From b561e148e01b94452abeb45cfaa4e63166671331 Mon Sep 17 00:00:00 2001
From: mat ess <mat@mat.services>
Date: Sun, 4 Dec 2022 19:20:16 -0500
Subject: [PATCH] Add solutions macro

---
 src/main.rs | 45 +++++++++++++++++++++++++++------------------
 1 file changed, 27 insertions(+), 18 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index bdeff1e..3f072e5 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -6,26 +6,19 @@ use anyhow::Error;
 use chrono::{Datelike, Local};
 use pico_args::Arguments;
 
-fn main() -> Result<(), Error> {
-    let mut args = Arguments::from_env();
-    let small = args.contains("--small");
-    let part = args.opt_free_from_str()?.unwrap_or(1);
-    let day = args
-        .opt_free_from_str()?
-        .unwrap_or_else(|| Local::now().day());
-    let small = if small { ".small" } else { "" };
-    let path = format!("inputs/{day}{small}.txt");
-    let input = fs::read_to_string(path)?;
-    println!("running day {day} part {part}");
-    let result = SOLNS[day as usize - 1][part as usize - 1](input);
-    println!("{result}");
-    Ok(())
+macro_rules! solutions {
+    ($($all:tt),*) => {
+        const DAYS: usize = 0 $( + solutions!(@expand $all 1) )*;
+        const SOLUTIONS: [Day; DAYS] = [
+            $($all),*
+        ];
+    };
+    (@expand $ignore:tt $e:expr) => {$e};
 }
 
 type Part = fn(String) -> u64;
 type Day = [Part; 2];
-const DAYS: usize = 4;
-const SOLNS: [Day; DAYS] = [
+solutions! {
     [
         // day 1 part 1
         |input| {
@@ -136,8 +129,24 @@ const SOLNS: [Day; DAYS] = [
                 .map(|b| if b { 1 } else { 0 })
                 .sum()
         },
-    ],
-];
+    ]
+}
+
+fn main() -> Result<(), Error> {
+    let mut args = Arguments::from_env();
+    let small = args.contains("--small");
+    let part = args.opt_free_from_str()?.unwrap_or(1);
+    let day = args
+        .opt_free_from_str()?
+        .unwrap_or_else(|| Local::now().day());
+    let small = if small { ".small" } else { "" };
+    let path = format!("inputs/{day}{small}.txt");
+    let input = fs::read_to_string(path)?;
+    println!("running day {day} part {part}");
+    let result = SOLUTIONS[day as usize - 1][part as usize - 1](input);
+    println!("{result}");
+    Ok(())
+}
 
 fn make_ranges(input: String) -> Vec<(Range<u64>, Range<u64>)> {
     input