Clarify expected results for any and all when operating on empty arrays (#388)

* Clarify expected results for `any` and `all` when operating on empty arrays

* Update copy

Author: kgryte

spec/API_specification/signatures/utility_functions.py

@@ -4,6 +4,12 @@ def all(x: array, /, *, axis: Optional[Union[int, Tuple[int, ...]]] = None, keep
     """
     Tests whether all input array elements evaluate to ``True`` along a specified axis.
 
+    .. note::
+       Positive infinity, negative infinity, and NaN must evaluate to ``True``.
+
+    .. note::
+       If ``x`` is an empty array or the size of the axis (dimension) along which to evaluate elements is zero, the test result must be ``True``.
+
     Parameters
     ----------
     x: array
@@ -23,6 +29,12 @@ def any(x: array, /, *, axis: Optional[Union[int, Tuple[int, ...]]] = None, keep
     """
     Tests whether any input array element evaluates to ``True`` along a specified axis.
 
+    .. note::
+       Positive infinity, negative infinity, and NaN must evaluate to ``True``.
+
+    .. note::
+       If ``x`` is an empty array or the size of the axis (dimension) along which to evaluate elements is zero, the test result must be ``False``.
+
     Parameters
     ----------
     x: array