Added a minimax evaluation function

1 files changed, 25 insertions, 0 deletions

diff --git a/ai/src/lib.rs b/ai/src/lib.rs
index 4e22708..c5b60f0 100644
--- a/ai/src/lib.rs
+++ b/ai/src/lib.rs
@@ -1,3 +1,5 @@
+use std::f32::NEG_INFINITY;
+
 pub use model::{CheckersBitBoard, Move, PieceColor, PossibleMoves};
 
 const KING_WORTH: u32 = 2;
@@ -25,3 +27,26 @@ fn eval_position(board: CheckersBitBoard) -> f32 {
 		0.0
 	}
 }
+
+fn eval(depth: usize, board: CheckersBitBoard) -> f32 {
+	if depth == 0 {
+		eval_position(board)
+	} else {
+		let turn = board.turn();
+		let mut best_eval = -NEG_INFINITY;
+		for current_move in PossibleMoves::moves(board) {
+			let board = unsafe {current_move.apply_to(board)};
+			let current_eval = if board.turn() != turn {
+				-eval(depth - 1, board)
+			} else {
+				eval(depth - 1, board)
+			};
+
+			if best_eval < current_eval {
+				best_eval = current_eval;
+			}
+		}
+
+		best_eval
+	}
+}
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