Implement board state read functions

board.c

@@ -87,3 +87,49 @@ board_unmark (
     elem->potential &= (1 << value) ^ 0x1FF;
   }
 }
+
+
+bool
+board_has_value (
+  struct board *board,
+  board_pos x,
+  board_pos y
+)
+{
+  if (is_in_bounds (x, y))
+  {
+    return BOARD_ELEM (board, x, y)->has_value;
+  }
+  return false;
+}
+
+
+element_value
+board_get_value (
+  struct board *board,
+  board_pos x,
+  board_pos y
+)
+{
+  if (is_in_bounds (x, y))
+  {
+    return BOARD_ELEM (board, x, y)->value;
+  }
+  return 0;
+}
+
+
+bool
+board_is_marked (
+  struct board *board,
+  board_pos x,
+  board_pos y,
+  element_value value
+)
+{
+  if (is_in_bounds (x, y) && is_valid_value (value))
+  {
+    return BOARD_ELEM (board, x, y)->potential & (1 << value);
+  }
+  return false;
+}

board.h

@@ -83,3 +83,41 @@ board_unmark (
   board_pos y,
   element_value value
 );
+
+
+/**
+ * Get whether or not an element has a decided value
+ */
+bool
+board_has_value (
+  struct board *board,
+  board_pos x,
+  board_pos y
+);
+
+
+/**
+ * Get definite value of a board element
+ *
+ * NOTE: Getting the definite value of an element without a value is undefined
+ */
+element_value
+board_get_value (
+  struct board *board,
+  board_pos x,
+  board_pos y
+);
+
+
+/**
+ * Get whether or not a board element is marked with a particular value
+ *
+ * NOTE: Getting the mark state of an element with a value is undefined
+ */
+bool
+board_is_marked (
+  struct board *board,
+  board_pos x,
+  board_pos y,
+  element_value value
+);