7 files changed, 12 insertions, 11 deletions
diff --git a/mdpoly/abc.py b/mdpoly/abc.py
index 811910b..0a2e783 100644
--- a/mdpoly/abc.py
+++ b/mdpoly/abc.py
@@ -1,6 +1,6 @@
 """ Abstract Base Classes of MDPoly """
 
-from .types import Number, Shape, MatrixIndex, PolyIndex
+from .index import Number, Shape, MatrixIndex, PolyIndex
 from .constants import NUMERICS_EPS
 from .util import iszero
 
diff --git a/mdpoly/algebra.py b/mdpoly/algebra.py
index abd15d5..a07c4d6 100644
--- a/mdpoly/algebra.py
+++ b/mdpoly/algebra.py
@@ -4,7 +4,7 @@ from .abc import Leaf, Expr, Repr
 from .leaves import Nothing, Const, Param, Var
 from .errors import AlgebraicError, InvalidShape
 from .state import State
-from .types import Shape, MatrixIndex, PolyIndex
+from .index import Shape, MatrixIndex, PolyIndex
 from .representations import HasRepr
 
 from typing import Protocol, Self, Any, runtime_checkable
diff --git a/mdpoly/types.py b/mdpoly/index.py
index 9e4ecb7..2837a46 100644
--- a/mdpoly/types.py
+++ b/mdpoly/index.py
@@ -13,11 +13,6 @@ if TYPE_CHECKING:
 Number = int | float
 
 
-def filtertype(t: type, seq: Iterable):
-    """ Filter based on type. """
-    yield from filter(lambda x: isinstance(x, t), seq)
-
-
 class Shape(NamedTuple):
     """ Describes the shape of a mathematical object. """
     rows: int
diff --git a/mdpoly/leaves.py b/mdpoly/leaves.py
index dbfd332..af43435 100644
--- a/mdpoly/leaves.py
+++ b/mdpoly/leaves.py
@@ -1,5 +1,5 @@
 from .abc import Leaf, Repr
-from .types import Number, Shape, MatrixIndex, PolyVarIndex, PolyIndex
+from .index import Number, Shape, MatrixIndex, PolyVarIndex, PolyIndex
 from .state import State
 from .errors import MissingParameters
 from .representations import HasRepr
diff --git a/mdpoly/representations.py b/mdpoly/representations.py
index b7943ad..b541c3e 100644
--- a/mdpoly/representations.py
+++ b/mdpoly/representations.py
@@ -1,5 +1,5 @@
 from .abc import Repr 
-from .types import Number, Shape, MatrixIndex, PolyIndex
+from .index import Number, Shape, MatrixIndex, PolyIndex
 from .state import State
 
 from typing import Protocol, Iterable
diff --git a/mdpoly/state.py b/mdpoly/state.py
index 70fca24..e0a6bc5 100644
--- a/mdpoly/state.py
+++ b/mdpoly/state.py
@@ -2,10 +2,10 @@ from __future__ import annotations
 from typing import TYPE_CHECKING
 from dataclasses import dataclass, field
 
-from .types import PolyVarIndex
+from .index import PolyVarIndex
 
 if TYPE_CHECKING:
-    from .types import Number
+    from .index import Number
     from .leaves import Var, Param, Const
 
 
diff --git a/mdpoly/util.py b/mdpoly/util.py
index 937e7d4..c7f3b51 100644
--- a/mdpoly/util.py
+++ b/mdpoly/util.py
@@ -1,6 +1,7 @@
 from .constants import NUMERICS_EPS
 
 from itertools import tee, filterfalse
+from typing import Iterable
 
 def partition(pred, iterable):
     """Partition entries into false entries and true entries.
@@ -30,3 +31,8 @@ def iszero(x: float, eps: float =NUMERICS_EPS) -> bool:
     ``eps`` or the default value at :py:data:`mdpoly.constants.NUMERICS_EPS`.
     """
     return isclose(x, 0.)
+
+
+def filtertype(t: type, seq: Iterable):
+    """ Filter based on type. """
+    yield from filter(lambda x: isinstance(x, t), seq)