actually add threat.h

Threat.h

@@ -0,0 +1,42 @@
+#ifndef __THREAT_H_INC
+#define __THREAT_H_INC
+
+namespace Threat {
+	byte can_capture(byte square) {
+		// TODO make this more efficient
+		byte t = 0;
+		Board::swap_side();
+		Movegen gen = Movegen();
+		Move m;
+		while((m = gen.next_move()).sq_to != 255) {
+			if(m.sq_to == square) {
+				t++;
+			}
+		}
+		Board::swap_side();
+		return t;
+	}
+
+	byte threats(byte square) {
+		byte t = 0;
+		Board::swap_side();
+		t = can_capture(square);
+		Board::swap_side();
+		return t;
+	}
+
+	bool is_check() {
+		byte king_ptr = Board::field[PTR_W_KING | Board::black_moving()];
+		return (threats(king_ptr)) > 0;
+	}
+	
+	bool illegal() {
+		// if the enemy king can be captured, move they did is illegal.
+		byte king_ptr = Board::field[PTR_W_KING | !Board::black_moving()];
+		return (can_capture(king_ptr)) > 0;
+
+	}
+	
+}
+
+#endif