address review

Author: picnixz

Doc/library/math.rst

@@ -253,8 +253,8 @@ Floating point arithmetic
 
    Get the larger of two floating-point values, treating NaNs as missing data.
 
-   If *x* and *y* are NaNs of same sign *s*, return ``copysign(nan, s)``.
-   If *x* and *y* are NaNs of different sign, return ``copysign(nan, 1)``.
+   When both operands are NaNs, return ``nan`` (the sign of the result is
+   implementation-defined).
 
    .. versionadded:: next
 
@@ -263,8 +263,8 @@ Floating point arithmetic
 
    Get the smaller of two floating-point values, treating NaNs as missing data.
 
-   If *x* and *y* are NaNs of same sign *s*, return ``copysign(nan, s)``.
-   If *x* and *y* are NaNs of different sign, return ``copysign(nan, -1)``.
+   When both operands are NaNs, return ``nan`` (the sign of the result is
+   implementation-defined).
 
    .. versionadded:: next
 

Lib/test/test_math.py

@@ -38,11 +38,6 @@
 test_file = os.path.join(test_dir, 'mathdata', 'cmath_testcases.txt')
 
 
-def is_signed_nan(x, x0):
-    """Check if x is a NaN with the same sign as x0."""
-    return math.isnan(x) and math.copysign(1, x) == math.copysign(1, x0)
-
-
 def to_ulps(x):
     """Convert a non-NaN float x to an integer, in such a way that
     adjacent floats are converted to adjacent integers.  Then
@@ -670,12 +665,11 @@ def test_fmax_nans(self):
                 self.assertFalse(math.isnan(math.fmax(x, NAN)))
                 self.assertFalse(math.isnan(math.fmax(NNAN, x)))
                 self.assertFalse(math.isnan(math.fmax(x, NNAN)))
-        # When operands are NaNs with identical sign, return this signed NaN.
-        self.assertTrue(is_signed_nan(math.fmax(NAN, NAN), 1))
-        self.assertTrue(is_signed_nan(math.fmax(NNAN, NNAN), -1))
-        # When operands are NaNs of different signs, return the positive NaN.
-        self.assertTrue(is_signed_nan(math.fmax(NAN, NNAN), 1))
-        self.assertTrue(is_signed_nan(math.fmax(NNAN, NAN), 1))
+        # When both operands are NaNs, fmax() returns NaN (see C11, F.10.9.2).
+        self.assertTrue(math.isnan(math.fmax(NAN, NAN)))
+        self.assertTrue(math.isnan(math.fmax(NNAN, NNAN)))
+        self.assertTrue(math.isnan(math.fmax(NAN, NNAN)))
+        self.assertTrue(math.isnan(math.fmax(NNAN, NAN)))
 
     def test_fmin(self):
         self.assertRaises(TypeError, math.fmin)
@@ -718,12 +712,11 @@ def test_fmin_nans(self):
                 self.assertFalse(math.isnan(math.fmin(x, NAN)))
                 self.assertFalse(math.isnan(math.fmin(NNAN, x)))
                 self.assertFalse(math.isnan(math.fmin(x, NNAN)))
-        # When operands are NaNs with identical sign, return this signed NaN.
-        self.assertTrue(is_signed_nan(math.fmin(NAN, NAN), 1))
-        self.assertTrue(is_signed_nan(math.fmin(NNAN, NNAN), -1))
-        # When operands are NaNs of different signs, return the negative NaN.
-        self.assertTrue(is_signed_nan(math.fmin(NAN, NNAN), -1))
-        self.assertTrue(is_signed_nan(math.fmin(NNAN, NAN), -1))
+        # When both operands are NaNs, fmax() returns NaN (see C11, F.10.9.2).
+        self.assertTrue(math.isnan(math.fmin(NAN, NAN)))
+        self.assertTrue(math.isnan(math.fmin(NNAN, NNAN)))
+        self.assertTrue(math.isnan(math.fmin(NAN, NNAN)))
+        self.assertTrue(math.isnan(math.fmin(NNAN, NAN)))
 
     def testFrexp(self):
         self.assertRaises(TypeError, math.frexp)

Modules/mathmodule.c

@@ -1222,17 +1222,12 @@ math.fmax -> double
     /
 
 Returns the larger of two floating-point arguments.
-
 [clinic start generated code]*/
 
 static double
 math_fmax_impl(PyObject *module, double x, double y)
-/*[clinic end generated code: output=00692358d312fee2 input=0dcf618bb27f98c7]*/
+/*[clinic end generated code: output=00692358d312fee2 input=e64ab9f40a60f4f1]*/
 {
-    if (isnan(x) && isnan(y)) {
-        double s = copysign(1, x);
-        return s == copysign(1, y) ? copysign(NAN, s) : NAN;
-    }
     return fmax(x, y);
 }
 
@@ -1250,11 +1245,6 @@ static double
 math_fmin_impl(PyObject *module, double x, double y)
 /*[clinic end generated code: output=3d5b7826bd292dd9 input=f7b5c91de01d766f]*/
 {
-    if (isnan(x) && isnan(y)) {
-        double s = copysign(1, x);
-        // return ±NAN if both are ±NAN and -NAN otherwise.
-        return copysign(NAN, s == copysign(1, y) ? s : -1);
-    }
     return fmin(x, y);
 }