Add draft implementation for nextafter

Author: asmeurer

array_api_strict/__init__.py

@@ -172,6 +172,7 @@
     minimum,
     multiply,
     negative,
+    nextafter,
     not_equal,
     positive,
     pow,
@@ -240,6 +241,7 @@
     "minimum",
     "multiply",
     "negative",
+    "nextafter",
     "not_equal",
     "positive",
     "pow",

array_api_strict/_elementwise_functions.py

@@ -805,6 +805,20 @@ def negative(x: Array, /) -> Array:
     return Array._new(np.negative(x._array), device=x.device)
 
 
+@requires_api_version('2024.12')
+def nextafter(x1: Array, x2: Array, /) -> Array:
+    """
+    Array API compatible wrapper for :py:func:`np.nextafter <numpy.nextafter>`.
+
+    See its docstring for more information.
+    """
+    if x1.device != x2.device:
+        raise ValueError(f"Arrays from two different devices ({x1.device} and {x2.device}) can not be combined.")
+    if x1.dtype not in _real_floating_dtypes or x2.dtype not in _real_floating_dtypes:
+        raise TypeError("Only real floating-point dtypes are allowed in nextafter")
+    x1, x2 = Array._normalize_two_args(x1, x2)
+    return Array._new(np.nextafter(x1._array, x2._array), device=x1.device)
+
 def not_equal(x1: Array, x2: Array, /) -> Array:
     """
     Array API compatible wrapper for :py:func:`np.not_equal <numpy.not_equal>`.

array_api_strict/tests/test_elementwise_functions.py

@@ -2,6 +2,8 @@
 
 from numpy.testing import assert_raises
 
+import pytest
+
 from .. import asarray, _elementwise_functions
 from .._elementwise_functions import bitwise_left_shift, bitwise_right_shift
 from .._dtypes import (
@@ -79,6 +81,7 @@ def nargs(func):
     "minimum": "real numeric",
     "multiply": "numeric",
     "negative": "numeric",
+    "nextafter": "real floating-point",
     "not_equal": "all",
     "positive": "numeric",
     "pow": "numeric",
@@ -126,7 +129,8 @@ def _array_vals(dtypes):
             yield asarray(1., dtype=d)
 
     # Use the latest version of the standard so all functions are included
-    set_array_api_strict_flags(api_version="2023.12")
+    with pytest.warns(UserWarning):
+        set_array_api_strict_flags(api_version="2024.12")
 
     for func_name, types in elementwise_function_input_types.items():
         dtypes = _dtype_categories[types]
@@ -162,7 +166,8 @@ def _array_vals():
             yield asarray(1.0, dtype=d)
 
     # Use the latest version of the standard so all functions are included
-    set_array_api_strict_flags(api_version="2023.12")
+    with pytest.warns(UserWarning):
+        set_array_api_strict_flags(api_version="2024.12")
 
     for x in _array_vals():
         for func_name, types in elementwise_function_input_types.items():

array_api_strict/tests/test_flags.py

@@ -284,6 +284,7 @@ def test_fft(func_name):
 
 api_version_2024_12_examples = {
     'diff': lambda: xp.diff(xp.asarray([0, 1, 2])),
+    'nextafter': lambda: xp.nextafter(xp.asarray(0.), xp.asarray(1.)),
 }
 
 @pytest.mark.parametrize('func_name', api_version_2023_12_examples.keys())