diff --git a/Cargo.lock b/Cargo.lock
index 698d7af..d7404b8 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -152,6 +152,7 @@ dependencies = [
 name = "othello"
 version = "0.1.0"
 dependencies = [
+ "either",
  "num",
  "rand",
  "rayon",
diff --git a/Cargo.toml b/Cargo.toml
index b00ab1d..a29ee79 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -8,6 +8,7 @@ edition = "2021"
 debug = true
 
 [dependencies]
+either = "1.13.0"
 num = "0.4"
 rand = "0.9"
 rayon = "1.10"
diff --git a/src/board.rs b/src/board.rs
index 1ce912f..ee96cc4 100644
--- a/src/board.rs
+++ b/src/board.rs
@@ -151,7 +151,7 @@ impl Board {
         chains.extend(j_chain.map(|range| range.into_iter().map(|j| (i, j)).collect()));
 
         // handle diagonals
-        chains.extend(diag(i, j, 0, 0, BOARD_SIZE - 1, BOARD_SIZE - 1));
+        chains.extend(diag(i, j, 0, 0, BOARD_SIZE - 1, BOARD_SIZE - 1).map(Iterator::collect));
 
         let mut fill: Vec<(usize, usize)> = Vec::with_capacity(chains.iter().map(Vec::len).sum());
 
diff --git a/src/complexagent.rs b/src/complexagent.rs
index 9803a98..8fe81e2 100644
--- a/src/complexagent.rs
+++ b/src/complexagent.rs
@@ -248,7 +248,7 @@ pub struct ComplexAgent {
 
 impl ComplexAgent {
     pub fn new(color: Piece) -> Self {
-        const MAX_DEPTH: usize = 6;
+        const MAX_DEPTH: usize = 7;
         Self {
             color,
             future_moves: FutureMoves::new(color, MAX_DEPTH),
diff --git a/src/misc.rs b/src/misc.rs
index 3f6cbe7..147efff 100644
--- a/src/misc.rs
+++ b/src/misc.rs
@@ -1,31 +1,38 @@
+use either::Either;
 use std::{iter::Rev, ops::RangeInclusive};
 
-pub fn split_from<T>(min: T, max: T, x: T) -> [Vec<T>; 2]
+pub fn split_from<T>(min: T, max: T, x: T) -> [impl Iterator<Item = T> + Clone; 2]
 where
     T: num::Integer + Copy,
     RangeInclusive<T>: Iterator<Item = T> + DoubleEndedIterator,
     Rev<RangeInclusive<T>>: Iterator<Item = T>,
 {
-    // check that x is in range
-    if min > x || x > max {
-        return [const { Vec::new() }; 2];
-    }
+    let in_range = (x >= min) && (x <= max);
 
+    // RangeInclusive (1..=0), has 0 elements
+    let base = Either::Right(T::one()..=T::zero());
     [
-        if x > min + T::one() {
-            (min..=(x - T::one())).rev().collect()
+        if in_range && x > min + T::one() {
+            Either::Left((min..=(x - T::one())).rev())
         } else {
-            Vec::new()
+            base.clone()
         },
-        if x + T::one() < max {
-            ((x + T::one())..=max).collect()
+        if in_range && x + T::one() < max {
+            Either::Right((x + T::one())..=max)
         } else {
-            Vec::new()
+            base
         },
     ]
 }
 
-pub fn diag<T>(i: T, j: T, min_i: T, min_j: T, max_i: T, max_j: T) -> [Vec<(T, T)>; 4]
+pub fn diag<T>(
+    i: T,
+    j: T,
+    min_i: T,
+    min_j: T,
+    max_i: T,
+    max_j: T,
+) -> [impl Iterator<Item = (T, T)>; 4]
 where
     T: num::Integer + Copy,
     RangeInclusive<T>: Iterator<Item = T> + DoubleEndedIterator,
@@ -34,13 +41,7 @@ where
     let i_chains = split_from(min_i, max_i, i);
     let j_chains = split_from(min_j, max_j, j);
 
-    [(0, 0), (1, 1), (1, 0), (0, 1)].map(|(a, b)| {
-        i_chains[a]
-            .iter()
-            .cloned()
-            .zip(j_chains[b].clone())
-            .collect()
-    })
+    [(0, 0), (1, 1), (1, 0), (0, 1)].map(|(a, b)| i_chains[a].clone().zip(j_chains[b].clone()))
 }
 
 #[cfg(test)]
@@ -49,15 +50,24 @@ mod test {
 
     #[test]
     fn split_test() {
-        assert_eq!(split_from(0, 6, 2), [vec![1, 0], vec![3, 4, 5, 6]]);
+        assert_eq!(
+            split_from(0, 6, 2).map(Iterator::collect::<Vec<usize>>),
+            [vec![1, 0], vec![3, 4, 5, 6]]
+        );
 
-        assert_eq!(split_from(0, 6, 0), [vec![], vec![1, 2, 3, 4, 5, 6]]);
+        assert_eq!(
+            split_from(0, 6, 0).map(Iterator::collect::<Vec<usize>>),
+            [vec![], vec![1, 2, 3, 4, 5, 6]]
+        );
 
-        assert_eq!(split_from(0, 6, 6), [vec![5, 4, 3, 2, 1, 0], vec![]]);
+        assert_eq!(
+            split_from(0, 6, 6).map(Iterator::collect::<Vec<usize>>),
+            [vec![5, 4, 3, 2, 1, 0], vec![]]
+        );
 
         // test out-of-bounds and also generics
         assert_eq!(
-            split_from::<i16>(-1i16, 4i16, 10i16),
+            split_from::<i16>(-1i16, 4i16, 10i16).map(Iterator::collect::<Vec<i16>>),
             [const { Vec::new() }; 2]
         );
     }
@@ -65,7 +75,7 @@ mod test {
     #[test]
     fn diag_test() {
         assert_eq!(
-            diag(2, 3, 0, 0, 7, 7),
+            diag(2, 3, 0, 0, 7, 7).map(Iterator::collect::<Vec<(usize, usize)>>),
             [
                 vec![(1, 2), (0, 1)],
                 vec![(3, 4), (4, 5), (5, 6), (6, 7)],