[patch] std::experimental::gcd and std::experimental::lcd

[Jonathan Wakely <jwakely at redhat dot com>]

These where simple to implement (almost too simple ... I probably
got something wrong!)

Tested powerpc64le-linux, committed to trunk.


(Apart from using common_type_t, which is easy to change, these
functions meet the simpler rules for C++11 constexpr, so moving them
out of <experimental/numeric> would probably allow <ratio> to be
greatly simplified. I don't plan on doing that myself any time soon,
but it would make sense to do it some day.)

commit 75a262dbda438434ec7f7ba6144e7e3ca05f5dbc
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Sat May 2 16:02:29 2015 +0100

    	* include/experimental/numeric: New. Define gcd and lcm.
    	* include/Makefile.am: Add new header.
    	* include/Makefile.in: Regenerate.
    	* testsuite/experimental/numeric/gcd.cc: New.
    	* testsuite/experimental/numeric/lcm.cc: New.
    	* doc/xml/manual/status_cxx2017.xml: Update status.
    	* doc/html/manual/status.html: Regenerate.

diff --git a/libstdc++-v3/doc/xml/manual/status_cxx2017.xml b/libstdc++-v3/doc/xml/manual/status_cxx2017.xml
index 80dd050..c30bf09 100644
--- a/libstdc++-v3/doc/xml/manual/status_cxx2017.xml
+++ b/libstdc++-v3/doc/xml/manual/status_cxx2017.xml
@@ -209,14 +209,13 @@ not in any particular release.
     </row>
 
     <row>
-      <?dbhtml bgcolor="#C8B0B0" ?>
       <entry>
 	<link xmlns:xlink="http://www.w3.org/1999/xlink"; xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4061.pdf";>
 	  N4061
 	</link>
       </entry>
       <entry>Greatest Common Divisor and Least Common Multiple</entry>
-      <entry>N</entry>
+      <entry>Y</entry>
       <entry>Library Fundamentals 2 TS</entry>
     </row>
 
diff --git a/libstdc++-v3/include/Makefile.am b/libstdc++-v3/include/Makefile.am
index 6ba702c..92b386a 100644
--- a/libstdc++-v3/include/Makefile.am
+++ b/libstdc++-v3/include/Makefile.am
@@ -654,6 +654,7 @@ experimental_headers = \
 	${experimental_srcdir}/list \
 	${experimental_srcdir}/map \
 	${experimental_srcdir}/memory \
+	${experimental_srcdir}/numeric \
 	${experimental_srcdir}/optional \
 	${experimental_srcdir}/ratio \
 	${experimental_srcdir}/set \
diff --git a/libstdc++-v3/include/experimental/numeric b/libstdc++-v3/include/experimental/numeric
new file mode 100644
index 0000000..a11516b
--- /dev/null
+++ b/libstdc++-v3/include/experimental/numeric
@@ -0,0 +1,88 @@
+// <experimental/numeric> -*- C++ -*-
+
+// Copyright (C) 2015 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// Under Section 7 of GPL version 3, you are granted additional
+// permissions described in the GCC Runtime Library Exception, version
+// 3.1, as published by the Free Software Foundation.
+
+// You should have received a copy of the GNU General Public License and
+// a copy of the GCC Runtime Library Exception along with this program;
+// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+// <http://www.gnu.org/licenses/>.
+
+/** @file experimental/numeric
+ *  This is a TS C++ Library header.
+ */
+
+//
+// N4336 Working Draft, C++ Extensions for Library Fundamentals, Version 2
+//
+
+#ifndef _GLIBCXX_EXPERIMENTAL_NUMERIC
+#define _GLIBCXX_EXPERIMENTAL_NUMERIC 1
+
+#pragma GCC system_header
+
+#if __cplusplus <= 201103L
+# include <bits/c++14_warning.h>
+#else
+
+#include <experimental/type_traits>
+#include <cmath>
+
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+namespace experimental
+{
+inline namespace fundamentals_v2
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+
+#define __cpp_lib_experimental_gcd_lcm 201411
+
+  // Greatest common divisor
+  template<typename _Mn, typename _Nn>
+    constexpr common_type_t<_Mn, _Nn>
+    gcd(_Mn __m, _Nn __n)
+    {
+      static_assert(is_integral<_Mn>::value, "arguments to gcd are integers");
+      static_assert(is_integral<_Nn>::value, "arguments to gcd are integers");
+
+      return __m == 0 ? std::abs(__n)
+	: __n == 0 ? std::abs(__m)
+	: fundamentals_v2::gcd(__n, __m % __n);
+    }
+
+  // Least common multiple
+  template<typename _Mn, typename _Nn>
+    constexpr common_type_t<_Mn, _Nn>
+    lcm(_Mn __m, _Nn __n)
+    {
+      static_assert(is_integral<_Mn>::value, "arguments to lcm are integers");
+      static_assert(is_integral<_Nn>::value, "arguments to lcm are integers");
+
+      return (__m != 0 && __n != 0)
+	? (std::abs(__m) / fundamentals_v2::gcd(__m, __n)) * std::abs(__n)
+	: 0;
+    }
+
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace fundamentals_v2
+} // namespace experimental
+} // namespace std
+
+#endif // __cplusplus <= 201103L
+
+#endif // _GLIBCXX_EXPERIMENTAL_NUMERIC
diff --git a/libstdc++-v3/testsuite/experimental/numeric/gcd.cc b/libstdc++-v3/testsuite/experimental/numeric/gcd.cc
new file mode 100644
index 0000000..efbe273
--- /dev/null
+++ b/libstdc++-v3/testsuite/experimental/numeric/gcd.cc
@@ -0,0 +1,28 @@
+// Copyright (C) 2015 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++14" }
+// { dg-do compile }
+
+#include <experimental/numeric>
+
+using std::experimental::fundamentals_v2::lcm;
+
+static_assert(lcm(21, 6) == 42, "");
+static_assert(lcm(41, 0) == 0, "LCD with zero is zero");
+static_assert(lcm(0, 7) == 0, "LCD with zero is zero");
+static_assert(lcm(0, 0) == 0, "no division by zero");
diff --git a/libstdc++-v3/testsuite/experimental/numeric/lcm.cc b/libstdc++-v3/testsuite/experimental/numeric/lcm.cc
new file mode 100644
index 0000000..359fa09
--- /dev/null
+++ b/libstdc++-v3/testsuite/experimental/numeric/lcm.cc
@@ -0,0 +1,32 @@
+// Copyright (C) 2015 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++14" }
+// { dg-do compile }
+
+#include <experimental/numeric>
+
+using std::experimental::fundamentals_v2::gcd;
+
+static_assert( gcd(1071, 462) == 21, "" );
+static_assert( gcd(2000, 20) == 20, "" );
+static_assert( gcd(2011, 17) == 1, "GCD of two primes is 1" );
+static_assert( gcd(200, 200) == 200, "GCD of equal numbers is that number" );
+static_assert( gcd(0, 13) == 13, "GCD of any number and 0 is that number" );
+static_assert( gcd(29, 0) == 29, "GCD of any number and 0 is that number" );
+static_assert( gcd(0, 0) == 0, "" );
+