add convenience into_mirrored method

src/board.rs

@@ -368,13 +368,23 @@ impl Board {
         self.by_color.swap();
     }
 
+    pub fn into_swapped_colors(mut self) -> Board {
+        self.swap_colors();
+        self
+    }
+
     /// Mirror the board vertically and swap piece colors, so that the resulting
     /// board is equivalent modulo color.
     pub fn mirror(&mut self) {
         self.flip_vertical();
         self.swap_colors();
     }
 
+    pub fn into_mirrored(mut self) -> Board {
+        self.mirror();
+        self
+    }
+
     pub fn pop_front(&mut self) -> Option<(Square, Piece)> {
         self.occupied
             .first()

src/setup.rs

@@ -117,6 +117,11 @@ impl Setup {
         self.ep_square = None;
     }
 
+    pub fn into_swapped_turn(mut self) -> Setup {
+        self.swap_turn();
+        self
+    }
+
     /// Mirror vertically and swap turns and all piece colors, so that the
     /// resulting setup is equivalent modulo color.
     ///
@@ -135,6 +140,11 @@ impl Setup {
         }
     }
 
+    pub fn into_mirrored(mut self) -> Setup {
+        self.mirror();
+        self
+    }
+
     pub fn position<P: FromSetup>(self, mode: CastlingMode) -> Result<P, PositionError<P>> {
         P::from_setup(self, mode)
     }