From 7e10cab22cd0cd20ff48bf5665f0f7536f1ad032 Mon Sep 17 00:00:00 2001
From: Carl Worth <cworth@cworth.org>
Date: Fri, 24 Apr 2020 14:27:24 -0700
Subject: [PATCH] Add a new dvonn_board_cell_owned_by function
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The compiler was warning that we were comparing enums of two different
types. That's true—we are, but that's because the values for
dvonn_cell_t are declared by reference to dvonn_player_t values.

Anyway, rather than cluttering up the code with lots of casts to
silence this warning, here we add a new function that takes care of
that cast, leading to more readable code.
---
 dvonn-board.c | 15 ++++++++++++++-
 dvonn-board.h |  7 +++++++
 dvonn.c       |  2 +-
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/dvonn-board.c b/dvonn-board.c
index f8f9b93..eeab830 100644
--- a/dvonn-board.c
+++ b/dvonn-board.c
@@ -101,6 +101,19 @@ dvonn_board_cell_occupied (dvonn_board_t *board,
     return TRUE;
 }
 
+dvonn_bool_t
+dvonn_board_cell_owned_by (dvonn_board_t *board,
+			   int x, int y,
+			   dvonn_player_t player)
+{
+    if (! dvonn_board_cell_occupied (board, x, y))
+	return FALSE;
+
+    /* Cast here to avoid compiler warning about mixing enum types in
+     * a comparison. */
+    return board->cells[x][y].type == (dvonn_cell_type_t) player;
+}
+
 dvonn_bool_t
 dvonn_board_cell_surrounded (dvonn_board_t *board,
 			     int x, int y)
@@ -152,7 +165,7 @@ dvonn_board_move_legal (dvonn_board_t *board,
 	return FALSE;
     }
 
-    if (board->cells[x1][y1].type != board->player) {
+    if (! dvonn_board_cell_owned_by (board, x1, y1, board->player)) {
 	*error = "You cannot move your opponent's stack";
 	return FALSE;
     }
diff --git a/dvonn-board.h b/dvonn-board.h
index 7a361c3..7192301 100644
--- a/dvonn-board.h
+++ b/dvonn-board.h
@@ -100,6 +100,13 @@ dvonn_bool_t
 dvonn_board_cell_occupied (dvonn_board_t *board,
 			   int x, int y);
 
+/* Is the cell at (x,y) occupied by a piece (or stack) with the given
+ * player's piece at the top. Returns FALSE for all out-of-bounds
+ * coordinates. */
+dvonn_bool_t
+dvonn_board_cell_owned_by (dvonn_board_t *board,
+			   int x, int y, dvonn_player_t player);
+
 /* Is the cell at (x,y) surrounded by other pieces, (such that it is
  * not legal for a piece at (x,y) to move. */
 dvonn_bool_t
diff --git a/dvonn.c b/dvonn.c
index 709d12a..99cadf7 100644
--- a/dvonn.c
+++ b/dvonn.c
@@ -212,7 +212,7 @@ on_button_press_event (GtkWidget	*widget,
     }
 
     if (! game->has_selected) {
-	if (game->board.cells[x][y].type == game->board.player &&
+	if (dvonn_board_cell_owned_by (&game->board, x, y, game->board.player) &&
 	    ! dvonn_board_cell_surrounded (&game->board, x, y))
 	    {
 		    game->has_selected = TRUE;
-- 
2.43.0