Simplify 'BitboardIterator'

src/board/bitboard/iterator.rs

@@ -2,11 +2,11 @@
 /// [Bitboard].
 use crate::board::Bitboard;
 
-pub struct BitboardIterator(u64);
+pub struct BitboardIterator(Bitboard);
 
 impl BitboardIterator {
     pub fn new(board: Bitboard) -> Self {
-        Self(board.0)
+        Self(board)
     }
 }
 
@@ -14,17 +14,15 @@ impl Iterator for BitboardIterator {
     type Item = crate::board::Square;
 
     fn next(&mut self) -> Option<Self::Item> {
-        if self.0 == 0 {
-            None
-        } else {
-            let lsb = self.0.trailing_zeros() as usize;
-            self.0 ^= 1 << lsb;
-            Some(crate::board::Square::from_index(lsb))
-        }
+        let res = self.0.any_square();
+        if let Some(square) = res {
+            self.0 ^= square;
+        };
+        res
     }
 
     fn size_hint(&self) -> (usize, Option<usize>) {
-        let size = self.0.count_ones() as usize;
+        let size = self.0.count() as usize;
 
         (size, Some(size))
     }

src/board/bitboard/mod.rs

@@ -75,6 +75,12 @@ impl Bitboard {
         (self.0 & (self.0.wrapping_sub(1))) != 0
     }
 
+    /// Return a [Square] from the board, or `None` if it is empty.
+    #[inline(always)]
+    pub fn any_square(self) -> Option<Square> {
+        Square::try_from_index(self.0.trailing_zeros() as usize)
+    }
+
     /// Iterate over the power-set of a given [Bitboard], yielding each possible sub-set of
     /// [Square] that belong to the [Bitboard]. In other words, generate all set of [Square] that
     /// contain all, some, or none of the [Square] that are in the given [Bitboard].
@@ -110,12 +116,10 @@ impl TryInto<Square> for Bitboard {
     type Error = IntoSquareError;
 
     fn try_into(self) -> Result<Square, Self::Error> {
-        let index = match self.count() {
-            1 => self.0.trailing_zeros() as usize,
-            0 => return Err(IntoSquareError::EmptyBoard),
-            _ => return Err(IntoSquareError::TooManySquares),
-        };
-        Ok(Square::from_index(index))
+        if self.has_more_than_one() {
+            return Err(IntoSquareError::TooManySquares);
+        }
+        self.any_square().ok_or(IntoSquareError::EmptyBoard)
     }
 }
 
@@ -479,6 +483,23 @@ mod test {
         );
     }
 
+    #[test]
+    fn any_square() {
+        for square in Square::iter() {
+            assert_eq!(square.into_bitboard().any_square(), Some(square));
+        }
+    }
+
+    #[test]
+    fn any_square_empty() {
+        assert!(Bitboard::EMPTY.any_square().is_none());
+    }
+
+    #[test]
+    fn any_square_full_board() {
+        assert!(Bitboard::ALL.any_square().is_some());
+    }
+
     #[test]
     fn into_square() {
         for square in Square::iter() {