chore: stuff

games/src/interface/bitboard.rs

@@ -1,5 +1,6 @@
 use super::{
-    CartesianFile, CartesianRank, CartesianSquare, RepresentableType, SetType,
+    derive_set, CartesianFile, CartesianRank, CartesianSquare,
+    RepresentableType, SetType,
 };
 
 #[derive(
@@ -24,9 +25,9 @@ pub struct CartesianSquareSet<const F: u8, const R: u8>(u64);
 
 impl<const F: u8, const R: u8> CartesianSquareSet<F, R> {
     /// The BitBoard containing Squares in the first File.
-    const FIRST_FILE: Self = Self(0);
+    const FIRST_FILE: Self = derive_set!(@first_file u64 F R);
     /// The BitBoard containing Squares in the first Rank.
-    const FIRST_RANK: Self = Self(0);
+    const FIRST_RANK: Self = derive_set!(@first_rank u64 F R);
 
     /// north returns a new Self with all the squares shifted to the north.
     #[must_use]
@@ -68,7 +69,7 @@ impl<const F: u8, const R: u8> CartesianSquareSet<F, R> {
 impl<const F: u8, const R: u8> SetType<u64, CartesianSquare<F, R>, u8>
     for CartesianSquareSet<F, R>
 {
-    const EMPTY: Self = Self(0);
+    const EMPTY: Self = derive_set!(@universe_bb u64 F R);
     const UNIVERSE: Self = Self(0);
 }
 

games/src/interface/mod.rs

@@ -593,8 +593,7 @@ pub(crate) use set_type;
 
 // derive_set resolves into some of the fundamental sets for a SetType/BitBoard.
 macro_rules! derive_set {
-    // @universe resolves into the universal set.
-    (@universe $base:tt $elem:tt) => {{
+    (@universe $base:tt $elem:path) => {{
         use $crate::interface::RepresentableType;
         Self(
             // (1 << Square::N) - 1
@@ -607,37 +606,42 @@ macro_rules! derive_set {
         )
     }};
 
+    // @universe resolves into the universal set.
+    (@universe_bb $base:ident $F:ident $R:ident) => {{
+        Self(
+            // (1 << Square::N) - 1
+            match (1 as $base).checked_shl($F as u32 * $R as u32) {
+                Some(universe) => universe.wrapping_sub(1),
+                None => (-1i8) as $base,
+            },
+        )
+    }};
+
     // @first_rank resolves into the set containing the Squares in the first Rank.
-    (@first_rank $bb:tt) => {{
-        use $crate::interface::{RepresentableType, BitBoardType, SquareType};
+    (@first_rank $base:ident $F:ident $R:ident) => {{
         Self(
             // (1 << File::N) - 1
-            match (1 as <$bb as BitBoardType>::Base)
-                .checked_shl(<<<$bb as BitBoardType>::Square as SquareType>::File as RepresentableType<u8>>::N as u32) {
-                    Some(universe) => universe.wrapping_sub(1),
-                    None => 1,
-                }
+            match (1 as $base).checked_shl($F as u32) {
+                Some(universe) => universe.wrapping_sub(1),
+                None => 1,
+            },
         )
     }};
 
     // @first_file resolves into the set containing the Squares in the first File.
-    (@first_file $bb:tt) => {{
-        use $crate::interface::{RepresentableType, BitBoardType, SquareType};
-
+    (@first_file $base:ident $F:ident $R:ident) => {{
         let mut i = 0u32;
-        let mut file = 0 as <$bb as BitBoardType>::Base;
-        let file_n = <<
-            <$bb as BitBoardType>::Square as SquareType
-        >::File as RepresentableType<u8>>::N as u32;
+        let mut file = 0 as $base;
+        let file_n = $F as u32;
 
         loop {
             // i < file_n
             if i >= file_n {
-                break
+                break;
             }
 
             // file |= 1 << (File::N * i)
-            file |= match (1 as <$bb as BitBoardType>::Base).checked_shl(file_n * i) {
+            file |= match (1 as $base).checked_shl(file_n * i) {
                 Some(file) => file,
                 None => 0,
             };

games/src/interface/square.rs

@@ -258,8 +258,8 @@ impl<const C: u8> Iterator for CartesianFile<C> {
 impl<const C: u8> DoubleEndedIterator for CartesianFile<C> {
     fn next_back(&mut self) -> Option<Self::Item> {
         let idx = (*self).into();
-        self.0 = idx - 1;
-        if idx < C {
+        if idx > 0 {
+            self.0 = idx - 1;
             Some(Self(idx))
         } else {
             None
@@ -347,8 +347,8 @@ impl<const C: u8> Iterator for CartesianRank<C> {
 impl<const C: u8> DoubleEndedIterator for CartesianRank<C> {
     fn next_back(&mut self) -> Option<Self::Item> {
         let idx = (*self).into();
-        self.0 = idx - 1;
-        if idx < C {
+        if idx > 0 {
+            self.0 = idx - 1;
             Some(Self(idx))
         } else {
             None