AAAAAAAAAAAAAAAAAAAAAAAAa

src/connect4/board.rs

@@ -1,6 +1,9 @@
-use std::ops::Index;
+use std::{
+    fmt::{Display, Write},
+    ops::{Index, IndexMut},
+};
 
-use crate::{Player, State};
+use crate::{minmax::Score, Game, GamePlayer, Player, State};
 
 type Position = Option<Player>;
 
@@ -12,11 +15,12 @@ const BOARD_POSITIONS: usize = WIDTH * HEIGTH;
 ///  7  8  9 10 11 12 13
 /// 14 15 16 17 18 19 20
 /// 21 22 23 24 25 26 27
-pub struct Board {
+#[derive(Clone)]
+pub struct Connect4 {
     positions: [Position; BOARD_POSITIONS],
 }
 
-impl Board {
+impl Connect4 {
     pub fn new() -> Self {
         Self {
             positions: [None; BOARD_POSITIONS],
@@ -86,9 +90,30 @@ impl Board {
             })
             .unwrap_or(State::InProgress)
     }
+
+    fn rate(&self, player: Player) -> Score {
+        #[rustfmt::skip]
+        const WIN_COUNT_TABLE: [i32; BOARD_POSITIONS] = [
+            3, 4, 6, 7, 6, 4, 3,
+            2, 4, 6, 7, 6, 4, 2,
+            2, 4, 6, 7, 6, 4, 2,
+            3, 4, 6, 7, 6, 4, 2,
+        ];
+
+        let score_player = |player: Player| {
+            self.positions
+                .iter()
+                .enumerate()
+                .filter(|(_, state)| **state == Some(player))
+                .map(|(pos, _)| WIN_COUNT_TABLE[pos])
+                .sum::<i32>()
+        };
+
+        Score::new(score_player(player) - score_player(player.opponent()))
+    }
 }
 
-impl Index<usize> for Board {
+impl Index<usize> for Connect4 {
     type Output = Position;
 
     fn index(&self, index: usize) -> &Self::Output {
@@ -96,13 +121,87 @@ impl Index<usize> for Board {
     }
 }
 
+impl IndexMut<usize> for Connect4 {
+    fn index_mut(&mut self, index: usize) -> &mut Self::Output {
+        &mut self.positions[index]
+    }
+}
+
+impl Game for Connect4 {
+    type Move = usize;
+
+    const REASONABLE_SEARCH_DEPTH: Option<usize> = Some(5);
+
+    fn empty() -> Self {
+        Self::new()
+    }
+
+    fn possible_moves(&self) -> impl Iterator<Item = Self::Move> {
+        let board = self.clone();
+        (0..WIDTH).filter(move |col| board[*col].is_none())
+    }
+
+    fn result(&self) -> State {
+        Connect4::result(&self)
+    }
+
+    fn make_move(&mut self, position: Self::Move, player: Player) {
+        for i in 0..3 {
+            let prev = position + (i * WIDTH);
+            let next = position + ((i + 1) * WIDTH);
+
+            if self[next].is_some() {
+                self[prev] = Some(player);
+                break;
+            }
+        }
+
+        let bottom = position + (3 * WIDTH);
+        self[bottom] = Some(player);
+    }
+
+    fn undo_move(&mut self, position: Self::Move) {
+        for i in 0..4 {
+            let pos = position + (i * WIDTH);
+
+            if self[pos].is_some() {
+                self[pos] = None;
+            }
+        }
+    }
+
+    fn rate(&self, player: Player) -> Score {
+        Connect4::rate(&self, player)
+    }
+}
+
+impl Display for Connect4 {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        for i in 0..HEIGTH {
+            for j in 0..WIDTH {
+                let index = (i * WIDTH) + j;
+                match self[index] {
+                    Some(player) => {
+                        write!(f, "\x1B[33m  {player}\x1B[0m  ")?;
+                    }
+                    None => {
+                        write!(f, "\x1B[35m{index:3 }\x1B[0m  ")?;
+                    }
+                }
+            }
+            f.write_char('\n')?;
+        }
+        Ok(())
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use crate::{Player, State};
 
-    use super::Board;
+    use super::Connect4;
 
-    fn parse_board(board: &str) -> Board {
+    fn parse_board(board: &str) -> Connect4 {
         let positions = board
             .chars()
             .filter(|char| !char.is_whitespace())
@@ -119,7 +218,7 @@ mod tests {
                 board.chars().filter(|c| !c.is_whitespace()).count()
             ));
 
-        Board { positions }
+        Connect4 { positions }
     }
 
     fn test(board: &str, state: State) {

src/connect4/mod.rs

@@ -1 +1,6 @@
-pub mod board;
+use self::board::Connect4;
+
+pub use player::HumanPlayer;
+
+pub mod board;
+pub mod player;

src/connect4/player.rs

@@ -0,0 +1,35 @@
+use std::io::Write;
+
+use crate::{Game, GamePlayer, Player};
+
+use super::Connect4;
+
+#[derive(Clone, Default)]
+pub struct HumanPlayer;
+
+impl GamePlayer<Connect4> for HumanPlayer {
+    fn next_move(&mut self, board: &mut Connect4, this_player: Player) {
+        loop {
+            print!("{board}where to put the next {this_player}? (0-7): ");
+
+            std::io::stdout().flush().unwrap();
+            let mut buf = String::new();
+            std::io::stdin().read_line(&mut buf).unwrap();
+
+            match buf.trim().parse() {
+                Ok(number) if number < 7 => match board[number] {
+                    None => {
+                        board.make_move(number, this_player);
+                        return;
+                    }
+                    Some(_) => {
+                        println!("Field is occupied already.")
+                    }
+                },
+                Ok(_) | Err(_) => {
+                    println!("Invalid input.")
+                }
+            }
+        }
+    }
+}

src/lib.rs

@@ -1,4 +1,9 @@
-#![feature(never_type, try_trait_v2, return_position_impl_trait_in_trait)]
+#![feature(
+    never_type,
+    try_trait_v2,
+    return_position_impl_trait_in_trait,
+    let_chains
+)]
 #![allow(incomplete_features)]
 
 pub mod connect4;
@@ -7,13 +12,56 @@ pub mod tic_tac_toe;
 
 mod player;
 
-use self::minmax::GameBoard;
+use std::fmt::Display;
+
+use minmax::Score;
 pub use player::{Player, State};
 
-pub trait Game {
-    type Board: GameBoard;
+pub trait GamePlayer<G: ?Sized + Game>: Default {
+    fn next_move(&mut self, board: &mut G, this_player: Player);
 }
 
-pub trait GamePlayer<G: Game>: Default {
-    fn next_move(&mut self, board: &mut G::Board, this_player: Player);
+pub trait Game: Display {
+    type Move: Copy;
+
+    const REASONABLE_SEARCH_DEPTH: Option<usize>;
+
+    fn empty() -> Self;
+
+    fn possible_moves(&self) -> impl Iterator<Item = Self::Move>;
+
+    fn result(&self) -> State;
+
+    /// Only called if [`GameBoard::REASONABLE_SEARCH_DEPTH`] is `Some`.
+    fn rate(&self, player: Player) -> Score;
+
+    fn make_move(&mut self, position: Self::Move, player: Player);
+
+    fn undo_move(&mut self, position: Self::Move);
+
+    fn play<A: GamePlayer<Self>, B: GamePlayer<Self>>(
+        &mut self,
+        x: &mut A,
+        o: &mut B,
+    ) -> Option<Player> {
+        let mut current_player = Player::X;
+
+        loop {
+            if current_player == Player::X {
+                x.next_move(self, current_player);
+            } else {
+                o.next_move(self, current_player);
+            }
+
+            match self.result() {
+                State::Winner(player) => return Some(player),
+                State::Draw => {
+                    return None;
+                }
+                State::InProgress => {}
+            }
+
+            current_player = current_player.opponent();
+        }
+    }
 }

src/main.rs

@@ -1,19 +1,25 @@
 #![allow(unused_imports)]
 
-use std::time::SystemTime;
+use std::{fmt::Display, time::SystemTime};
 
 use minmax::{
-    tic_tac_toe::{Board, GreedyPlayer, HumanPlayer, PerfectPlayer, TicTacToe},
-    GamePlayer, Player,
+    connect4::{self, board::Connect4},
+    tic_tac_toe::{GreedyPlayer, HumanPlayer, PerfectPlayer, TicTacToe},
+    Game, GamePlayer, Player,
 };
 
 fn main() {
+    play::<connect4::HumanPlayer, connect4::HumanPlayer, _>(true);
+}
+
+#[allow(dead_code)]
+fn tic_tac_toe_stats() {
     let mut results = [0, 0, 0];
 
     let start = SystemTime::now();
 
     for _ in 0..100 {
-        let result = play_round::<PerfectPlayer, GreedyPlayer>(false);
+        let result = play::<PerfectPlayer, GreedyPlayer, _>(false);
         let idx = Player::as_u8(result);
         results[idx as usize] += 1;
     }
@@ -28,23 +34,24 @@ fn main() {
     println!("Completed in {}ms", time.as_millis());
 }
 
-fn play_round<X: GamePlayer<TicTacToe>, O: GamePlayer<TicTacToe>>(print: bool) -> Option<Player> {
-    let mut board = Board::empty();
+fn play<X: GamePlayer<G>, O: GamePlayer<G>, G: Game>(print: bool) -> Option<Player> {
+    let mut board = G::empty();
     let result = board.play(&mut X::default(), &mut O::default());
     if print {
-        println!("{board}");
-    }
-    match result {
-        Some(winner) => {
-            if print {
-                println!("player {winner} won!");
-            }
-        }
-        None => {
-            if print {
-                println!("a draw...")
-            }
-        }
+        print_result(result, board);
     }
     result
 }
+
+fn print_result(result: Option<Player>, board: impl Display) {
+    println!("{board}");
+
+    match result {
+        Some(winner) => {
+            println!("player {winner} won!");
+        }
+        None => {
+            println!("a draw...")
+        }
+    }
+}

src/minmax.rs

@@ -2,25 +2,17 @@ use std::ops::Neg;
 
 use crate::{Game, GamePlayer, Player, State};
 
-pub trait GameBoard {
-    type Move: Copy;
-
-    fn possible_moves(&self) -> impl Iterator<Item = Self::Move>;
-
-    fn result(&self) -> State;
-
-    fn make_move(&mut self, position: Self::Move, player: Player);
-
-    fn undo_move(&mut self, position: Self::Move);
-}
-
 #[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]
-pub struct Score(i8);
+pub struct Score(i32);
 
 impl Score {
-    const LOST: Self = Self(i8::MIN);
+    const LOST: Self = Self(i32::MIN);
     const TIE: Self = Self(0);
-    const WON: Self = Self(i8::MAX);
+    const WON: Self = Self(i32::MAX);
+
+    pub fn new(int: i32) -> Self {
+        Self(int)
+    }
 }
 
 impl Neg for Score {
@@ -32,25 +24,26 @@ impl Neg for Score {
 }
 
 #[derive(Clone)]
-pub struct PerfectPlayer<B: GameBoard> {
+pub struct PerfectPlayer<B: Game> {
     best_move: Option<B::Move>,
 }
 
-impl<B: GameBoard> Default for PerfectPlayer<B> {
+impl<B: Game> Default for PerfectPlayer<B> {
     fn default() -> Self {
         Self::new()
     }
 }
 
-impl<B: GameBoard> PerfectPlayer<B> {
+impl<B: Game> PerfectPlayer<B> {
     pub fn new() -> Self {
         Self { best_move: None }
     }
 
     fn minmax(&mut self, board: &mut B, player: Player, depth: usize) -> Score {
-        if depth < 2 {
-            //print!("{board}{}| playing {player}: ", " ".repeat(depth));
+        if let Some(max_depth) = B::REASONABLE_SEARCH_DEPTH && depth >= max_depth {
+            return board.rate(player);
         }
+
         match board.result() {
             State::Winner(winner) => {
                 if winner == player {
@@ -83,8 +76,8 @@ impl<B: GameBoard> PerfectPlayer<B> {
     }
 }
 
-impl<G: Game> GamePlayer<G> for PerfectPlayer<G::Board> {
-    fn next_move(&mut self, board: &mut G::Board, this_player: Player) {
+impl<G: Game> GamePlayer<G> for PerfectPlayer<G> {
+    fn next_move(&mut self, board: &mut G, this_player: Player) {
         self.best_move = None;
         self.minmax(board, this_player, 0);
 

src/tic_tac_toe/board.rs

@@ -1,11 +1,11 @@
 use std::fmt::{Display, Write};
 
-use crate::{minmax::GameBoard, Player, State};
+use crate::{minmax::Score, Player, State, Game};
 
 #[derive(Clone)]
-pub struct Board(u32);
+pub struct TicTacToe(u32);
 
-impl Board {
+impl TicTacToe {
     pub fn empty() -> Self {
         // A = 1010
         // 18 bits - 9 * 2 bits - 4.5 nibbles
@@ -75,14 +75,14 @@ impl Board {
 }
 
 mod win_table {
-    use super::Board;
+    use super::TicTacToe;
     use crate::{Player, State};
 
     const WIN_TABLE_SIZE: usize = 2usize.pow(2 * 9);
     static WIN_TABLE: &[u8; WIN_TABLE_SIZE] =
         include_bytes!(concat!(env!("OUT_DIR"), "/win_table"));
 
-    pub fn result(board: &Board) -> State {
+    pub fn result(board: &TicTacToe) -> State {
         match WIN_TABLE[board.0 as usize] {
             0 => State::Winner(Player::X),
             1 => State::Winner(Player::X),
@@ -93,7 +93,7 @@ mod win_table {
     }
 }
 
-impl Display for Board {
+impl Display for TicTacToe {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         for i in 0..3 {
             for j in 0..3 {
@@ -113,9 +113,15 @@ impl Display for Board {
     }
 }
 
-impl GameBoard for Board {
+impl Game for TicTacToe {
     type Move = usize;
 
+    const REASONABLE_SEARCH_DEPTH: Option<usize> = None;
+
+    fn empty() -> Self {
+        Self::empty()
+    }
+
     fn possible_moves(&self) -> impl Iterator<Item = Self::Move> {
         debug_assert!(
             !self.iter().all(|x| x.is_some()),
@@ -129,7 +135,11 @@ impl GameBoard for Board {
     }
 
     fn result(&self) -> State {
-        Board::result(self)
+        TicTacToe::result(self)
+    }
+
+    fn rate(&self, _: Player) -> Score {
+        unimplemented!("we always finish the board")
     }
 
     fn make_move(&mut self, position: Self::Move, player: Player) {
@@ -143,11 +153,11 @@ impl GameBoard for Board {
 
 #[cfg(test)]
 mod tests {
-    use super::{Board, Player};
+    use super::{Player, TicTacToe};
 
     #[test]
     fn board_field() {
-        let mut board = Board::empty();
+        let mut board = TicTacToe::empty();
         board.set(0, None);
         board.set(8, Some(Player::X));
         board.set(4, Some(Player::O));

src/tic_tac_toe/game.rs

@@ -1,13 +1,17 @@
 use crate::{GamePlayer, Player, State};
 
-use super::{board::Board, TicTacToe};
+use super::TicTacToe;
 
-impl Board {
+impl TicTacToe {
     pub fn default_play<X: GamePlayer<TicTacToe>, O: GamePlayer<TicTacToe>>() -> Option<Player> {
         Self::empty().play(&mut X::default(), &mut O::default())
     }
 
-    pub fn play<A: GamePlayer<TicTacToe>, B: GamePlayer<TicTacToe>>(&mut self, x: &mut A, o: &mut B) -> Option<Player> {
+    pub fn play<A: GamePlayer<TicTacToe>, B: GamePlayer<TicTacToe>>(
+        &mut self,
+        x: &mut A,
+        o: &mut B,
+    ) -> Option<Player> {
         let mut current_player = Player::X;
 
         for _ in 0..9 {

src/tic_tac_toe/mod.rs

@@ -1,26 +1,17 @@
-use crate::Game;
-
 mod board;
 mod game;
 mod perfect;
 mod player;
 
-pub use {board::Board, perfect::PerfectPlayer, player::*};
-
-pub struct TicTacToe;
-
-impl Game for TicTacToe {
-    type Board = board::Board;
-}
+pub use {board::TicTacToe, perfect::PerfectPlayer, player::*};
 
 #[cfg(test)]
 mod tests {
-    use crate::{tic_tac_toe::board::Board, GamePlayer, Player};
+    use crate::{tic_tac_toe::board::TicTacToe, GamePlayer, Player};
 
     use super::{
         perfect::PerfectPlayer,
         player::{GreedyPlayer, RandomPlayer},
-        TicTacToe,
     };
 
     fn assert_win_ratio<X: GamePlayer<TicTacToe>, O: GamePlayer<TicTacToe>>(
@@ -30,7 +21,7 @@ mod tests {
         let mut results = [0u64, 0, 0];
 
         for _ in 0..runs {
-            let result = Board::default_play::<X, O>();
+            let result = TicTacToe::default_play::<X, O>();
             let idx = Player::as_u8(result);
             results[idx as usize] += 1;
         }

src/tic_tac_toe/perfect.rs

@@ -2,7 +2,7 @@ use std::ops::Neg;
 
 use crate::{GamePlayer, Player, State};
 
-use super::{board::Board, TicTacToe};
+use super::TicTacToe;
 
 #[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]
 enum Score {
@@ -41,7 +41,7 @@ impl PerfectPlayer {
         }
     }
 
-    fn minmax(&mut self, board: &mut Board, player: Player, depth: usize) -> Score {
+    fn minmax(&mut self, board: &mut TicTacToe, player: Player, depth: usize) -> Score {
         if depth < 2 {
             //print!("{board}{}| playing {player}: ", " ".repeat(depth));
         }
@@ -105,7 +105,7 @@ impl PerfectPlayer {
 }
 
 impl GamePlayer<TicTacToe> for PerfectPlayer {
-    fn next_move(&mut self, board: &mut Board, this_player: Player) {
+    fn next_move(&mut self, board: &mut TicTacToe, this_player: Player) {
         self.best_move = usize::MAX;
         self.minmax(board, this_player, 0);
 

src/tic_tac_toe/player.rs

@@ -2,13 +2,13 @@ use std::io::Write;
 
 use crate::{GamePlayer, Player};
 
-use super::{board::Board, TicTacToe};
+use super::TicTacToe;
 
 #[derive(Clone, Default)]
 pub struct GreedyPlayer;
 
 impl GamePlayer<TicTacToe> for GreedyPlayer {
-    fn next_move(&mut self, board: &mut Board, this_player: Player) {
+    fn next_move(&mut self, board: &mut TicTacToe, this_player: Player) {
         let first_free = board.iter().position(|p| p.is_none()).unwrap();
         board.set(first_free, Some(this_player));
     }
@@ -18,7 +18,7 @@ impl GamePlayer<TicTacToe> for GreedyPlayer {
 pub struct HumanPlayer;
 
 impl GamePlayer<TicTacToe> for HumanPlayer {
-    fn next_move(&mut self, board: &mut Board, this_player: Player) {
+    fn next_move(&mut self, board: &mut TicTacToe, this_player: Player) {
         loop {
             print!("{board}where to put the next {this_player}? (0-8): ");
 
@@ -55,7 +55,7 @@ fn fun_random() -> u64 {
 }
 
 impl GamePlayer<TicTacToe> for RandomPlayer {
-    fn next_move(&mut self, board: &mut Board, this_player: Player) {
+    fn next_move(&mut self, board: &mut TicTacToe, this_player: Player) {
         loop {
             let next = (fun_random() % 9) as usize;
             match board.get(next) {