A bit of an overly-fussy implementation for Day 3.

src/map.rs

@@ -0,0 +1,55 @@
+use crate::errors::MapParseError;
+use std::convert::TryFrom;
+
+pub struct Map<A: Clone> {
+    width: usize,
+    _height: usize,
+    data: Vec<Vec<A>>,
+}
+
+impl<'a, E, X> TryFrom<&'a str> for Map<X>
+where
+    X: Clone + TryFrom<char, Error = E>,
+    E: From<MapParseError>,
+{
+    type Error = E;
+
+    fn try_from(s: &str) -> Result<Map<X>, E> {
+        let mut width = 0;
+        let mut _height = 0;
+        let mut data = Vec::new();
+
+        for line in s.lines() {
+            let mut current_line = Vec::with_capacity(width);
+
+            for char in line.chars() {
+                let item = X::try_from(char)?;
+                current_line.push(item);
+            }
+
+            _height += 1;
+            if width == 0 {
+                width = current_line.len();
+            } else {
+                if width != current_line.len() {
+                    return Err(E::from(MapParseError::UnevenLines(_height)));
+                }
+            }
+            data.push(current_line);
+        }
+
+        Ok(Map {
+            width,
+            _height,
+            data,
+        })
+    }
+}
+
+impl<X: Clone> Map<X> {
+    pub fn at(&self, x: usize, y: usize) -> Option<X> {
+        let row = self.data.get(y)?;
+        let wrapped_x = x % self.width;
+        Some(row[wrapped_x].clone())
+    }
+}