refactor: use Result<T, E> instead of .unwrap()

README.md

@@ -2,6 +2,7 @@
 
 https://adventofcode.com/2021
 
+Error handling: http://web.mit.edu/rust-lang_v1.25/arch/amd64_ubuntu1404/share/doc/rust/html/book/first-edition/error-handling.html#a-brief-interlude-unwrapping-isnt-evil
 
 ## Resources
 * https://github.com/ithinuel/advent-of-code-rust/tree/2020/src/bin

src/day1.rs

@@ -1,13 +1,22 @@
 use std::fs::File;
-use std::io::prelude::*;
+use std::io::{prelude::*, self};
+use std::num::ParseIntError;
 
-pub fn input_from_file(filename: &str) -> Vec<u32> {
+#[derive(Debug)]
-    let mut file = File::open(filename).expect("Can't open file");
+pub enum InputFromFileError {
+    ParseIntError(ParseIntError),
+    IoError(io::Error),
+}
+
+pub fn input_from_file(filename: &str) -> Result<Vec<u32>, InputFromFileError> {
+    let mut file = File::open(filename).map_err(InputFromFileError::IoError)?;
 
     let mut contents = String::new();
-    file.read_to_string(&mut contents).expect("Oops! Can not read the file...");
+    file.read_to_string(&mut contents).map_err(InputFromFileError::IoError)?;
 
-    return contents.split_whitespace().map(|s| s.parse::<u32>().unwrap()).collect();
+    contents.split_whitespace()
+        .map(|s| s.parse().map_err(InputFromFileError::ParseIntError))
+        .collect()
 }
 
 pub fn part1(depths: &[u32]) -> u32 {

src/main.rs

@@ -2,7 +2,8 @@ mod day1;
 
 fn main() {
     let input_filename = "input.txt";
-    let input = day1::input_from_file(input_filename);
+    let input = day1::input_from_file(input_filename)
+        .expect("Failed to read input.txt");
     let result1 = day1::part1(&input);
     let result2 = day1::part2(&input);
     println!("Part 1 result: {}", result1);