DOC: Release notes for frozen dimensions.

1 files changed, 15 insertions, 0 deletions

diff --git a/doc/release/1.16.0-notes.rst b/doc/release/1.16.0-notes.rst
index ae21f4ffd..1fd4a17e6 100644
--- a/doc/release/1.16.0-notes.rst
+++ b/doc/release/1.16.0-notes.rst
@@ -62,6 +62,21 @@ behavior will be appending.  This applied to: `LDFLAGS`, `F77FLAGS`,
 `F90FLAGS`, `FREEFLAGS`, `FOPT`, `FDEBUG`, and `FFLAGS`.  See gh-11525 for more
 details.
 
+Generalized ufunc signatures now allow fixed-size dimensions
+------------------------------------------------------------
+By using a numerical value in the signature of a generalized ufunc, one can
+indicate that the given function requires input or output to have dimensions
+with the given size. E.g., the signature of a function that converts a polar
+angle to a two-dimensional cartesian unit vector would be ``()->(2)``; that
+for one that converts two spherical angles to a three-dimensional unit vector
+would be ``(),()->(3)``; and that for the cross product of two
+three-dimensional vectors would be ``(3),(3)->(3)``.
+
+Note that to the elementary function these dimensions are not treated any
+differently from variable ones indicated with a name starting with a letter;
+the loop still is passed the corresponding size, but it can now count on that
+size being equal to the fixed one given in the signature.
+
 Changes
 =======