From 6cc7cb8752b072c8027f3f73bd4539547185ba14 Mon Sep 17 00:00:00 2001
From: Joseph Montanaro <jfmontanaro@modg.org>
Date: Tue, 14 Dec 2021 11:26:24 -0800
Subject: [PATCH] add Vec2 to lib.rs

---
 2021/src/lib.rs | 50 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/2021/src/lib.rs b/2021/src/lib.rs
index f991069..8b658ce 100644
--- a/2021/src/lib.rs
+++ b/2021/src/lib.rs
@@ -1,6 +1,7 @@
 use std::io::Read;
 use std::str::FromStr;
 use std::fs::File;
+use std::ops::{Index, IndexMut};
 
 use color_eyre::{eyre};
 use eyre::eyre;
@@ -69,3 +70,52 @@ pub trait IterExt: Iterator {
 }
 
 impl<I: Iterator> IterExt for I {}
+
+
+// 2d container, functions kind of like a "vec of vecs" but all data is stored in a single vec for memory contiguity
+pub struct Vec2<T> {
+    data: Vec<T>,
+    columns: usize,
+}
+
+
+impl<T> Vec2<T> {
+    fn new(columns: usize) -> Vec2<T> {
+        Vec2 {data: Vec::<T>::new(), columns}
+    }
+
+    fn push<S: IntoIterator<Item=T>>(&mut self, row: S) {
+        self.data.extend(row.into_iter());
+    }
+    
+    // This works just fine, for some reason
+    fn rows(&self) -> impl Iterator<Item=&[T]> {
+        self.data.chunks_exact(self.columns)
+    }
+
+    // But this doesn't? 
+    fn rows_mut(&mut self) -> impl Iterator<Item=&mut [T]> {
+        self.data.chunks_exact_mut(self.columns)
+    }
+    
+    fn values(&self) -> impl Iterator<Item=&T> {
+        self.data.iter()
+    }
+}
+
+
+impl<T> Index<usize> for Vec2<T> {
+    type Output = [T];
+    fn index(&self, index: usize) -> &Self::Output {
+        let start = self.columns * index;
+        &self.data[start..(start + self.columns)]
+    }
+}
+
+
+impl<T> IndexMut<usize> for Vec2<T> {
+    fn index_mut(&mut self, index: usize) -> &mut Self::Output {
+        let start = self.columns * index;
+        &mut self.data[start..(start + self.columns)]
+    }
+}