add stable high-spin precompute transforms (risbo recursion under hood)

Author: CosmoMatt

docs/api/precompute_transforms/alt_construct.rst

@@ -0,0 +1,7 @@
+:html_theme.sidebar_secondary.remove:
+
+**************************
+constructor (high-spin)
+**************************
+.. automodule:: s2fft.precompute_transforms.alt_construct
+   :members: 

docs/api/precompute_transforms/index.rst

@@ -60,6 +60,10 @@ Precompute Functions
      - Builds a kernel including quadrature weights and Wigner-D coefficients for spherical harmonic transform.
    * - :func:`~s2fft.precompute_transforms.construct.wigner_kernel`
      - Builds a kernel including quadrature weights and Wigner-D coefficients for Wigner transform.
+   * - :func:`~s2fft.precompute_transforms.alt_construct.spin_spherical_kernel`
+     - Builds a high-spin stable kernel including quadrature weights and Wigner-D coefficients for spherical harmonic transform.
+   * - :func:`~s2fft.precompute_transforms.alt_construct.wigner_kernel`
+     - Builds a high-spin stable kernel including quadrature weights and Wigner-D coefficients for Wigner transform.
    * - :func:`~s2fft.precompute_transforms.construct.healpix_phase_shifts`
      - Builds a vector of corresponding phase shifts for each HEALPix latitudinal ring.
 
@@ -69,6 +73,7 @@ Precompute Functions
    :caption: Precompute Transforms
 
    construct
+   alt_construct
    spin_spherical 
    wigner
 

s2fft/precompute_transforms/__init__.py

@@ -1,3 +1,4 @@
 from . import spherical
 from . import wigner
 from . import construct
+from . import alt_construct