pythongh-135853: add math.fmax and math.fmin (python#135888)

Author: picnixz

Doc/library/math.rst

@@ -42,6 +42,8 @@ noted otherwise, all return values are floats.
 :func:`fabs(x) <fabs>`                                Absolute value of *x*
 :func:`floor(x)  <floor>`                             Floor of *x*, the largest integer less than or equal to *x*
 :func:`fma(x, y, z) <fma>`                            Fused multiply-add operation: ``(x * y) + z``
+:func:`fmax(x, y) <fmax>`                             Maximum of two floating-point values
+:func:`fmin(x, y) <fmin>`                             Minimum of two floating-point values
 :func:`fmod(x, y) <fmod>`                             Remainder of division ``x / y``
 :func:`modf(x) <modf>`                                Fractional and integer parts of *x*
 :func:`remainder(x, y) <remainder>`                   Remainder of *x* with respect to *y*
@@ -248,6 +250,30 @@ Floating point arithmetic
    .. versionadded:: 3.13
 
 
+.. function:: fmax(x, y)
+
+   Get the larger of two floating-point values, treating NaNs as missing data.
+
+   When both operands are (signed) NaNs or zeroes, return ``nan`` and ``0``
+   respectively and the sign of the result is implementation-defined, that
+   is, :func:`!fmax` is not required to be sensitive to the sign of such
+   operands (see Annex F of the C11 standard, §F.10.0.3 and §F.10.9.2).
+
+   .. versionadded:: next
+
+
+.. function:: fmin(x, y)
+
+   Get the smaller of two floating-point values, treating NaNs as missing data.
+
+   When both operands are (signed) NaNs or zeroes, return ``nan`` and ``0``
+   respectively and the sign of the result is implementation-defined, that
+   is, :func:`!fmin` is not required to be sensitive to the sign of such
+   operands (see Annex F of the C11 standard, §F.10.0.3 and §F.10.9.3).
+
+   .. versionadded:: next
+
+
 .. function:: fmod(x, y)
 
    Return the floating-point remainder of ``x / y``,

Doc/whatsnew/3.15.rst

@@ -212,7 +212,7 @@ math
 * Add :func:`math.isnormal` and :func:`math.issubnormal` functions.
   (Contributed by Sergey B Kirpichev in :gh:`132908`.)
 
-* Add :func:`math.signbit` function.
+* Add :func:`math.fmax`, :func:`math.fmin` and :func:`math.signbit` functions.
   (Contributed by Bénédikt Tran in :gh:`135853`.)
 
 

Lib/test/test_math.py

@@ -17,6 +17,7 @@
 
 eps = 1E-05
 NAN = float('nan')
+NNAN = float('-nan')
 INF = float('inf')
 NINF = float('-inf')
 FLOAT_MAX = sys.float_info.max
@@ -636,6 +637,92 @@ def testFmod(self):
         self.assertEqual(math.fmod(0.0, NINF), 0.0)
         self.assertRaises(ValueError, math.fmod, INF, INF)
 
+    def test_fmax(self):
+        self.assertRaises(TypeError, math.fmax)
+        self.assertRaises(TypeError, math.fmax, 'x', 'y')
+
+        self.assertEqual(math.fmax(0., 0.), 0.)
+        self.assertEqual(math.fmax(1., 2.), 2.)
+        self.assertEqual(math.fmax(2., 1.), 2.)
+
+        self.assertEqual(math.fmax(+1., +0.), 1.)
+        self.assertEqual(math.fmax(+0., +1.), 1.)
+        self.assertEqual(math.fmax(+1., -0.), 1.)
+        self.assertEqual(math.fmax(-0., +1.), 1.)
+
+        self.assertEqual(math.fmax(-1., +0.), 0.)
+        self.assertEqual(math.fmax(+0., -1.), 0.)
+        self.assertEqual(math.fmax(-1., -0.), 0.)
+        self.assertEqual(math.fmax(-0., -1.), 0.)
+
+        for x in [NINF, -1., -0., 0., 1., INF]:
+            self.assertFalse(math.isnan(x))
+
+            with self.subTest(x=x, is_negative=math.copysign(1, x) < 0):
+                self.assertEqual(math.fmax(INF, x), INF)
+                self.assertEqual(math.fmax(x, INF), INF)
+                self.assertEqual(math.fmax(NINF, x), x)
+                self.assertEqual(math.fmax(x, NINF), x)
+
+    @requires_IEEE_754
+    def test_fmax_nans(self):
+        # When exactly one operand is NaN, the other is returned.
+        for x in [NINF, -1., -0., 0., 1., INF]:
+            with self.subTest(x=x, is_negative=math.copysign(1, x) < 0):
+                self.assertFalse(math.isnan(math.fmax(NAN, x)))
+                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 both operands are NaNs, fmax() returns NaN (see C11, F.10.9.2)
+        # whose sign is implementation-defined (see C11, F.10.0.3).
+        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)
+        self.assertRaises(TypeError, math.fmin, 'x', 'y')
+
+        self.assertEqual(math.fmin(0., 0.), 0.)
+        self.assertEqual(math.fmin(1., 2.), 1.)
+        self.assertEqual(math.fmin(2., 1.), 1.)
+
+        self.assertEqual(math.fmin(+1., +0.), 0.)
+        self.assertEqual(math.fmin(+0., +1.), 0.)
+        self.assertEqual(math.fmin(+1., -0.), 0.)
+        self.assertEqual(math.fmin(-0., +1.), 0.)
+
+        self.assertEqual(math.fmin(-1., +0.), -1.)
+        self.assertEqual(math.fmin(+0., -1.), -1.)
+        self.assertEqual(math.fmin(-1., -0.), -1.)
+        self.assertEqual(math.fmin(-0., -1.), -1.)
+
+        for x in [NINF, -1., -0., 0., 1., INF]:
+            self.assertFalse(math.isnan(x))
+
+            with self.subTest(x=x, is_negative=math.copysign(1, x) < 0):
+                self.assertEqual(math.fmin(INF, x), x)
+                self.assertEqual(math.fmin(x, INF), x)
+                self.assertEqual(math.fmin(NINF, x), NINF)
+                self.assertEqual(math.fmin(x, NINF), NINF)
+
+    @requires_IEEE_754
+    def test_fmin_nans(self):
+        # When exactly one operand is NaN, the other is returned.
+        for x in [NINF, -1., -0., 0., 1., INF]:
+            with self.subTest(x=x, is_negative=math.copysign(1, x) < 0):
+                self.assertFalse(math.isnan(math.fmin(NAN, x)))
+                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 both operands are NaNs, fmin() returns NaN (see C11, F.10.9.3)
+        # whose sign is implementation-defined (see C11, F.10.0.3).
+        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)
 

Misc/NEWS.d/next/Library/2025-06-24-13-30-47.gh-issue-135853.7ejTvK.rst

@@ -0,0 +1,2 @@
+Add :func:`math.fmax` and :func:`math.fmin` to get the larger and smaller of
+two floating-point values. Patch by Bénédikt Tran.

Modules/clinic/mathmodule.c.h

@@ -1214,6 +1214,40 @@ math_floor(PyObject *module, PyObject *number)
     return PyLong_FromDouble(floor(x));
 }
 
+/*[clinic input]
+math.fmax -> double
+
+    x: double
+    y: double
+    /
+
+Return 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=021596c027336ffe]*/
+{
+    return fmax(x, y);
+}
+
+/*[clinic input]
+math.fmin -> double
+
+    x: double
+    y: double
+    /
+
+Return the smaller of two floating-point arguments.
+[clinic start generated code]*/
+
+static double
+math_fmin_impl(PyObject *module, double x, double y)
+/*[clinic end generated code: output=3d5b7826bd292dd9 input=d12e64ccc33f878a]*/
+{
+    return fmin(x, y);
+}
+
 FUNC1AD(gamma, m_tgamma,
       "gamma($module, x, /)\n--\n\n"
       "Gamma function at x.",
@@ -4192,7 +4226,9 @@ static PyMethodDef math_methods[] = {
     MATH_FACTORIAL_METHODDEF
     MATH_FLOOR_METHODDEF
     MATH_FMA_METHODDEF
+    MATH_FMAX_METHODDEF
     MATH_FMOD_METHODDEF
+    MATH_FMIN_METHODDEF
     MATH_FREXP_METHODDEF
     MATH_FSUM_METHODDEF
     {"gamma",           math_gamma,     METH_O,         math_gamma_doc},