bpo-39479:Add math.lcm() function: Least Common Multiple (#18547)

* Update math.rst

* Update math.rst

* updated whats new

* Update test_math.py

* Update mathmodule.c

* Update mathmodule.c.h

* Update ACKS

* 📜🤖 Added by blurb_it.

* Update 3.9.rst

* Update 2020-02-18-12-37-16.bpo-39479.j3UcCq.rst

* Update math.rst

* Update 2020-02-18-12-37-16.bpo-39479.j3UcCq.rst

* Update test_math.py

* Update ACKS

* Update mathmodule.c.h

* Update mathmodule.c

* Update mathmodule.c.h

* Update mathmodule.c.h

Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>

2 files changed, 85 insertions, 1 deletions

diff --git a/Modules/clinic/mathmodule.c.h b/Modules/clinic/mathmodule.c.h
index f95d291d41..df45a1a0c5 100644
--- a/Modules/clinic/mathmodule.c.h
+++ b/Modules/clinic/mathmodule.c.h
@@ -85,6 +85,36 @@ PyDoc_STRVAR(math_factorial__doc__,
 #define MATH_FACTORIAL_METHODDEF    \
     {"factorial", (PyCFunction)math_factorial, METH_O, math_factorial__doc__},
 
+PyDoc_STRVAR(math_lcm__doc__,
+"lcm($module, x, y, /)\n"
+"--\n"
+"\n"
+"least common multiple of x and y");
+
+#define MATH_LCM_METHODDEF    \
+    {"lcm", (PyCFunction)(void(*)(void))math_lcm, METH_FASTCALL, math_lcm__doc__},
+
+static PyObject *
+math_lcm_impl(PyObject *module, PyObject *a, PyObject *b);
+
+static PyObject *
+math_lcm(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
+{
+    PyObject *return_value = NULL;
+    PyObject *a;
+    PyObject *b;
+
+    if (!_PyArg_CheckPositional("lcm", nargs, 2, 2)) {
+        goto exit;
+    }
+    a = args[0];
+    b = args[1];
+    return_value = math_lcm_impl(module, a, b);
+
+exit:
+    return return_value;
+}
+
 PyDoc_STRVAR(math_trunc__doc__,
 "trunc($module, x, /)\n"
 "--\n"
@@ -895,4 +925,4 @@ math_ulp(PyObject *module, PyObject *arg)
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=9b51d215dbcac060 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=f8daa185c043a7b7 input=a9049054013a1b77]*/
diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
index 309f229159..f74b7e1a34 100644
--- a/Modules/mathmodule.c
+++ b/Modules/mathmodule.c
@@ -2018,6 +2018,59 @@ math_factorial(PyObject *module, PyObject *arg)
 
 
 /*[clinic input]
+math.lcm
+    x as a: object
+    y as b: object
+    /
+least common multiple of x and y
+[clinic start generated code]*/
+
+static PyObject *
+math_lcm_impl(PyObject *module, PyObject *a, PyObject *b)
+/*[clinic end generated code: output=6f83fb6d671074ba input=efb3d7b7334b7118]*/
+{
+    PyObject *g, *m, *f, *ab;
+
+    a = PyNumber_Index(a);
+    if (a == NULL) {
+        return NULL;
+    }
+    b = PyNumber_Index(b);
+    if (b == NULL) {
+        Py_DECREF(a);
+        return NULL;
+    }
+    if (_PyLong_Sign(a) == 0 || _PyLong_Sign(b) == 0) {
+        Py_DECREF(a);
+        Py_DECREF(b);
+        return PyLong_FromLong(0);
+    }
+    g = _PyLong_GCD(a, b);
+    if (g == NULL) {
+        Py_DECREF(a);
+        Py_DECREF(b);
+        return NULL;
+    }
+    f = PyNumber_FloorDivide(a, g);
+    Py_DECREF(g);
+    Py_DECREF(a);
+    if (f == NULL) {
+        Py_DECREF(b);
+        return NULL;
+    }
+    m = PyNumber_Multiply(f, b);
+    Py_DECREF(f);
+    Py_DECREF(b);
+    if (m == NULL) {
+        return NULL;
+    }
+    ab = PyNumber_Absolute(m);
+    Py_DECREF(m);
+    return ab;
+}
+
+
+/*[clinic input]
 math.trunc
 
     x: object
@@ -3362,6 +3415,7 @@ static PyMethodDef math_methods[] = {
     MATH_ISINF_METHODDEF
     MATH_ISNAN_METHODDEF
     MATH_ISQRT_METHODDEF
+    MATH_LCM_METHODDEF
     MATH_LDEXP_METHODDEF
     {"lgamma",          math_lgamma,    METH_O,         math_lgamma_doc},
     MATH_LOG_METHODDEF