From 03513b9f020319799fcc1104b2cc9d8ec6bdbf04 Mon Sep 17 00:00:00 2001
From: Olivia Appleton <liv@OliviaAppleton.com>
Date: Mon, 8 Jul 2024 23:15:14 -0500
Subject: [PATCH] Add partial rust prime infrastructure

---
 .gitignore         |  3 ++-
 rust/src/main.rs   | 19 +++++++++++++
 rust/src/primes.rs | 66 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 87 insertions(+), 1 deletion(-)
 create mode 100644 rust/src/primes.rs

diff --git a/.gitignore b/.gitignore
index fe0b1aa9..b1bcc5f4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -13,4 +13,5 @@ venv/**
 csharp/*/obj
 csharp/*/bin
 **/TestResults
-docs/_build
\ No newline at end of file
+docs/_build
+rust/target
\ No newline at end of file
diff --git a/rust/src/main.rs b/rust/src/main.rs
index 35d55897..8953b578 100644
--- a/rust/src/main.rs
+++ b/rust/src/main.rs
@@ -1,5 +1,7 @@
 #[cfg(test)]
 use std::time::Duration;
+// #[cfg(test)]
+// use std::iter::zip;
 
 use seq_macro::seq;
 #[cfg(test)]
@@ -8,6 +10,7 @@ use rstest::rstest;
 seq!(N in 0001..=0002 {
 mod p~N;
 });
+mod primes;
 
 type ProblemType = fn() -> u64;
 type ProblemRef<'a> = (&'a str, ProblemType, u64);
@@ -17,6 +20,10 @@ const ANSWERS: [ProblemRef; 2] = [
 ];
 
 fn main() {
+    // let sieve = primes::ModifiedEratosthenes::new().take(10);
+    // for i in sieve {
+    //     println!("{}", i);
+    // }
     for (name, func, answer) in ANSWERS {
         let result = func();
         println!("Problem {} should return {}. Returned {}!", name, answer, result);
@@ -37,3 +44,15 @@ fn test_problem(#[case] idx: usize) -> Result<(), String> {
     Ok(())
 }
 });
+
+
+// #[cfg(test)]
+// #[test]
+// fn test_primes() -> Result<(), String> {
+//     let primes = [2, 3, 5, 7, 11, 13, 17, 19];
+//     let sieve = primes::ModifiedEratosthenes::new().take(primes.len());
+//     for (p, s) in zip(primes, sieve) {
+//         assert_eq!(p, s);
+//     }
+//     Ok(())
+// }
diff --git a/rust/src/primes.rs b/rust/src/primes.rs
new file mode 100644
index 00000000..e406495a
--- /dev/null
+++ b/rust/src/primes.rs
@@ -0,0 +1,66 @@
+use std::collections::HashMap;
+
+pub struct ModifiedEratosthenes {
+    sieve: HashMap<u64, u64>,
+    prime: u64,
+    candidate: u64,
+    recurse: Option<Box<ModifiedEratosthenes>>
+}
+
+impl ModifiedEratosthenes {
+    pub fn new() -> ModifiedEratosthenes {
+        return ModifiedEratosthenes{
+            sieve: HashMap::new(),
+            prime: 0,
+            candidate: 2,
+            recurse: None
+        };
+    }
+}
+
+impl Iterator for ModifiedEratosthenes {
+    type Item = u64;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.candidate == 2 {
+            self.candidate = 3;
+            self.prime = 3;
+            println!("Returning 2");
+            return Some(2);
+        }
+        let mut candidate = self.candidate;
+        self.candidate += 2;
+        loop {
+            let prime_squared = self.prime * self.prime;
+            println!("Candidate: {}", candidate);
+            let step: u64;
+            if self.sieve.contains_key(&candidate) {
+                step = self.sieve.remove(&candidate)?;
+                println!("Candidate in cache as {}", step);
+            }
+            else if candidate < prime_squared {
+                println!("Candidate not in cache, but less than {}", prime_squared);
+                return Some(candidate);
+            }
+            else {
+                if candidate != prime_squared {
+                    panic!("Something has gone wrong in the sieve");
+                }
+                step = self.prime * 2;
+                if self.recurse.is_none() {
+                    self.recurse = Some(Box::new(ModifiedEratosthenes::new()));
+                    let mut recursed = self.recurse.take()?;
+                    let _ = (*recursed).next();
+                }
+                let mut recursed = self.recurse.take()?;
+                self.prime = ((*recursed).next())?;
+            }
+            println!("This is the good part");
+            candidate += step;
+            while self.sieve.contains_key(&candidate) {
+                candidate += step;
+            }
+            self.sieve.insert(candidate, step);
+        }
+    }
+}
\ No newline at end of file