { let mut top = Vec::with_capacity(n); // ... top } } 1 2 3 4 5 6 7 8 9 10 11 loige We want to replace these with an array... 56

trait Top<T> { fn top(self, n: usize) -> [T;n]; } impl<T: PartialOrd, U: Iterator<Item = T>> Top<T> for U { fn top(self, n: usize) -> [T;n] { let mut top = [T;n]; // ... top } } 1 2 3 4 5 6 7 8 9 10 11 fn top(self, n: usize) -> [T;n]; trait Top<T> { 1 2 } 3 4 impl<T: PartialOrd, U: Iterator<Item = T>> Top<T> for U { 5 fn top(self, n: usize) -> [T;n] { 6 let mut top = [T;n]; 7 // ... 8 top 9 } 10 } 11 loige 57

fn top<const N: usize>(self) -> [T; N]; trait Top<T> { 1 2 } 3 4 impl<T: PartialOrd, U: Iterator<Item = T>> Top<T> for U { 5 fn top<const N: usize>(self) -> [T; N] { 6 let mut top = [T;N]; 7 // ... 8 top 9 } 10 } 11 loige const generics syntax 58

let mut top = [T;N]; trait Top<T> { 1 fn top<const N: usize>(self) -> [T; N]; 2 } 3 4 impl<T: PartialOrd, U: Iterator<Item = T>> Top<T> for U { 5 fn top<const N: usize>(self) -> [T; N] { 6 7 // ... 8 top 9 } 10 } 11 loige 59

let mut top = [Default::default(); N]; trait Top<T> { 1 fn top<const N: usize>(self) -> [T; N]; 2 } 3 4 impl<T: PartialOrd, U: Iterator<Item = T>> Top<T> for U { 5 fn top<const N: usize>(self) -> [T; N] { 6 7 // ... 8 top 9 } 10 } 11 loige 60

impl<T: Default + Copy + PartialOrd, U: Iterator<Item = T>> Top<T> for let mut top = [Default::default(); N]; trait Top<T> { 1 fn top<const N: usize>(self) -> [T; N]; 2 } 3 4 5 fn top<const N: usize>(self) -> [T; N] { 6 7 // ... 8 top 9 } 10 } 11 loige 61

impl<T: Default + Copy + PartialOrd, U: Iterator<Item = T>> Top<T> for let mut top = [Default::default(); N]; trait Top<T> { 1 fn top<const N: usize>(self) -> [T; N]; 2 } 3 4 5 fn top<const N: usize>(self) -> [T; N] { 6 7 // ... 8 top 9 } 10 } 11 loige Do we really need this? 62

impl<T: Default + PartialOrd, U: Iterator<Item = T>> Top<T> for U { let mut top = core::array::from_fn(|_| Default::default()); trait Top<T> { 1 fn top<const N: usize>(self) -> [T; N]; 2 } 3 4 5 fn top<const N: usize>(self) -> [T; N] { 6 7 // ... 8 top 9 } 10 } 11 loige Allows us to avoid Copy 63

impl<T: Default + PartialOrd, U: Iterator<Item = T>> Top<T> for U { let mut top = core::array::from_fn(|_| Default::default()); trait Top<T> { 1 fn top<const N: usize>(self) -> [T; N]; 2 } 3 4 5 fn top<const N: usize>(self) -> [T; N] { 6 7 // ... 8 top 9 } 10 } 11 loige Note: This works for now, but it's not a perfect solution 😥 (e.g. what if there are fewer than N items?) 64

fn combinators_no_sort_const(input: &str) -> u64 { input .split("nn") .map(|batch| { batch .lines() .map(|line| line.parse::<u64>().unwrap()) .sum::<u64>() }) .top::<3>() .iter() .sum() } 1 2 3 4 5 6 7 8 9 10 11 12 13 .top::<3>() fn combinators_no_sort_const(input: &str) -> u64 { 1 input 2 .split("nn") 3 .map(|batch| { 4 batch 5 .lines() 6 .map(|line| line.parse::<u64>().unwrap()) 7 .sum::<u64>() 8 }) 9 10 .iter() 11 .sum() 12 } 13 loige 65

.top::<3>() fn combinators_no_sort_const(input: &str) -> u64 { 1 input 2 .split("nn") 3 .map(|batch| { 4 batch 5 .lines() 6 .map(|line| line.parse::<u64>().unwrap()) 7 .sum::<u64>() 8 }) 9 10 .iter() 11 .sum() 12 } 13 loige Slightly different syntax 🐟 Phew... we did it! 😮💨 66

Which one do you think is faster? 🧐 loige Itertools no_sort_vec no_sort_array 1. 2. 3. 67

Which one do you think is faster? 🧐 loige Itertools no_sort_vec no_sort_array 1. 2. 3. 37.517 µs 33.284 µs 32.957 µs BTW, is awesome! cargo bench ⭐ 68

But let's talk more about const generics, what else can you do with them? loige 69

struct Point<const D: usize>([i32; D]); fn make_2d_point(x: i32, y: i32) -> Point<2> { Point([x, y]) } fn make_3d_point(x: i32, y: i32, z: i32) -> Point<3> { Point([x, y, z]) } fn make_4d_point(x: i32, y: i32, z: i32, w: i32) -> Point<4> { Point([x, y, z, w]) } 1 2 3 4 5 6 7 8 9 10 11 12 13 struct Point<const D: usize>([i32; D]); 1 2 fn make_2d_point(x: i32, y: i32) -> Point<2> { 3 Point([x, y]) 4 } 5 6 fn make_3d_point(x: i32, y: i32, z: i32) -> Point<3> { 7 Point([x, y, z]) 8 } 9 10 fn make_4d_point(x: i32, y: i32, z: i32, w: i32) -> Point<4> { 11 Point([x, y, z, w]) 12 } 13 struct Point<const D: usize>([i32; D]); fn make_2d_point(x: i32, y: i32) -> Point<2> { Point([x, y]) } 1 2 3 4 5 6 fn make_3d_point(x: i32, y: i32, z: i32) -> Point<3> { 7 Point([x, y, z]) 8 } 9 10 fn make_4d_point(x: i32, y: i32, z: i32, w: i32) -> Point<4> { 11 Point([x, y, z, w]) 12 } 13 struct Point<const D: usize>([i32; D]); fn make_3d_point(x: i32, y: i32, z: i32) -> Point<3> { Point([x, y, z]) } 1 2 fn make_2d_point(x: i32, y: i32) -> Point<2> { 3 Point([x, y]) 4 } 5 6 7 8 9 10 fn make_4d_point(x: i32, y: i32, z: i32, w: i32) -> Point<4> { 11 Point([x, y, z, w]) 12 } 13 struct Point<const D: usize>([i32; D]); fn make_4d_point(x: i32, y: i32, z: i32, w: i32) -> Point<4> { Point([x, y, z, w]) } 1 2 fn make_2d_point(x: i32, y: i32) -> Point<2> { 3 Point([x, y]) 4 } 5 6 fn make_3d_point(x: i32, y: i32, z: i32) -> Point<3> { 7 Point([x, y, z]) 8 } 9 10 11 12 13 struct Point<const D: usize>([i32; D]); fn make_2d_point(x: i32, y: i32) -> Point<2> { Point([x, y]) } fn make_3d_point(x: i32, y: i32, z: i32) -> Point<3> { Point([x, y, z]) } fn make_4d_point(x: i32, y: i32, z: i32, w: i32) -> Point<4> { Point([x, y, z, w]) } 1 2 3 4 5 6 7 8 9 10 11 12 13 y2020 - Day 17: Conway Cubes loige 70

let p5d = Point([1, 2, 3, 4, 5]); fn some_func() { 1 // ... 2 3 // ... 4 } 5 y2020 - Day 17: Conway Cubes loige No need to specify the type, Rust will infer Point<5> based on the length of the passed array! 71

v...>>.vv> .vv>>.vv.. >>.>v>...v >>v>>.>.v. v>v.vv.v.. >.>>..v... .vv..>.>v. v.v..>>v.v ....v..v.> y2021 - Day 25: Sea Cucumber loige Sometimes you have to handle grids of variable sizes. README example (10x9) 72

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.>>..v.>v..>>>v.v.v>>...>>v...v>....>.v>>...v.>.v.>...v>>vv.vvv>v....v>.v.>v......v.v.>>.>v...v...>vv.v.....>...>.>..vv.v..>..>.v>..>.v>.vv >..>.>.>>.v.v.>.v.vvv....>.v>v.v..v.v...>...vv..>>.>..>>>...v>.>.v..v.>>.......v.....>.v>vv.>.v..vv>>>>>>v...vvv..vvv>>>.v.>.v..v.v>v>v>..> v..>.v.vv>>vvvvv.....v>>v...vv....v>.>>v.v.>.>>v.vv....vv..v.>>.v.v.>v>....>....v.v>>>.>v.v.>v>v.v.v..>.>v>v......v.v>...>v.vvv...v>...vv.. >>vv.....v...v......>v.v..v>..v.v>..>>>.>>..>v>.v>>>.>v..>>>>v.>..vvvv.v>...v..vv.>.>v....>v.>>.....v>v....v..>.>.v>v.>.>.>v.v..>v......... y2021 - Day 25: Sea Cucumber loige Sometimes you have to handle grids of variable sizes. Actual input (139x137) 73

struct Grid<const W: usize, const H: usize> { cells: [[Option<Cell>; W]; H], } 1 2 3 y2021 - Day 25: Sea Cucumber loige You can use const generics to define a matrix with configurable dimensions 74

struct Grid<const W: usize, const H: usize> { cells: [[Option<Cell>; W]; H], } pub fn test_readme(input: &str) -> usize { let mut grid1: Grid<10, 9> = input.parse().unwrap(); // ... } pub fn part1(input: &str) -> usize { let mut grid1: Grid<139, 137> = input.parse().unwrap(); // ... } 1 2 3 4 5 6 7 8 9 10 11 12 13 pub fn test_readme(input: &str) -> usize { let mut grid1: Grid<10, 9> = input.parse().unwrap(); // ... struct Grid<const W: usize, const H: usize> { 1 cells: [[Option<Cell>; W]; H], 2 } 3 4 5 6 7 } 8 9 pub fn part1(input: &str) -> usize { 10 let mut grid1: Grid<139, 137> = input.parse().unwrap(); 11 // ... 12 } 13 pub fn part1(input: &str) -> usize { let mut grid1: Grid<139, 137> = input.parse().unwrap(); // ... } struct Grid<const W: usize, const H: usize> { 1 cells: [[Option<Cell>; W]; H], 2 } 3 4 pub fn test_readme(input: &str) -> usize { 5 let mut grid1: Grid<10, 9> = input.parse().unwrap(); 6 // ... 7 } 8 9 10 11 12 13 struct Grid<const W: usize, const H: usize> { cells: [[Option<Cell>; W]; H], } pub fn test_readme(input: &str) -> usize { let mut grid1: Grid<10, 9> = input.parse().unwrap(); // ... } pub fn part1(input: &str) -> usize { let mut grid1: Grid<139, 137> = input.parse().unwrap(); // ... } 1 2 3 4 5 6 7 8 9 10 11 12 13 y2021 - Day 25: Sea Cucumber loige 75

Parsing (Ergo, extracting data from text) loige 76

mask = 000000000000000000000000000000X1001X mem[42] = 100 mask = 00000000000000000000000000000000X0XX mem[26] = 1 ... y2020 - Day 14: Docking Data loige enum Instr { Mask(String), Mem(u64, u64), } 77

use std::str::FromStr; impl FromStr for Instr { type Err = String; fn from_str(s: &str) -> Result<Self, Self::Err> { if s.starts_with("mask") { Ok(Instr::Mask(s[7..].to_string())) } else if s.starts_with("mem") { let addr_value = &mut s[4..].split("] = "); let addr: u64 = addr_value.next().unwrap().parse().unwrap(); let value: u64 = addr_value.next().unwrap().parse().unwrap(); Ok(Instr::Mem(addr, value)) } else { Err(format!("Invalid line found: {s}")) } } } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 use std::str::FromStr; impl FromStr for Instr { } 1 2 3 type Err = String; 4 5 fn from_str(s: &str) -> Result<Self, Self::Err> { 6 if s.starts_with("mask") { 7 Ok(Instr::Mask(s[7..].to_string())) 8 } else if s.starts_with("mem") { 9 let addr_value = &mut s[4..].split("] = "); 10 let addr: u64 = addr_value.next().unwrap().parse().unwrap(); 11 let value: u64 = addr_value.next().unwrap().parse().unwrap(); 12 Ok(Instr::Mem(addr, value)) 13 } else { 14 Err(format!("Invalid line found: {s}")) 15 } 16 } 17 18 use std::str::FromStr; impl FromStr for Instr { type Err = String; fn from_str(s: &str) -> Result<Self, Self::Err> { } } 1 2 3 4 5 6 if s.starts_with("mask") { 7 Ok(Instr::Mask(s[7..].to_string())) 8 } else if s.starts_with("mem") { 9 let addr_value = &mut s[4..].split("] = "); 10 let addr: u64 = addr_value.next().unwrap().parse().unwrap(); 11 let value: u64 = addr_value.next().unwrap().parse().unwrap(); 12 Ok(Instr::Mem(addr, value)) 13 } else { 14 Err(format!("Invalid line found: {s}")) 15 } 16 17 18 if s.starts_with("mask") { Ok(Instr::Mask(s[7..].to_string())) use std::str::FromStr; 1 2 impl FromStr for Instr { 3 type Err = String; 4 5 fn from_str(s: &str) -> Result<Self, Self::Err> { 6 7 8 } else if s.starts_with("mem") { 9 let addr_value = &mut s[4..].split("] = "); 10 let addr: u64 = addr_value.next().unwrap().parse().unwrap(); 11 let value: u64 = addr_value.next().unwrap().parse().unwrap(); 12 Ok(Instr::Mem(addr, value)) 13 } else { 14 Err(format!("Invalid line found: {s}")) 15 } 16 } 17 } 18 } else if s.starts_with("mem") { Ok(Instr::Mem(addr, value)) use std::str::FromStr; 1 2 impl FromStr for Instr { 3 type Err = String; 4 5 fn from_str(s: &str) -> Result<Self, Self::Err> { 6 if s.starts_with("mask") { 7 Ok(Instr::Mask(s[7..].to_string())) 8 9 let addr_value = &mut s[4..].split("] = "); 10 let addr: u64 = addr_value.next().unwrap().parse().unwrap(); 11 let value: u64 = addr_value.next().unwrap().parse().unwrap(); 12 13 } else { 14 Err(format!("Invalid line found: {s}")) 15 } 16 } 17 } 18 } else { Err(format!("Invalid line found: {s}")) } use std::str::FromStr; 1 2 impl FromStr for Instr { 3 type Err = String; 4 5 fn from_str(s: &str) -> Result<Self, Self::Err> { 6 if s.starts_with("mask") { 7 Ok(Instr::Mask(s[7..].to_string())) 8 } else if s.starts_with("mem") { 9 let addr_value = &mut s[4..].split("] = "); 10 let addr: u64 = addr_value.next().unwrap().parse().unwrap(); 11 let value: u64 = addr_value.next().unwrap().parse().unwrap(); 12 Ok(Instr::Mem(addr, value)) 13 14 15 16 } 17 } 18 use std::str::FromStr; impl FromStr for Instr { type Err = String; fn from_str(s: &str) -> Result<Self, Self::Err> { if s.starts_with("mask") { Ok(Instr::Mask(s[7..].to_string())) } else if s.starts_with("mem") { let addr_value = &mut s[4..].split("] = "); let addr: u64 = addr_value.next().unwrap().parse().unwrap(); let value: u64 = addr_value.next().unwrap().parse().unwrap(); Ok(Instr::Mem(addr, value)) } else { Err(format!("Invalid line found: {s}")) } } } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 loige 78

let mask: Instr = "mask = 00000000000000X1001X".parse().unwrap(); assert_eq!(mask, Instr::Mask("00000000000000X1001X".to_string())); let mem: Instr = "mem[42] = 100".parse().unwrap(); assert_eq!(mem, Instr::Mem(42, 100)); 1 2 3 4 5 let mask: Instr = "mask = 00000000000000X1001X".parse().unwrap(); assert_eq!(mask, Instr::Mask("00000000000000X1001X".to_string())); 1 2 3 let mem: Instr = "mem[42] = 100".parse().unwrap(); 4 assert_eq!(mem, Instr::Mem(42, 100)); 5 let mem: Instr = "mem[42] = 100".parse().unwrap(); assert_eq!(mem, Instr::Mem(42, 100)); let mask: Instr = "mask = 00000000000000X1001X".parse().unwrap(); 1 assert_eq!(mask, Instr::Mask("00000000000000X1001X".to_string())); 2 3 4 5 let mask: Instr = "mask = 00000000000000X1001X".parse().unwrap(); assert_eq!(mask, Instr::Mask("00000000000000X1001X".to_string())); let mem: Instr = "mem[42] = 100".parse().unwrap(); assert_eq!(mem, Instr::Mem(42, 100)); 1 2 3 4 5 loige 79

let mask: Instr = "mask = 00000000000000X1001X".parse().unwrap(); let mem: Instr = "mem[42] = 100".parse().unwrap(); 1 assert_eq!(mask, Instr::Mask("00000000000000X1001X".to_string())); 2 3 4 assert_eq!(mem, Instr::Mem(42, 100)); 5 loige Implementing the FromStr trait, will make the parse() method available! 80

oops, I did it again: unnecessary allocations! 🤷 loige Why don't you just take a slice from the input rather than allocating a String? 81

enum Instr<'a> { Mask(&'a str), Mem(u64, u64), } impl<'a> FromStr for Instr<'a> { type Err = String; fn from_str(s: &'a str) -> Result<Self, Self::Err> { if s.starts_with("mask") { Ok(Instr::Mask(&s[7..])) } else if s.starts_with("mem") { let addr_value = &mut s[4..].split("] = "); let addr: u64 = addr_value.next().unwrap().parse().unwrap(); let value: u64 = addr_value.next().unwrap().parse().unwrap(); Ok(Instr::Mem(addr, value)) } else { Err(format!("Invalid line found: {s}")) } } } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 enum Instr<'a> { Mask(&'a str), } 1 2 Mem(u64, u64), 3 4 5 6 impl<'a> FromStr for Instr<'a> { 7 type Err = String; 8 9 fn from_str(s: &'a str) -> Result<Self, Self::Err> { 10 if s.starts_with("mask") { 11 Ok(Instr::Mask(&s[7..])) 12 } else if s.starts_with("mem") { 13 let addr_value = &mut s[4..].split("] = "); 14 let addr: u64 = addr_value.next().unwrap().parse().unwrap(); 15 let value: u64 = addr_value.next().unwrap().parse().unwrap(); 16 Ok(Instr::Mem(addr, value)) 17 } else { 18 Err(format!("Invalid line found: {s}")) 19 } 20 } 21 } 22 impl<'a> FromStr for Instr<'a> { enum Instr<'a> { 1 Mask(&'a str), 2 Mem(u64, u64), 3 } 4 5 6 7 type Err = String; 8 9 fn from_str(s: &'a str) -> Result<Self, Self::Err> { 10 if s.starts_with("mask") { 11 Ok(Instr::Mask(&s[7..])) 12 } else if s.starts_with("mem") { 13 let addr_value = &mut s[4..].split("] = "); 14 let addr: u64 = addr_value.next().unwrap().parse().unwrap(); 15 let value: u64 = addr_value.next().unwrap().parse().unwrap(); 16 Ok(Instr::Mem(addr, value)) 17 } else { 18 Err(format!("Invalid line found: {s}")) 19 } 20 } 21 } 22 fn from_str(s: &'a str) -> Result<Self, Self::Err> { enum Instr<'a> { 1 Mask(&'a str), 2 Mem(u64, u64), 3 } 4 5 6 impl<'a> FromStr for Instr<'a> { 7 type Err = String; 8 9 10 if s.starts_with("mask") { 11 Ok(Instr::Mask(&s[7..])) 12 } else if s.starts_with("mem") { 13 let addr_value = &mut s[4..].split("] = "); 14 let addr: u64 = addr_value.next().unwrap().parse().unwrap(); 15 let value: u64 = addr_value.next().unwrap().parse().unwrap(); 16 Ok(Instr::Mem(addr, value)) 17 } else { 18 Err(format!("Invalid line found: {s}")) 19 } 20 } 21 } 22 loige 82

fn from_str(s: &'a str) -> Result<Self, Self::Err> { enum Instr<'a> { 1 Mask(&'a str), 2 Mem(u64, u64), 3 } 4 5 6 impl<'a> FromStr for Instr<'a> { 7 type Err = String; 8 9 10 if s.starts_with("mask") { 11 Ok(Instr::Mask(&s[7..])) 12 } else if s.starts_with("mem") { 13 let addr_value = &mut s[4..].split("] = "); 14 let addr: u64 = addr_value.next().unwrap().parse().unwrap(); 15 let value: u64 = addr_value.next().unwrap().parse().unwrap(); 16 Ok(Instr::Mem(addr, value)) 17 } else { 18 Err(format!("Invalid line found: {s}")) 19 } 20 } 21 } 22 loige users.rust-lang.org/t/fromstr-and-lifetimes/12198 83

enum Instr<'a> { Mask(&'a str), Mem(u64, u64), } impl<'a> From<&'a str> for Instr<'a> { fn from(s: &'a str) -> Self { if s.starts_with("mask") { Instr::Mask(&s[7..]) } else if s.starts_with("mem") { let addr_value = &mut s[4..].split("] = "); let addr: u64 = addr_value.next().unwrap().parse().unwrap(); let value: u64 = addr_value.next().unwrap().parse().unwrap(); Instr::Mem(addr, value) } else { panic!("Invalid line found: {s}") } } } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 impl<'a> From<&'a str> for Instr<'a> { } enum Instr<'a> { 1 Mask(&'a str), 2 Mem(u64, u64), 3 } 4 5 6 7 fn from(s: &'a str) -> Self { 8 if s.starts_with("mask") { 9 Instr::Mask(&s[7..]) 10 } else if s.starts_with("mem") { 11 let addr_value = &mut s[4..].split("] = "); 12 let addr: u64 = addr_value.next().unwrap().parse().unwrap(); 13 let value: u64 = addr_value.next().unwrap().parse().unwrap(); 14 Instr::Mem(addr, value) 15 } else { 16 panic!("Invalid line found: {s}") 17 } 18 } 19 20 fn from(s: &'a str) -> Self { } enum Instr<'a> { 1 Mask(&'a str), 2 Mem(u64, u64), 3 } 4 5 6 impl<'a> From<&'a str> for Instr<'a> { 7 8 if s.starts_with("mask") { 9 Instr::Mask(&s[7..]) 10 } else if s.starts_with("mem") { 11 let addr_value = &mut s[4..].split("] = "); 12 let addr: u64 = addr_value.next().unwrap().parse().unwrap(); 13 let value: u64 = addr_value.next().unwrap().parse().unwrap(); 14 Instr::Mem(addr, value) 15 } else { 16 panic!("Invalid line found: {s}") 17 } 18 19 } 20 panic!("Invalid line found: {s}") enum Instr<'a> { 1 Mask(&'a str), 2 Mem(u64, u64), 3 } 4 5 6 impl<'a> From<&'a str> for Instr<'a> { 7 fn from(s: &'a str) -> Self { 8 if s.starts_with("mask") { 9 Instr::Mask(&s[7..]) 10 } else if s.starts_with("mem") { 11 let addr_value = &mut s[4..].split("] = "); 12 let addr: u64 = addr_value.next().unwrap().parse().unwrap(); 13 let value: u64 = addr_value.next().unwrap().parse().unwrap(); 14 Instr::Mem(addr, value) 15 } else { 16 17 } 18 } 19 } 20 loige 84

panic!("Invalid line found: {s}") enum Instr<'a> { 1 Mask(&'a str), 2 Mem(u64, u64), 3 } 4 5 6 impl<'a> From<&'a str> for Instr<'a> { 7 fn from(s: &'a str) -> Self { 8 if s.starts_with("mask") { 9 Instr::Mask(&s[7..]) 10 } else if s.starts_with("mem") { 11 let addr_value = &mut s[4..].split("] = "); 12 let addr: u64 = addr_value.next().unwrap().parse().unwrap(); 13 let value: u64 = addr_value.next().unwrap().parse().unwrap(); 14 Instr::Mem(addr, value) 15 } else { 16 17 } 18 } 19 } 20 loige This panic gives me anxiety 😰 85

use std::convert::{TryFrom, TryInto}; enum Instr<'a> { Mask(&'a str), Mem(u64, u64), } impl<'a> TryFrom<&'a str> for Instr<'a> { type Error = String; fn try_from(s: &'a str) -> Result<Self, Self::Error> { if s.starts_with("mask") { Ok(Instr::Mask(&s[7..])) } else if s.starts_with("mem") { let addr_value = &mut s[4..].split("] = "); let addr: u64 = addr_value.next().unwrap().parse().unwrap(); let value: u64 = addr_value.next().unwrap().parse().unwrap(); Ok(Instr::Mem(addr, value)) } else { Err(format!("Invalid line found: {s}")) } } } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 use std::convert::{TryFrom, TryInto}; 1 2 enum Instr<'a> { 3 Mask(&'a str), 4 Mem(u64, u64), 5 } 6 7 impl<'a> TryFrom<&'a str> for Instr<'a> { 8 type Error = String; 9 10 fn try_from(s: &'a str) -> Result<Self, Self::Error> { 11 if s.starts_with("mask") { 12 Ok(Instr::Mask(&s[7..])) 13 } else if s.starts_with("mem") { 14 let addr_value = &mut s[4..].split("] = "); 15 let addr: u64 = addr_value.next().unwrap().parse().unwrap(); 16 let value: u64 = addr_value.next().unwrap().parse().unwrap(); 17 Ok(Instr::Mem(addr, value)) 18 } else { 19 Err(format!("Invalid line found: {s}")) 20 } 21 } 22 } 23 impl<'a> TryFrom<&'a str> for Instr<'a> { } use std::convert::{TryFrom, TryInto}; 1 2 enum Instr<'a> { 3 Mask(&'a str), 4 Mem(u64, u64), 5 } 6 7 8 type Error = String; 9 10 fn try_from(s: &'a str) -> Result<Self, Self::Error> { 11 if s.starts_with("mask") { 12 Ok(Instr::Mask(&s[7..])) 13 } else if s.starts_with("mem") { 14 let addr_value = &mut s[4..].split("] = "); 15 let addr: u64 = addr_value.next().unwrap().parse().unwrap(); 16 let value: u64 = addr_value.next().unwrap().parse().unwrap(); 17 Ok(Instr::Mem(addr, value)) 18 } else { 19 Err(format!("Invalid line found: {s}")) 20 } 21 } 22 23 type Error = String; use std::convert::{TryFrom, TryInto}; 1 2 enum Instr<'a> { 3 Mask(&'a str), 4 Mem(u64, u64), 5 } 6 7 impl<'a> TryFrom<&'a str> for Instr<'a> { 8 9 10 fn try_from(s: &'a str) -> Result<Self, Self::Error> { 11 if s.starts_with("mask") { 12 Ok(Instr::Mask(&s[7..])) 13 } else if s.starts_with("mem") { 14 let addr_value = &mut s[4..].split("] = "); 15 let addr: u64 = addr_value.next().unwrap().parse().unwrap(); 16 let value: u64 = addr_value.next().unwrap().parse().unwrap(); 17 Ok(Instr::Mem(addr, value)) 18 } else { 19 Err(format!("Invalid line found: {s}")) 20 } 21 } 22 } 23 fn try_from(s: &'a str) -> Result<Self, Self::Error> { } use std::convert::{TryFrom, TryInto}; 1 2 enum Instr<'a> { 3 Mask(&'a str), 4 Mem(u64, u64), 5 } 6 7 impl<'a> TryFrom<&'a str> for Instr<'a> { 8 type Error = String; 9 10 11 if s.starts_with("mask") { 12 Ok(Instr::Mask(&s[7..])) 13 } else if s.starts_with("mem") { 14 let addr_value = &mut s[4..].split("] = "); 15 let addr: u64 = addr_value.next().unwrap().parse().unwrap(); 16 let value: u64 = addr_value.next().unwrap().parse().unwrap(); 17 Ok(Instr::Mem(addr, value)) 18 } else { 19 Err(format!("Invalid line found: {s}")) 20 } 21 22 } 23 Ok(Instr::Mask(&s[7..])) Ok(Instr::Mem(addr, value)) Err(format!("Invalid line found: {s}")) use std::convert::{TryFrom, TryInto}; 1 2 enum Instr<'a> { 3 Mask(&'a str), 4 Mem(u64, u64), 5 } 6 7 impl<'a> TryFrom<&'a str> for Instr<'a> { 8 type Error = String; 9 10 fn try_from(s: &'a str) -> Result<Self, Self::Error> { 11 if s.starts_with("mask") { 12 13 } else if s.starts_with("mem") { 14 let addr_value = &mut s[4..].split("] = "); 15 let addr: u64 = addr_value.next().unwrap().parse().unwrap(); 16 let value: u64 = addr_value.next().unwrap().parse().unwrap(); 17 18 } else { 19 20 } 21 } 22 } 23 use std::convert::{TryFrom, TryInto}; enum Instr<'a> { Mask(&'a str), Mem(u64, u64), } impl<'a> TryFrom<&'a str> for Instr<'a> { type Error = String; fn try_from(s: &'a str) -> Result<Self, Self::Error> { if s.starts_with("mask") { Ok(Instr::Mask(&s[7..])) } else if s.starts_with("mem") { let addr_value = &mut s[4..].split("] = "); let addr: u64 = addr_value.next().unwrap().parse().unwrap(); let value: u64 = addr_value.next().unwrap().parse().unwrap(); Ok(Instr::Mem(addr, value)) } else { Err(format!("Invalid line found: {s}")) } } } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 loige 86

let mask: Instr = "mask = 00000000000000X1001X".try_into().unwrap(); let mem: Instr = "mem[42] = 100".try_into().unwrap(); 1 assert_eq!(mask, Instr::Mask("00000000000000X1001X")); 2 3 4 assert_eq!(mem, Instr::Mem(42, 100)); 5 loige Implementing the TryFrom trait, will make the try_into() method available! 87

Sensor at x=2, y=18: closest beacon is at x=-2, y=15 Sensor at x=9, y=16: closest beacon is at x=10, y=16 Sensor at x=13, y=2: closest beacon is at x=15, y=3 Sensor at x=12, y=14: closest beacon is at x=10, y=16 ... y2022 - Day 15: Beacon Exclusion Zone loige struct Pos { x: i64, y: i64, } let sensor = Pos { x: 13, y: 2, } let beacon = Pos { x: 15, y: 3, } 88

use regex::Regex; fn parse_line_regex(line: &str) -> (Pos, Pos) { let re = Regex::new( r"Sensor at x=(?P<x1>[-]?d+), y=(?P<y1>[-]?d+): closest beacon ) .unwrap(); let captures = re.captures(line).unwrap(); let sensor = Pos { x: captures["x1"].parse().unwrap(), y: captures["y1"].parse().unwrap(), }; let beacon = Pos { x: captures["x2"].parse().unwrap(), y: captures["y2"].parse().unwrap(), }; (sensor, beacon) } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 use regex::Regex; 1 2 fn parse_line_regex(line: &str) -> (Pos, Pos) { 3 let re = Regex::new( 4 r"Sensor at x=(?P<x1>[-]?d+), y=(?P<y1>[-]?d+): closest beacon 5 ) 6 .unwrap(); 7 8 let captures = re.captures(line).unwrap(); 9 let sensor = Pos { 10 x: captures["x1"].parse().unwrap(), 11 y: captures["y1"].parse().unwrap(), 12 }; 13 let beacon = Pos { 14 x: captures["x2"].parse().unwrap(), 15 y: captures["y2"].parse().unwrap(), 16 }; 17 (sensor, beacon) 18 } 19 fn parse_line_regex(line: &str) -> (Pos, Pos) { } use regex::Regex; 1 2 3 let re = Regex::new( 4 r"Sensor at x=(?P<x1>[-]?d+), y=(?P<y1>[-]?d+): closest beacon 5 ) 6 .unwrap(); 7 8 let captures = re.captures(line).unwrap(); 9 let sensor = Pos { 10 x: captures["x1"].parse().unwrap(), 11 y: captures["y1"].parse().unwrap(), 12 }; 13 let beacon = Pos { 14 x: captures["x2"].parse().unwrap(), 15 y: captures["y2"].parse().unwrap(), 16 }; 17 (sensor, beacon) 18 19 let re = Regex::new( r"Sensor at x=(?P<x1>[-]?d+), y=(?P<y1>[-]?d+): closest beacon ) .unwrap(); use regex::Regex; 1 2 fn parse_line_regex(line: &str) -> (Pos, Pos) { 3 4 5 6 7 8 let captures = re.captures(line).unwrap(); 9 let sensor = Pos { 10 x: captures["x1"].parse().unwrap(), 11 y: captures["y1"].parse().unwrap(), 12 }; 13 let beacon = Pos { 14 x: captures["x2"].parse().unwrap(), 15 y: captures["y2"].parse().unwrap(), 16 }; 17 (sensor, beacon) 18 } 19 let captures = re.captures(line).unwrap(); use regex::Regex; 1 2 fn parse_line_regex(line: &str) -> (Pos, Pos) { 3 let re = Regex::new( 4 r"Sensor at x=(?P<x1>[-]?d+), y=(?P<y1>[-]?d+): closest beacon 5 ) 6 .unwrap(); 7 8 9 let sensor = Pos { 10 x: captures["x1"].parse().unwrap(), 11 y: captures["y1"].parse().unwrap(), 12 }; 13 let beacon = Pos { 14 x: captures["x2"].parse().unwrap(), 15 y: captures["y2"].parse().unwrap(), 16 }; 17 (sensor, beacon) 18 } 19 let sensor = Pos { x: captures["x1"].parse().unwrap(), y: captures["y1"].parse().unwrap(), }; let beacon = Pos { x: captures["x2"].parse().unwrap(), y: captures["y2"].parse().unwrap(), }; use regex::Regex; 1 2 fn parse_line_regex(line: &str) -> (Pos, Pos) { 3 let re = Regex::new( 4 r"Sensor at x=(?P<x1>[-]?d+), y=(?P<y1>[-]?d+): closest beacon 5 ) 6 .unwrap(); 7 8 let captures = re.captures(line).unwrap(); 9 10 11 12 13 14 15 16 17 (sensor, beacon) 18 } 19 (sensor, beacon) use regex::Regex; 1 2 fn parse_line_regex(line: &str) -> (Pos, Pos) { 3 let re = Regex::new( 4 r"Sensor at x=(?P<x1>[-]?d+), y=(?P<y1>[-]?d+): closest beacon 5 ) 6 .unwrap(); 7 8 let captures = re.captures(line).unwrap(); 9 let sensor = Pos { 10 x: captures["x1"].parse().unwrap(), 11 y: captures["y1"].parse().unwrap(), 12 }; 13 let beacon = Pos { 14 x: captures["x2"].parse().unwrap(), 15 y: captures["y2"].parse().unwrap(), 16 }; 17 18 } 19 use regex::Regex; fn parse_line_regex(line: &str) -> (Pos, Pos) { let re = Regex::new( r"Sensor at x=(?P<x1>[-]?d+), y=(?P<y1>[-]?d+): closest beacon ) .unwrap(); let captures = re.captures(line).unwrap(); let sensor = Pos { x: captures["x1"].parse().unwrap(), y: captures["y1"].parse().unwrap(), }; let beacon = Pos { x: captures["x2"].parse().unwrap(), y: captures["y2"].parse().unwrap(), }; (sensor, beacon) } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 loige 93

pub fn parse_regex(input: &str) -> impl Iterator<Item = (Pos, Pos)> + '_ input.lines().map(parse_line_regex) } use regex::Regex; 1 2 fn parse_line_regex(line: &str) -> (Pos, Pos) { 3 let re = Regex::new( 4 r"Sensor at x=(?P<x1>[-]?d+), y=(?P<y1>[-]?d+): closest beacon 5 ) 6 .unwrap(); 7 8 // ... 9 (sensor, beacon) 10 } 11 12 13 14 15 loige Aren't we re-istantiating the Regex over and over? 🤷 94

How can we initialize the regex globally? loige $ cargo add lazy_static 95

#[macro_use] extern crate lazy_static; use regex::Regex; lazy_static! { static ref LINE_REGEX: Regex = Regex::new(r"Sensor at x=(?P<x1>[-]?d .unwrap(); } fn parse_line_regex(line: &str) -> (Pos, Pos) { let captures = LINE_REGEX.captures(line).unwrap(); // ... (sensor, beacon) } pub fn parse_regex(input: &str) -> impl Iterator<Item = (Pos, Pos)> + '_ input.lines().map(parse_line_regex) } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 #[macro_use] extern crate lazy_static; 1 2 use regex::Regex; 3 4 lazy_static! { 5 static ref LINE_REGEX: Regex = Regex::new(r"Sensor at x=(?P<x1>[-]?d 6 .unwrap(); 7 } 8 9 fn parse_line_regex(line: &str) -> (Pos, Pos) { 10 let captures = LINE_REGEX.captures(line).unwrap(); 11 12 // ... 13 (sensor, beacon) 14 } 15 16 pub fn parse_regex(input: &str) -> impl Iterator<Item = (Pos, Pos)> + '_ 17 input.lines().map(parse_line_regex) 18 } 19 lazy_static! { static ref LINE_REGEX: Regex = Regex::new(r"Sensor at x=(?P<x1>[-]?d .unwrap(); } #[macro_use] 1 extern crate lazy_static; 2 use regex::Regex; 3 4 5 6 7 8 9 fn parse_line_regex(line: &str) -> (Pos, Pos) { 10 let captures = LINE_REGEX.captures(line).unwrap(); 11 12 // ... 13 (sensor, beacon) 14 } 15 16 pub fn parse_regex(input: &str) -> impl Iterator<Item = (Pos, Pos)> + '_ 17 input.lines().map(parse_line_regex) 18 } 19 let captures = LINE_REGEX.captures(line).unwrap(); #[macro_use] 1 extern crate lazy_static; 2 use regex::Regex; 3 4 lazy_static! { 5 static ref LINE_REGEX: Regex = Regex::new(r"Sensor at x=(?P<x1>[-]?d 6 .unwrap(); 7 } 8 9 fn parse_line_regex(line: &str) -> (Pos, Pos) { 10 11 12 // ... 13 (sensor, beacon) 14 } 15 16 pub fn parse_regex(input: &str) -> impl Iterator<Item = (Pos, Pos)> + '_ 17 input.lines().map(parse_line_regex) 18 } 19 #[macro_use] extern crate lazy_static; use regex::Regex; lazy_static! { static ref LINE_REGEX: Regex = Regex::new(r"Sensor at x=(?P<x1>[-]?d .unwrap(); } fn parse_line_regex(line: &str) -> (Pos, Pos) { let captures = LINE_REGEX.captures(line).unwrap(); // ... (sensor, beacon) } pub fn parse_regex(input: &str) -> impl Iterator<Item = (Pos, Pos)> + '_ input.lines().map(parse_line_regex) } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 loige 96

🤷BTW, should I tell you that when you solve a problem with a Regex... BLAH BLAH BLAH?! loige 97

Ok, let's do proper parsing with nom! 💪 loige $ cargo add nom 98

fn parse_i64(input: &str) -> IResult<&str, i64> { let (input, sign) = opt(tag("-"))(input)?; let (input, value) = digit1(input)?; let mut value = value.parse::<i64>().unwrap(); if sign.is_some() { value *= -1; } Ok((input, value)) } 1 2 3 4 5 6 7 8 9 fn parse_i64(input: &str) -> IResult<&str, i64> { } 1 let (input, sign) = opt(tag("-"))(input)?; 2 let (input, value) = digit1(input)?; 3 let mut value = value.parse::<i64>().unwrap(); 4 if sign.is_some() { 5 value *= -1; 6 } 7 Ok((input, value)) 8 9 let (input, sign) = opt(tag("-"))(input)?; fn parse_i64(input: &str) -> IResult<&str, i64> { 1 2 let (input, value) = digit1(input)?; 3 let mut value = value.parse::<i64>().unwrap(); 4 if sign.is_some() { 5 value *= -1; 6 } 7 Ok((input, value)) 8 } 9 let (input, value) = digit1(input)?; fn parse_i64(input: &str) -> IResult<&str, i64> { 1 let (input, sign) = opt(tag("-"))(input)?; 2 3 let mut value = value.parse::<i64>().unwrap(); 4 if sign.is_some() { 5 value *= -1; 6 } 7 Ok((input, value)) 8 } 9 let mut value = value.parse::<i64>().unwrap(); if sign.is_some() { value *= -1; } fn parse_i64(input: &str) -> IResult<&str, i64> { 1 let (input, sign) = opt(tag("-"))(input)?; 2 let (input, value) = digit1(input)?; 3 4 5 6 7 Ok((input, value)) 8 } 9 Ok((input, value)) fn parse_i64(input: &str) -> IResult<&str, i64> { 1 let (input, sign) = opt(tag("-"))(input)?; 2 let (input, value) = digit1(input)?; 3 let mut value = value.parse::<i64>().unwrap(); 4 if sign.is_some() { 5 value *= -1; 6 } 7 8 } 9 fn parse_i64(input: &str) -> IResult<&str, i64> { let (input, sign) = opt(tag("-"))(input)?; let (input, value) = digit1(input)?; let mut value = value.parse::<i64>().unwrap(); if sign.is_some() { value *= -1; } Ok((input, value)) } 1 2 3 4 5 6 7 8 9 loige 99

fn parse_line(input: &str) -> IResult<&str, (Pos, Pos)> { let (input, (s_x, s_y, b_x, b_y)) = all_consuming(tuple(( preceded(tag("Sensor at x="), parse_i64), preceded(tag(", y="), parse_i64), preceded(tag(": closest beacon is at x="), parse_i64), preceded(tag(", y="), parse_i64), )))(input)?; let p1 = Pos { x: s_x, y: s_y }; let p2 = Pos { x: b_x, y: b_y }; Ok((input, (p1, p2))) } 1 2 3 4 5 6 7 8 9 10 11 fn parse_line(input: &str) -> IResult<&str, (Pos, Pos)> { } 1 let (input, (s_x, s_y, b_x, b_y)) = all_consuming(tuple(( 2 preceded(tag("Sensor at x="), parse_i64), 3 preceded(tag(", y="), parse_i64), 4 preceded(tag(": closest beacon is at x="), parse_i64), 5 preceded(tag(", y="), parse_i64), 6 )))(input)?; 7 let p1 = Pos { x: s_x, y: s_y }; 8 let p2 = Pos { x: b_x, y: b_y }; 9 Ok((input, (p1, p2))) 10 11 let (input, (s_x, s_y, b_x, b_y)) = all_consuming(tuple(( preceded(tag("Sensor at x="), parse_i64), preceded(tag(", y="), parse_i64), preceded(tag(": closest beacon is at x="), parse_i64), preceded(tag(", y="), parse_i64), )))(input)?; fn parse_line(input: &str) -> IResult<&str, (Pos, Pos)> { 1 2 3 4 5 6 7 let p1 = Pos { x: s_x, y: s_y }; 8 let p2 = Pos { x: b_x, y: b_y }; 9 Ok((input, (p1, p2))) 10 } 11 let p1 = Pos { x: s_x, y: s_y }; let p2 = Pos { x: b_x, y: b_y }; fn parse_line(input: &str) -> IResult<&str, (Pos, Pos)> { 1 let (input, (s_x, s_y, b_x, b_y)) = all_consuming(tuple(( 2 preceded(tag("Sensor at x="), parse_i64), 3 preceded(tag(", y="), parse_i64), 4 preceded(tag(": closest beacon is at x="), parse_i64), 5 preceded(tag(", y="), parse_i64), 6 )))(input)?; 7 8 9 Ok((input, (p1, p2))) 10 } 11 Ok((input, (p1, p2))) fn parse_line(input: &str) -> IResult<&str, (Pos, Pos)> { 1 let (input, (s_x, s_y, b_x, b_y)) = all_consuming(tuple(( 2 preceded(tag("Sensor at x="), parse_i64), 3 preceded(tag(", y="), parse_i64), 4 preceded(tag(": closest beacon is at x="), parse_i64), 5 preceded(tag(", y="), parse_i64), 6 )))(input)?; 7 let p1 = Pos { x: s_x, y: s_y }; 8 let p2 = Pos { x: b_x, y: b_y }; 9 10 } 11 fn parse_line(input: &str) -> IResult<&str, (Pos, Pos)> { let (input, (s_x, s_y, b_x, b_y)) = all_consuming(tuple(( preceded(tag("Sensor at x="), parse_i64), preceded(tag(", y="), parse_i64), preceded(tag(": closest beacon is at x="), parse_i64), preceded(tag(", y="), parse_i64), )))(input)?; let p1 = Pos { x: s_x, y: s_y }; let p2 = Pos { x: b_x, y: b_y }; Ok((input, (p1, p2))) } 1 2 3 4 5 6 7 8 9 10 11 loige 100

Which one do you think is faster? 🧐 loige regex regex_lazy nom 1. 2. 3. 101

Which one do you think is faster? 🧐 loige regex regex_lazy nom 1. 2. 3. 102

Which one do you think is faster? 🧐 loige regex regex_lazy nom 1. 2. 3. 3063.9 µs 9.3 µs 1.8 µs ⭐ +170117% +417% 103

The Iterator & the FromIterator traits Destructuring with if let Some(x) / while let Some(x)... Powerful pattern-matching syntax and the matches!() macro Newtype pattern + Deref & DerefMut trait The Display & Debug traits unreachable!() & todo!() macros defaultdict a-la-python using HashMap and the entry API Copy On Write (CoW) Helper methods of the Result and the Option types I would have also loved to tell you about... 🤯 104

Started with a very imperative style and ended up with a more functional style "if you look back at your code from 2 years ago and you are not ashamed you are not growing" Noticed that rust has been improving a lot in these 3 years Often needed helpers but they were in nightly (Vec::retain) Rust Analyser & Clippy have been suggesting new improvements over time! Rust is fantastic for Advent of Code! 🦀In conclusion... 105

Photo by on Nathan Dumlao Unsplash loige 106

Huge thanks to , , Cover photo by on @gbinside @AlleviTommaso @giufus Redaviqui Davilli Unsplash TNX loige nodejsdp.link Sorry, I have a contractual obligation to put this here 😛 107

What I learned by solving 50 Advent of Code challenges in Rust - RustNation UK 2023

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What I learned by solving 50 Advent of Code challenges in Rust - RustNation UK 2023