Use strings for output types in Rust

This is a compromise that gets us most of the way towards what we have with the heterogeneous list in Haskell, but without any complex abstractions.

rust/main.rs

@@ -3,7 +3,6 @@ mod puzzles;
 use crate::puzzle::Puzzle;
 use puzzles::day1;
 use puzzles::day2;
-use std::fmt::Display;
 use std::fs;
 
 const PUZZLES: [&dyn SomePuzzle; 2] = [&day1::PUZZLE, &day2::PUZZLE];
@@ -39,12 +38,12 @@ pub trait SomePuzzle {
     fn number(&self) -> u32;
     fn run(&self, input: &str) -> Vec<String>;
 }
-impl<Input, Output: Display, const N: usize> SomePuzzle for Puzzle<Input, Output, { N }> {
+impl<Input, const N: usize> SomePuzzle for Puzzle<Input, { N }> {
     fn number(&self) -> u32 {
         self.number
     }
     fn run(&self, s: &str) -> Vec<String> {
         let input = (self.parser)(s);
-        self.parts.map(|p| p(&input).to_string() + "\n").to_vec()
+        self.parts.map(|p| p(&input) + "\n").to_vec()
     }
 }

rust/puzzle.rs

@@ -1,5 +1,5 @@
-pub struct Puzzle<Input, Output, const N: usize> {
+pub struct Puzzle<Input, const N: usize> {
     pub number: u32,
     pub parser: fn(&str) -> Input,
-    pub parts: [fn(&Input) -> Output; N],
+    pub parts: [fn(&Input) -> String; N],
 }

rust/puzzles/day1.rs

@@ -9,7 +9,7 @@ use nom::{
     sequence::{pair, terminated},
 };
 
-pub const PUZZLE: Puzzle<Vec<(Direction, i32)>, i32, 2> = Puzzle {
+pub const PUZZLE: Puzzle<Vec<(Direction, i32)>, 2> = Puzzle {
     number: 1,
     parser: |input| {
         terminated(
@@ -43,7 +43,7 @@ pub const PUZZLE: Puzzle<Vec<(Direction, i32)>, i32, 2> = Puzzle {
                 }
                 p = p1;
             }
-            r
+            r.to_string()
         },
         |instructions| {
             let mut p = 50;
@@ -65,7 +65,7 @@ pub const PUZZLE: Puzzle<Vec<(Direction, i32)>, i32, 2> = Puzzle {
                 r += c1;
                 p = p1;
             }
-            r
+            r.to_string()
         },
     ],
 };

rust/puzzles/day2.rs

@@ -8,7 +8,7 @@ use nom::{
     sequence::{separated_pair, terminated},
 };
 
-pub const PUZZLE: Puzzle<Vec<(usize, usize)>, usize, 2> = Puzzle {
+pub const PUZZLE: Puzzle<Vec<(usize, usize)>, 2> = Puzzle {
     number: 2,
     parser: |input| {
         terminated(
@@ -32,7 +32,8 @@ pub const PUZZLE: Puzzle<Vec<(usize, usize)>, usize, 2> = Puzzle {
                 .flat_map(|(l, u)| {
                     (*l..(u + 1)).flat_map(|n| if is_repetition_2(n) { Some(n) } else { None })
                 })
-                .sum()
+                .sum::<usize>()
+                .to_string()
         },
         |input| {
             input
@@ -40,7 +41,8 @@ pub const PUZZLE: Puzzle<Vec<(usize, usize)>, usize, 2> = Puzzle {
                 .flat_map(|(l, u)| {
                     (*l..(u + 1)).flat_map(|n| if is_repetition_n(n) { Some(n) } else { None })
                 })
-                .sum()
+                .sum::<usize>()
+                .to_string()
         },
     ],
 };