Do Day 2, playing around with nom v6

Cargo.toml

@@ -5,3 +5,4 @@ authors = ["Adam Wick <awick@uhsure.com>"]
 edition = "2018"
 
 [dependencies]
+nom = "6.0.1"

inputs/day2_test.txt

@@ -0,0 +1,3 @@
+1-3 a: abcde
+1-3 b: cdefg
+2-9 c: ccccccccc

src/bin/accounting.rs

@@ -7,7 +7,7 @@ use std::str::FromStr;
 fn real_main() -> Result<(), TopLevelError> {
     let mut numbers = Vec::new();
 
-    for argument in env::args().skip(2) {
+    for argument in env::args().skip(1) {
         let contents = fs::read_to_string(argument)?;
         for line in contents.lines() {
             match u64::from_str(line) {

src/bin/password_check.rs

@@ -0,0 +1,97 @@
+use advent2020::errors::{PasswordParseError, TopLevelError};
+use nom::character::complete::{anychar, char, digit1, multispace1};
+use std::env;
+use std::fs;
+use std::str::FromStr;
+
+struct PasswordData {
+    first_number: usize,
+    second_number: usize,
+    character: char,
+    password: String,
+}
+
+impl FromStr for PasswordData {
+    type Err = PasswordParseError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let (rest0, min_chars) = digit1(s)?;
+        let (rest1, _) = char('-')(rest0)?;
+        let (rest2, max_chars) = digit1(rest1)?;
+        let (rest3, _) = multispace1(rest2)?;
+        let (rest4, character) = anychar(rest3)?;
+        let (rest5, _) = char(':')(rest4)?;
+        let (password_chars, _) = multispace1(rest5)?;
+
+        let min_count = usize::from_str(min_chars)?;
+        let max_count = usize::from_str(max_chars)?;
+        let password = password_chars.to_string();
+
+        Ok(PasswordData {
+            first_number: min_count,
+            second_number: max_count,
+            character,
+            password,
+        })
+    }
+}
+
+impl PasswordData {
+    fn is_valid_interpretation1(&self) -> bool {
+        let count = self.password.chars().filter(|x| *x == self.character).count();
+        (count >= self.first_number) && (count <= self.second_number)
+    }
+
+    fn is_valid_interpretation2(&self) -> bool {
+        let mut first_matches = false;
+        let mut second_matches = false;
+
+        for (idx, char) in self.password.char_indices() {
+            if (idx + 1) == self.first_number {
+                first_matches = char == self.character;
+            }
+
+            if (idx + 1) == self.second_number {
+                second_matches = char == self.character;
+            }
+        }
+
+        first_matches ^ second_matches
+    }
+}
+
+
+fn real_main() -> Result<(), TopLevelError> {
+    let mut good_items_interpretation1 = 0u64;
+    let mut good_items_interpretation2 = 0u64;
+
+    for argument in env::args().skip(1) {
+        println!("Processing {}", argument);
+        let contents = fs::read_to_string(argument)?;
+        for line in contents.lines() {
+            match PasswordData::from_str(line) {
+                Err(e) => eprintln!("Skipping line with '{}': {}", line, e),
+                Ok(v) => {
+                    if v.is_valid_interpretation1() {
+                        good_items_interpretation1 += 1;
+                    }
+                    if v.is_valid_interpretation2() {
+                        good_items_interpretation2 += 1;
+                    }
+                }
+            }
+        }
+    }
+
+    println!("# of good passwords, according to interpretation #1: {}", good_items_interpretation1);
+    println!("# of good passwords, according to interpretation #2: {}", good_items_interpretation2);
+
+    Ok(())
+}
+
+fn main() {
+    match real_main() {
+        Err(e) => eprintln!("ERROR: {}", e),
+        Ok(_) => {}
+    }
+}

src/errors.rs

@@ -1,5 +1,17 @@
+use nom;
 use std::fmt;
 use std::io;
+use std::num::ParseIntError;
+
+macro_rules! convert_error {
+    ($type: ty, $super_type: ident, $pattern: ident) => {
+        impl From<$type> for $super_type {
+            fn from(x: $type) -> $super_type {
+                $super_type::$pattern(x)
+            }
+        }
+    };
+}
 
 pub enum TopLevelError {
     IOError(io::Error),
@@ -19,14 +31,21 @@ impl fmt::Display for TopLevelError {
     }
 }
 
-macro_rules! convert_error {
-    ($type: ty, $pattern: ident) => {
-        impl From<$type> for TopLevelError {
-            fn from(x: $type) -> TopLevelError {
-                TopLevelError::$pattern(x)
-            }
-        }
-    };
+convert_error!(io::Error, TopLevelError, IOError);
+
+pub enum PasswordParseError {
+    StringToIntError(ParseIntError),
+    NomError(nom::Err<()>)
 }
 
-convert_error!(io::Error, IOError);
+impl fmt::Display for PasswordParseError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            PasswordParseError::NomError(e) => write!(f, "Parse error: {}", e),
+            PasswordParseError::StringToIntError(e) => write!(f, "Error converting string to integer: {}", e),
+        }
+    }
+}
+
+convert_error!(ParseIntError, PasswordParseError, StringToIntError);
+convert_error!(nom::Err<()>, PasswordParseError, NomError);