diff --git a/test/lin_rec.py b/test/lin_rec.py
index ae810d85..98ccc619 100644
--- a/test/lin_rec.py
+++ b/test/lin_rec.py
@@ -374,7 +374,7 @@ def run(self, sim_lim: int) -> Self:  # no-cover
         while cycle < sim_lim:
             steps_reset = 2 * step
 
-            leftmost = rightmost = init_pos = tape.head
+            leftmost = rightmost = tape.head
 
             init_state = state
 
@@ -423,12 +423,7 @@ def run(self, sim_lim: int) -> Self:  # no-cover
                 if tape.scan != init_tape.scan:
                     continue
 
-                if tape.aligns_with(
-                        init_tape,
-                        curr - init_pos,
-                        leftmost,
-                        rightmost,
-                ):
+                if tape.aligns_with(init_tape, leftmost, rightmost):
                     self.infrul = step
                     break
 
diff --git a/tm/machine.py b/tm/machine.py
index 8d5edf17..56dbbf27 100644
--- a/tm/machine.py
+++ b/tm/machine.py
@@ -274,7 +274,7 @@ def quick_term_or_rec(prog: str, sim_lim: int) -> bool:
     while cycle < sim_lim:
         steps_reset = 2 * step
 
-        leftmost = rightmost = init_pos = tape.head
+        leftmost = rightmost = tape.head
 
         init_state = state
 
@@ -309,12 +309,7 @@ def quick_term_or_rec(prog: str, sim_lim: int) -> bool:
             if tape.scan != init_tape.scan:
                 continue
 
-            if tape.aligns_with(
-                    init_tape,
-                    curr - init_pos,
-                    leftmost,
-                    rightmost,
-            ):
+            if tape.aligns_with(init_tape, leftmost, rightmost):
                 return True
 
     return False
diff --git a/tm/reason.py b/tm/reason.py
index 931aeda6..853e7d78 100644
--- a/tm/reason.py
+++ b/tm/reason.py
@@ -287,8 +287,7 @@ def __iter__(self) -> Iterator[History]:
             prev = prev.prev
 
     def check_rec(self) -> bool:
-        curr_head = self.head
-        assert curr_head is not None
+        assert (curr_head := self.head) is not None
 
         leftmost = rightmost = curr_head
 
@@ -299,8 +298,7 @@ def check_rec(self) -> bool:
             if self.state != prev.state or self.scan != prev.scan:
                 continue
 
-            prev_head = prev.head
-            assert prev_head is not None
+            assert (prev_head := prev.head) is not None
 
             if prev_head < leftmost:
                 leftmost = prev_head
@@ -310,12 +308,7 @@ def check_rec(self) -> bool:
             prev_tape = prev.tape
             assert prev_tape is not None
 
-            if curr_tape.aligns_with(
-                    prev_tape,
-                    curr_head - prev_head,
-                    leftmost,
-                    rightmost,
-            ):
+            if curr_tape.aligns_with(prev_tape, leftmost, rightmost):
                 return True
 
         return False
diff --git a/tm/tape.py b/tm/tape.py
index a79c7aa0..92ff7c0f 100644
--- a/tm/tape.py
+++ b/tm/tape.py
@@ -678,11 +678,10 @@ def get_cnt(self, start: int, stop: int) -> TapeSlice:
     def aligns_with(
             self,
             prev: HeadTape,
-            diff: int,
             leftmost: int,
             rightmost: int,
     ) -> bool:
-        if 0 < diff:
+        if 0 < (diff := self.head - prev.head):
             slice1 = prev.get_ltr(leftmost)
             slice2 = self.get_ltr(leftmost + diff)