[position] Print the chess board diagram with box drawing characters

position/src/position/diagram_formatter.rs

@@ -14,23 +14,23 @@ impl<'a> DiagramFormatter<'a> {
 
 impl<'a> fmt::Display for DiagramFormatter<'a> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "  +-----------------+\n")?;
+        write!(f, "  ╔═════════════════╗\n")?;
 
         for rank in Rank::ALL.iter().rev() {
-            write!(f, "{rank} | ")?;
+            write!(f, "{rank} ║ ")?;
 
             for file in File::ALL.iter() {
                 let square = Square::from_file_rank(*file, *rank);
                 match self.0.piece_on_square(square) {
                     Some(placed_piece) => write!(f, "{} ", placed_piece.piece())?,
-                    None => write!(f, ". ")?,
+                    None => write!(f, "· ")?,
                 }
             }
 
-            write!(f, "|\n")?;
+            write!(f, "║\n")?;
         }
 
-        write!(f, "  +-----------------+\n")?;
+        write!(f, "  ╚═════════════════╝\n")?;
         write!(f, "    a b c d e f g h\n")?;
 
         Ok(())