From 6564361e510d8ee78f39f7e6e85b9da4cf13e8b9 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 3 Dec 2025 19:43:28 +0000
Subject: [PATCH 1/2] Initial plan


From 4e03643587e500c26f6b00a60a6eb447ff3ab07c Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 3 Dec 2025 19:50:22 +0000
Subject: [PATCH 2/2] Address PR review comments: trailing whitespace,
 validation, docstring, grammar, unused variable

Co-authored-by: skilledwolf <18141588+skilledwolf@users.noreply.github.com>
---
 README.md                                     |  2 +-
 pyproject.toml                                |  2 +-
 src/quantumhall_matrixelements/__init__.py    | 13 +++++-----
 src/quantumhall_matrixelements/diagnostic.py  |  8 +++----
 .../exchange_hankel.py                        | 10 ++++----
 .../exchange_legendre.py                      | 15 +++++-------
 src/quantumhall_matrixelements/planewave.py   | 24 ++++++++++---------
 tests/test_exchange_legendre.py               |  4 +++-
 tests/test_validation.py                      |  4 +++-
 9 files changed, 43 insertions(+), 39 deletions(-)

diff --git a/README.md b/README.md
index d1f0ea0..3a4617c 100644
--- a/README.md
+++ b/README.md
@@ -135,7 +135,7 @@ The package provides two backends for computing exchange kernels:
    - **Recommended for**: Reference calculations and verifying the Gauss–Legendre backend.
 
 ## Notes
-The following wavefunction used to find all matrix elements:
+The following wavefunction is used to find all matrix elements:
 
 $$
 \Psi_{nX}^\sigma(x,y)
diff --git a/pyproject.toml b/pyproject.toml
index aa2a12f..ff312f5 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -7,7 +7,7 @@ name = "quantumhall_matrixelements"
 description = "Landau-level plane-wave form factors and exchange kernels for quantum Hall systems."
 readme = "README.md"
 authors = [
-  { name = "Tobias Wolf", email = "public@wolft.xyz" }, 
+  { name = "Tobias Wolf", email = "public@wolft.xyz" },
   { name = "Sparsh Mishra" }
 ]
 license = { text = "MIT" }
diff --git a/src/quantumhall_matrixelements/__init__.py b/src/quantumhall_matrixelements/__init__.py
index 8617950..6243285 100644
--- a/src/quantumhall_matrixelements/__init__.py
+++ b/src/quantumhall_matrixelements/__init__.py
@@ -10,15 +10,16 @@
 """
 from __future__ import annotations
 
+from importlib.metadata import PackageNotFoundError
+from importlib.metadata import version as _metadata_version
 from typing import TYPE_CHECKING
 
 import numpy as np
-from importlib.metadata import PackageNotFoundError, version as _metadata_version
 
-from .diagnostic import get_form_factors_opposite_field, get_exchange_kernels_opposite_field
-from .planewave import get_form_factors
+from .diagnostic import get_exchange_kernels_opposite_field, get_form_factors_opposite_field
 from .exchange_hankel import get_exchange_kernels_hankel
 from .exchange_legendre import get_exchange_kernels_GaussLegendre
+from .planewave import get_form_factors
 
 if TYPE_CHECKING:
     from numpy.typing import NDArray
@@ -28,13 +29,13 @@
 
 
 def get_exchange_kernels(
-    G_magnitudes: "RealArray",
-    G_angles: "RealArray",
+    G_magnitudes: RealArray,
+    G_angles: RealArray,
     nmax: int,
     *,
     method: str | None = None,
     **kwargs,
-) -> "ComplexArray":
+) -> ComplexArray:
     """Dispatcher for exchange kernels.
 
     Parameters
diff --git a/src/quantumhall_matrixelements/diagnostic.py b/src/quantumhall_matrixelements/diagnostic.py
index 1bd9ff3..917be85 100644
--- a/src/quantumhall_matrixelements/diagnostic.py
+++ b/src/quantumhall_matrixelements/diagnostic.py
@@ -18,7 +18,7 @@
 ]
 
 
-def get_form_factors_opposite_field(F: "ComplexArray") -> "ComplexArray":
+def get_form_factors_opposite_field(F: ComplexArray) -> ComplexArray:
     """Transform form factors to the opposite magnetic-field sign (σ→-σ).
 
     Parameters
@@ -39,7 +39,7 @@ def get_form_factors_opposite_field(F: "ComplexArray") -> "ComplexArray":
     return np.conj(F) * phase
 
 
-def get_exchange_kernels_opposite_field(Xs: "ComplexArray") -> "ComplexArray":
+def get_exchange_kernels_opposite_field(Xs: ComplexArray) -> ComplexArray:
     """Transform exchange kernels to the opposite magnetic-field sign (σ→-σ).
 
     Parameters
@@ -61,8 +61,8 @@ def get_exchange_kernels_opposite_field(Xs: "ComplexArray") -> "ComplexArray":
 
 
 def verify_exchange_kernel_symmetries(
-    G_magnitudes: "RealArray",
-    G_angles: "RealArray",
+    G_magnitudes: RealArray,
+    G_angles: RealArray,
     nmax: int,
     rtol: float = 1e-7,
     atol: float = 1e-9,
diff --git a/src/quantumhall_matrixelements/exchange_hankel.py b/src/quantumhall_matrixelements/exchange_hankel.py
index e63d52d..b69724b 100644
--- a/src/quantumhall_matrixelements/exchange_hankel.py
+++ b/src/quantumhall_matrixelements/exchange_hankel.py
@@ -1,7 +1,7 @@
 """Exchange kernels via Hankel transforms."""
 from __future__ import annotations
 
-from functools import lru_cache
+from functools import cache
 from typing import TYPE_CHECKING
 
 import numpy as np
@@ -23,7 +23,7 @@ def _N_order(n1: int, m1: int, n2: int, m2: int) -> int:
 def _parity_factor(N: int) -> int:
     return (-1) ** ((N - abs(N)) // 2)
 
-@lru_cache(maxsize=None)
+@cache
 def _get_hankel_transformer(order: int) -> HankelTransform:
     """Cached HankelTransform instance for a given Bessel order."""
     return HankelTransform(nu=order, N=6000, h=7e-6)
@@ -72,14 +72,14 @@ def _radial_exchange_integrand_rgamma(
 
 
 def get_exchange_kernels_hankel(
-    G_magnitudes: "RealArray",
-    G_angles: "RealArray",
+    G_magnitudes: RealArray,
+    G_angles: RealArray,
     nmax: int,
     *,
     potential: str | callable = "coulomb",
     kappa: float = 1.0,
     sign_magneticfield: int = -1,
-) -> "ComplexArray":
+) -> ComplexArray:
     """Compute X_{n1,m1,n2,m2}(G) via Hankel transforms (κ=1 convention).
 
     This backend parametrizes the radial integral via Hankel transforms with
diff --git a/src/quantumhall_matrixelements/exchange_legendre.py b/src/quantumhall_matrixelements/exchange_legendre.py
index f26d0e2..85e6bca 100644
--- a/src/quantumhall_matrixelements/exchange_legendre.py
+++ b/src/quantumhall_matrixelements/exchange_legendre.py
@@ -1,12 +1,11 @@
 """Exchange kernels via Gauss-Legendre quadrature with rational mapping."""
 from __future__ import annotations
 
-from functools import lru_cache
+from functools import cache
 from typing import TYPE_CHECKING
 
 import numpy as np
 import scipy.special as sps
-
 from scipy.special import roots_legendre
 
 if TYPE_CHECKING:
@@ -20,13 +19,13 @@
 
 def _parity_factor(N: int) -> int:
     """(-1)^((N-|N|)/2) → (-1)^N for N<0, and 1 for N>=0."""
-    return (-1) ** ((N - abs(N)) // 2) 
+    return (-1) ** ((N - abs(N)) // 2)
 
-@lru_cache(maxsize=None)
+@cache
 def _logfact(n: int) -> float:
     return float(sps.gammaln(n + 1))
 
-@lru_cache(maxsize=None)
+@cache
 def _legendre_nodes_weights_mapped(nquad: int, scale: float):
     """
     Gauss-Legendre nodes/weights mapped from [-1, 1] to [0, inf).
@@ -50,7 +49,7 @@ def get_exchange_kernels_GaussLegendre(
     scale: float = 0.5,
     ell: float = 1.0,
     sign_magneticfield: int = -1,
-) -> "ComplexArray":
+) -> ComplexArray:
     """Compute exchange kernels X_{n1,m1,n2,m2}(G) using Gauss-Legendre quadrature.
 
     This function evaluates the exchange matrix elements for a 2D electron gas
@@ -159,9 +158,7 @@ def get_exchange_kernels_GaussLegendre(
     arg = Gscaled[:, None] * sqrt2z[None, :]  # (nG, nquad)
 
     # Callable potential: evaluated once on the quadrature grid
-    if is_coulomb:
-        Veff = None
-    else:
+    if not is_coulomb:
         qvals = sqrt2z / float(ell)        # (nquad,)
         Veff = pot_fn(qvals) / (2.0 * np.pi * float(ell) ** 2)
         Veff = np.asarray(Veff)
diff --git a/src/quantumhall_matrixelements/planewave.py b/src/quantumhall_matrixelements/planewave.py
index 04a7b23..92845db 100644
--- a/src/quantumhall_matrixelements/planewave.py
+++ b/src/quantumhall_matrixelements/planewave.py
@@ -16,13 +16,13 @@
     IntArray = NDArray[np.int64]
 
 def _analytic_form_factor(
-    n_row: "IntArray",
-    n_col: "IntArray",
-    q_magnitudes: "RealArray",
-    q_angles: "RealArray",
+    n_row: IntArray,
+    n_col: IntArray,
+    q_magnitudes: RealArray,
+    q_angles: RealArray,
     lB: float,
     sign_magneticfield: int = -1,
-) -> "ComplexArray":
+) -> ComplexArray:
     """Vectorized Landau level form factor F_{n_row, n_col}(q).
 
     F_{n',n}(q) = i^{|n-n'|} e^{i(n-n')θ}
@@ -44,7 +44,7 @@ def _analytic_form_factor(
 
     laguerre_poly = eval_genlaguerre(n_min, delta_n_abs, arg_z)
 
-    angles = -sign_magneticfield * (n_col - n_row) * q_angles + (np.pi / 2) * delta_n_abs 
+    angles = -sign_magneticfield * (n_col - n_row) * q_angles + (np.pi / 2) * delta_n_abs
     angular_phase = np.cos(angles) + 1j * np.sin(angles)
 
     F = (
@@ -57,12 +57,12 @@ def _analytic_form_factor(
     return F
 
 def get_form_factors(
-    q_magnitudes: "RealArray",
-    q_angles: "RealArray",
+    q_magnitudes: RealArray,
+    q_angles: RealArray,
     nmax: int,
     lB: float = 1.0,
     sign_magneticfield: int = -1,
-) -> "ComplexArray":
+) -> ComplexArray:
     """Precompute F_{n',n}(G) for all G and Landau levels.
 
     Parameters
@@ -84,6 +84,8 @@ def get_form_factors(
     F : (nG, nmax, nmax) complex array
         Plane-wave form factors F_{n',n}(G).
     """
+    if sign_magneticfield not in (1, -1):
+        raise ValueError("sign_magneticfield must be 1 or -1")
     n_indices = np.arange(nmax)
     F = _analytic_form_factor(
         n_row=n_indices[None, :, None],
@@ -96,8 +98,8 @@ def get_form_factors(
     # Just to be explicit, we apply the symmetry transformation explicitly here
     # but we could have also passed sign_magneticfield to _analytic_form_factor
     # --> same result
-    if sign_magneticfield == 1: 
-        F = get_form_factors_opposite_field(F) 
+    if sign_magneticfield == 1:
+        F = get_form_factors_opposite_field(F)
 
     return F
 
diff --git a/tests/test_exchange_legendre.py b/tests/test_exchange_legendre.py
index f4d651a..12ef296 100644
--- a/tests/test_exchange_legendre.py
+++ b/tests/test_exchange_legendre.py
@@ -1,5 +1,7 @@
 import numpy as np
-from quantumhall_matrixelements import get_exchange_kernels_GaussLegendre, get_exchange_kernels
+
+from quantumhall_matrixelements import get_exchange_kernels, get_exchange_kernels_GaussLegendre
+
 
 def test_legendre_basic_shape():
     nmax = 2
diff --git a/tests/test_validation.py b/tests/test_validation.py
index 424460c..9bd57e6 100644
--- a/tests/test_validation.py
+++ b/tests/test_validation.py
@@ -1,7 +1,9 @@
 import numpy as np
+
 from quantumhall_matrixelements import get_exchange_kernels
 from quantumhall_matrixelements.diagnostic import verify_exchange_kernel_symmetries
 
+
 def test_cross_backend_consistency():
     """
     Verify that 'gausslegendre' and 'hankel' backends produce consistent results.
@@ -41,7 +43,7 @@ def test_large_n_consistency():
         Gs_dimless, thetas, nmax, method="hankel", sign_magneticfield=-1
     )
     
-    # At nmax=12, we expect ~1e-4 difference due to quadrature limits
+    # At nmax=12, differences up to ~3e-3 are acceptable due to quadrature limits
     assert np.allclose(X_gl, X_hk, rtol=3e-3, atol=3e-3), \
         "Mismatch at large nmax exceeded relaxed tolerance"