2 files changed, 11 insertions, 5 deletions
diff --git a/src/board/mod.rs b/src/board/mod.rs
index 39248eb..1e4fd93 100644
--- a/src/board/mod.rs
+++ b/src/board/mod.rs
@@ -1,6 +1,6 @@
 use crate::{bitboard::{Bitboard, BitboardFns}, moves::{Move, MoveKind}, attacks::Attacks, square::Square, board::io::IO, clock::Clock};
 
-use self::{zobrist::{ZobristSeed, Zobrist}, piece::Piece, color::Color};
+use self::{zobrist::{ZobristSeed, Zobrist, ZobristHash}, piece::Piece, color::Color};
 pub mod io;
 pub mod color;
 pub mod piece;
@@ -27,12 +27,12 @@ pub struct Board {
     pub clock: Clock,
 
     /// List of all positions to determine repetitions
-    pub positions: Vec<u64>,
+    pub positions: Vec<ZobristHash>,
 
     // Computed values
     pub occupancy: Bitboard,
     /// Zobrist hash of the current position
-    pub hash: u64,
+    pub hash: ZobristHash,
     zobrist_seed: ZobristSeed,
 
 
@@ -256,7 +256,7 @@ impl Board {
         captured_piece: Option<Piece>,
         previous_ep_target: Option<Square>,
         previous_castling_rights: [[bool; 2]; 2],
-        previous_hash: u64,
+        previous_hash: ZobristHash,
     ) {
         let move_source_bb = mov.source.to_bitboard();
         let move_target_bb = mov.target.to_bitboard();
@@ -388,6 +388,10 @@ impl Board {
         let square = king_bb.bitscan();
         self.is_square_attacked(square, color.flip())
     }
+
+    pub fn threefold_repetition(&self) -> bool {
+        self.positions.iter().filter(|&&p| p == self.hash).count() >= 3
+    }
 }
 
 
diff --git a/src/board/zobrist.rs b/src/board/zobrist.rs
index 88a2fb7..251f333 100644
--- a/src/board/zobrist.rs
+++ b/src/board/zobrist.rs
@@ -11,7 +11,9 @@ const TOTAL_FILES:           usize = 8;
 const TOTAL_CASTLING_RIGHTS: usize = 4;
 const ZOBRIST_SEED_SIZE:     usize = TOTAL_SQUARES * TOTAL_PIECES + TOTAL_CASTLING_RIGHTS + TOTAL_FILES + 1;
 
-pub type ZobristSeed = [u64; ZOBRIST_SEED_SIZE];
+pub type ZobristHash = u64;
+
+pub type ZobristSeed = [ZobristHash; ZOBRIST_SEED_SIZE];
 
 pub trait Zobrist {
     fn seed() -> ZobristSeed;