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-rw-r--r--Doc/library/math.rst12
-rw-r--r--Lib/test/test_math.py103
-rw-r--r--Misc/NEWS.d/next/Library/2018-07-29-21-53-15.bpo-33089.hxbp3g.rst1
-rw-r--r--Modules/clinic/mathmodule.c.h37
-rw-r--r--Modules/mathmodule.c84
5 files changed, 236 insertions, 1 deletions
diff --git a/Doc/library/math.rst b/Doc/library/math.rst
index e60d029..76226c2 100644
--- a/Doc/library/math.rst
+++ b/Doc/library/math.rst
@@ -330,6 +330,18 @@ Trigonometric functions
Return the cosine of *x* radians.
+.. function:: dist(p, q)
+
+ Return the Euclidean distance between two points *p* and *q*, each
+ given as a tuple of coordinates. The two tuples must be the same size.
+
+ Roughly equivalent to::
+
+ sqrt(sum((px - qx) ** 2.0 for px, qx in zip(p, q)))
+
+ .. versionadded:: 3.8
+
+
.. function:: hypot(*coordinates)
Return the Euclidean norm, ``sqrt(sum(x**2 for x in coordinates))``.
diff --git a/Lib/test/test_math.py b/Lib/test/test_math.py
index 4843899..448110b 100644
--- a/Lib/test/test_math.py
+++ b/Lib/test/test_math.py
@@ -4,9 +4,11 @@
from test.support import run_unittest, verbose, requires_IEEE_754
from test import support
import unittest
+import itertools
import math
import os
import platform
+import random
import struct
import sys
import sysconfig
@@ -787,6 +789,107 @@ class MathTests(unittest.TestCase):
scale = FLOAT_MIN / 2.0 ** exp
self.assertEqual(math.hypot(4*scale, 3*scale), 5*scale)
+ def testDist(self):
+ from decimal import Decimal as D
+ from fractions import Fraction as F
+
+ dist = math.dist
+ sqrt = math.sqrt
+
+ # Simple exact case
+ self.assertEqual(dist((1, 2, 3), (4, 2, -1)), 5.0)
+
+ # Test different numbers of arguments (from zero to nine)
+ # against a straightforward pure python implementation
+ for i in range(9):
+ for j in range(5):
+ p = tuple(random.uniform(-5, 5) for k in range(i))
+ q = tuple(random.uniform(-5, 5) for k in range(i))
+ self.assertAlmostEqual(
+ dist(p, q),
+ sqrt(sum((px - qx) ** 2.0 for px, qx in zip(p, q)))
+ )
+
+ # Test allowable types (those with __float__)
+ self.assertEqual(dist((14.0, 1.0), (2.0, -4.0)), 13.0)
+ self.assertEqual(dist((14, 1), (2, -4)), 13)
+ self.assertEqual(dist((D(14), D(1)), (D(2), D(-4))), D(13))
+ self.assertEqual(dist((F(14, 32), F(1, 32)), (F(2, 32), F(-4, 32))),
+ F(13, 32))
+ self.assertEqual(dist((True, True, False, True, False),
+ (True, False, True, True, False)),
+ sqrt(2.0))
+
+ # Test corner cases
+ self.assertEqual(dist((13.25, 12.5, -3.25),
+ (13.25, 12.5, -3.25)),
+ 0.0) # Distance with self is zero
+ self.assertEqual(dist((), ()), 0.0) # Zero-dimensional case
+ self.assertEqual(1.0, # Convert negative zero to positive zero
+ math.copysign(1.0, dist((-0.0,), (0.0,)))
+ )
+ self.assertEqual(1.0, # Convert negative zero to positive zero
+ math.copysign(1.0, dist((0.0,), (-0.0,)))
+ )
+
+ # Verify tuple subclasses are allowed
+ class T(tuple): # tuple subclas
+ pass
+ self.assertEqual(dist(T((1, 2, 3)), ((4, 2, -1))), 5.0)
+
+ # Test handling of bad arguments
+ with self.assertRaises(TypeError): # Reject keyword args
+ dist(p=(1, 2, 3), q=(4, 5, 6))
+ with self.assertRaises(TypeError): # Too few args
+ dist((1, 2, 3))
+ with self.assertRaises(TypeError): # Too many args
+ dist((1, 2, 3), (4, 5, 6), (7, 8, 9))
+ with self.assertRaises(TypeError): # Scalars not allowed
+ dist(1, 2)
+ with self.assertRaises(TypeError): # Lists not allowed
+ dist([1, 2, 3], [4, 5, 6])
+ with self.assertRaises(TypeError): # Reject values without __float__
+ dist((1.1, 'string', 2.2), (1, 2, 3))
+ with self.assertRaises(ValueError): # Check dimension agree
+ dist((1, 2, 3, 4), (5, 6, 7))
+ with self.assertRaises(ValueError): # Check dimension agree
+ dist((1, 2, 3), (4, 5, 6, 7))
+
+
+ # Verify that the one dimensional case equivalent to abs()
+ for i in range(20):
+ p, q = random.random(), random.random()
+ self.assertEqual(dist((p,), (q,)), abs(p - q))
+
+ # Test special values
+ values = [NINF, -10.5, -0.0, 0.0, 10.5, INF, NAN]
+ for p in itertools.product(values, repeat=3):
+ for q in itertools.product(values, repeat=3):
+ diffs = [px - qx for px, qx in zip(p, q)]
+ if any(map(math.isinf, diffs)):
+ # Any infinite difference gives positive infinity.
+ self.assertEqual(dist(p, q), INF)
+ elif any(map(math.isnan, diffs)):
+ # If no infinity, any NaN gives a Nan.
+ self.assertTrue(math.isnan(dist(p, q)))
+
+ # Verify scaling for extremely large values
+ fourthmax = FLOAT_MAX / 4.0
+ for n in range(32):
+ p = (fourthmax,) * n
+ q = (0.0,) * n
+ self.assertEqual(dist(p, q), fourthmax * math.sqrt(n))
+ self.assertEqual(dist(q, p), fourthmax * math.sqrt(n))
+
+ # Verify scaling for extremely small values
+ for exp in range(32):
+ scale = FLOAT_MIN / 2.0 ** exp
+ p = (4*scale, 3*scale)
+ q = (0.0, 0.0)
+ self.assertEqual(math.dist(p, q), 5*scale)
+ self.assertEqual(math.dist(q, p), 5*scale)
+
+
def testLdexp(self):
self.assertRaises(TypeError, math.ldexp)
self.ftest('ldexp(0,1)', math.ldexp(0,1), 0)
diff --git a/Misc/NEWS.d/next/Library/2018-07-29-21-53-15.bpo-33089.hxbp3g.rst b/Misc/NEWS.d/next/Library/2018-07-29-21-53-15.bpo-33089.hxbp3g.rst
new file mode 100644
index 0000000..9b253d0
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2018-07-29-21-53-15.bpo-33089.hxbp3g.rst
@@ -0,0 +1 @@
+Add math.dist() to compute the Euclidean distance between two points.
diff --git a/Modules/clinic/mathmodule.c.h b/Modules/clinic/mathmodule.c.h
index 3a487bd..c4d2786 100644
--- a/Modules/clinic/mathmodule.c.h
+++ b/Modules/clinic/mathmodule.c.h
@@ -269,6 +269,41 @@ exit:
return return_value;
}
+PyDoc_STRVAR(math_dist__doc__,
+"dist($module, p, q, /)\n"
+"--\n"
+"\n"
+"Return the Euclidean distance between two points p and q.\n"
+"\n"
+"The points should be specified as tuples of coordinates.\n"
+"Both tuples must be the same size.\n"
+"\n"
+"Roughly equivalent to:\n"
+" sqrt(sum((px - qx) ** 2.0 for px, qx in zip(p, q)))");
+
+#define MATH_DIST_METHODDEF \
+ {"dist", (PyCFunction)math_dist, METH_FASTCALL, math_dist__doc__},
+
+static PyObject *
+math_dist_impl(PyObject *module, PyObject *p, PyObject *q);
+
+static PyObject *
+math_dist(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
+{
+ PyObject *return_value = NULL;
+ PyObject *p;
+ PyObject *q;
+
+ if (!_PyArg_ParseStack(args, nargs, "O!O!:dist",
+ &PyTuple_Type, &p, &PyTuple_Type, &q)) {
+ goto exit;
+ }
+ return_value = math_dist_impl(module, p, q);
+
+exit:
+ return return_value;
+}
+
PyDoc_STRVAR(math_pow__doc__,
"pow($module, x, y, /)\n"
"--\n"
@@ -487,4 +522,4 @@ math_isclose(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject
exit:
return return_value;
}
-/*[clinic end generated code: output=1c35516a10443902 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=d936137c1189b89b input=a9049054013a1b77]*/
diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
index 726fc56..8f11f2c 100644
--- a/Modules/mathmodule.c
+++ b/Modules/mathmodule.c
@@ -2031,6 +2031,89 @@ math_fmod_impl(PyObject *module, double x, double y)
return PyFloat_FromDouble(r);
}
+/*[clinic input]
+math.dist
+
+ p: object(subclass_of='&PyTuple_Type')
+ q: object(subclass_of='&PyTuple_Type')
+ /
+
+Return the Euclidean distance between two points p and q.
+
+The points should be specified as tuples of coordinates.
+Both tuples must be the same size.
+
+Roughly equivalent to:
+ sqrt(sum((px - qx) ** 2.0 for px, qx in zip(p, q)))
+[clinic start generated code]*/
+
+static PyObject *
+math_dist_impl(PyObject *module, PyObject *p, PyObject *q)
+/*[clinic end generated code: output=56bd9538d06bbcfe input=937122eaa5f19272]*/
+{
+ PyObject *item;
+ double *diffs;
+ double max = 0.0;
+ double csum = 0.0;
+ double x, px, qx, result;
+ Py_ssize_t i, m, n;
+ int found_nan = 0;
+
+ m = PyTuple_GET_SIZE(p);
+ n = PyTuple_GET_SIZE(q);
+ if (m != n) {
+ PyErr_SetString(PyExc_ValueError,
+ "both points must have the same number of dimensions");
+ return NULL;
+
+ }
+ diffs = (double *) PyObject_Malloc(n * sizeof(double));
+ if (diffs == NULL) {
+ return NULL;
+ }
+ for (i=0 ; i<n ; i++) {
+ item = PyTuple_GET_ITEM(p, i);
+ px = PyFloat_AsDouble(item);
+ if (px == -1.0 && PyErr_Occurred()) {
+ PyObject_Free(diffs);
+ return NULL;
+ }
+ item = PyTuple_GET_ITEM(q, i);
+ qx = PyFloat_AsDouble(item);
+ if (qx == -1.0 && PyErr_Occurred()) {
+ PyObject_Free(diffs);
+ return NULL;
+ }
+ x = fabs(px - qx);
+ diffs[i] = x;
+ found_nan |= Py_IS_NAN(x);
+ if (x > max) {
+ max = x;
+ }
+ }
+ if (Py_IS_INFINITY(max)) {
+ result = max;
+ goto done;
+ }
+ if (found_nan) {
+ result = Py_NAN;
+ goto done;
+ }
+ if (max == 0.0) {
+ result = 0.0;
+ goto done;
+ }
+ for (i=0 ; i<n ; i++) {
+ x = diffs[i] / max;
+ csum += x * x;
+ }
+ result = max * sqrt(csum);
+
+ done:
+ PyObject_Free(diffs);
+ return PyFloat_FromDouble(result);
+}
+
/* AC: cannot convert yet, waiting for *args support */
static PyObject *
math_hypot(PyObject *self, PyObject *args)
@@ -2358,6 +2441,7 @@ static PyMethodDef math_methods[] = {
{"cos", math_cos, METH_O, math_cos_doc},
{"cosh", math_cosh, METH_O, math_cosh_doc},
MATH_DEGREES_METHODDEF
+ MATH_DIST_METHODDEF
{"erf", math_erf, METH_O, math_erf_doc},
{"erfc", math_erfc, METH_O, math_erfc_doc},
{"exp", math_exp, METH_O, math_exp_doc},
generated by cgit v0.12 at 2024-11-17 05:09:12 (GMT)