BUG: Return scalars from ufunclike objects

No need to reinvent the wheel here - the ufunc machinery will handle the out arguments Fixes #8993
numpy · mhvk · Apr 28, 2017 · Apr 26, 2017 · Apr 26, 2017 · Apr 26, 2017
commit 05f422827b3317ad3774cbd1859edbf6bc196f75
diff --git a/numpy/lib/tests/test_ufunclike.py b/numpy/lib/tests/test_ufunclike.py
@@ -1,5 +1,6 @@
 from __future__ import division, absolute_import, print_function
 
+import numpy as np
 import numpy.core as nx
 import numpy.lib.ufunclike as ufl
 from numpy.testing import (
@@ -62,11 +63,35 @@ def __array_wrap__(self, obj, context=None):
         assert_(isinstance(f, MyArray))
         assert_equal(f.metadata, 'foo')
 
+        # check 0d arrays don't decay to scalars
+        m0d = m[0,...]
+        m0d.metadata = 'bar'
+        f0d = ufl.fix(m0d)
+        assert_(isinstance(f0d, MyArray))
+        assert_equal(f0d.metadata, 'bar')
+
     def test_deprecated(self):
         # NumPy 1.13.0, 2017-04-26
         assert_warns(DeprecationWarning, ufl.fix, [1, 2], y=nx.empty(2))
         assert_warns(DeprecationWarning, ufl.isposinf, [1, 2], y=nx.empty(2))
         assert_warns(DeprecationWarning, ufl.isneginf, [1, 2], y=nx.empty(2))
 
+    def test_scalar(self):
+        x = np.inf
+        actual = np.isposinf(x)
+        expected = np.True_
+        assert_equal(actual, expected)
+        assert_equal(type(actual), type(expected))
+
+        x = -3.4
+        actual = np.fix(x)
+        expected = np.float64(-3.0)
+        assert_equal(actual, expected)
+        assert_equal(type(actual), type(expected))
+
+        out = np.array(0.0)
+        actual = np.fix(x, out=out)
+        assert_(actual is out)
+
 if __name__ == "__main__":
     run_module_suite()
diff --git a/numpy/lib/ufunclike.py b/numpy/lib/ufunclike.py
@@ -71,14 +71,15 @@ def fix(x, out=None):
     array([ 2.,  2., -2., -2.])
 
     """
-    x = nx.asanyarray(x)
-    y1 = nx.floor(x)
-    y2 = nx.ceil(x)
-    if out is None:
-        out = nx.asanyarray(y1)
-    out[...] = nx.where(x >= 0, y1, y2)
-    return out
+    # promote back to an array if flattened
+    res = nx.asanyarray(nx.ceil(x, out=out))
+    res = nx.floor(x, out=res, where=nx.greater_equal(x, 0))
 
+    # when no out argument is passed and no subclasses are involved, flatten
+    # scalars
+    if out is None and type(res) is nx.ndarray:
+        res = res[()]
+    return res
 
 @_deprecate_out_named_y
 def isposinf(x, out=None):
@@ -137,11 +138,7 @@ def isposinf(x, out=None):
     array([0, 0, 1])
 
     """
-    if y is None:
-        x = nx.asarray(x)
-        out = nx.empty(x.shape, dtype=nx.bool_)
-    nx.logical_and(nx.isinf(x), ~nx.signbit(x), out)
-    return out
+    return nx.logical_and(nx.isinf(x), ~nx.signbit(x), out)
 
 
 @_deprecate_out_named_y
@@ -202,8 +199,4 @@ def isneginf(x, out=None):
     array([1, 0, 0])
 
     """
-    if out is None:
-        x = nx.asarray(x)
-        out = nx.empty(x.shape, dtype=nx.bool_)
-    nx.logical_and(nx.isinf(x), nx.signbit(x), out)
-    return out
+    return nx.logical_and(nx.isinf(x), nx.signbit(x), out)