touch up Unalmis PR [no ci]

Author: ahbarnett

CHANGELOG

@@ -3,7 +3,7 @@ If not stated, FINUFFT is assumed (cuFINUFFT <=1.3 is listed separately).
 
 Master (working towards v2.5.0), 8/13/25
 
-* Added real-valued function type-2 interpolation demo (Barnett).
+* Added real-valued function type-2 interpolation demos (Barnett, Unalmis #722)
 * Added functionality for adjoint execution of FINUFFT plans (Reinecke #633,
   addresses #566 and #571).
   Work arrays are now only allocated during plan execution, reducing overall

docs/tutorial/realinterp1d.rst

@@ -1,7 +1,11 @@
 .. _realinterp1d:
 
-Fast Fourier interpolation of 1D real-valued function at arbitrary points
-=========================================================================
+Fast Fourier interpolation of a real-valued function at arbitrary points
+========================================================================
+
+1D
+~~
+
 
 This is a Python variant of the previous 1D MATLAB demo, but illustrating
 a trick for **real-valued** functions.
@@ -63,13 +67,21 @@ When run this gives:
 
 which shows that both schemes work.
 See the full code `tutorial/realinterp1d.py <https://github.com/flatironinstitute/finufft/blob/master/tutorial/realinterp1d.py>`_.
-See the full code `tutorial/realinterp2d.py <https://github.com/flatironinstitute/finufft/blob/master/tutorial/realinterp2d.py>`_.
 This arose from Discussion https://github.com/flatironinstitute/finufft/discussions/720
 
-
 .. note::
 
     Complex-valued spreading/interpolation is still used under the hood in FINUFFT, so that there is no
     efficiency gain on the nonuniform point side,
     possibly motivating real-valued NUFFT variants. Since the decisions about
     real-valued interfaces become elaborate, we leave this for future work.
+
+2D
+~~
+
+A demo (including a ``pytest`` framework) for the 2D version of the above
+1D code has been written by Kaya Unalmis, arising from the above discussion.
+The idea in 2D is to use the above trick for one of the dimensions, then
+perform the usual complex evaluation in the other dimension;
+this is somewhat neater than using Hermitian inversion symmetry in 2D.
+The code is at `tutorial/realinterp2d.py <https://github.com/flatironinstitute/finufft/blob/master/tutorial/realinterp2d.py>`_.

tutorial/realinterp2d.py

@@ -1,4 +1,6 @@
 # Written by Kaya Unalmis following discussion with Barnett on 08/15/25.
+# [Note added by Barnett: some of the notation used here differs from
+# the standard notation of FINUFFT docs. However it is a nice demo.]
 
 import numpy as np
 import finufft as fi