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Implement N3887: std::tuple_element_t

Message ID 20140414231819.GH6807@redhat.com
State New
Headers show

Commit Message

Jonathan Wakely April 14, 2014, 11:18 p.m. UTC 
This adds the std::tuple_element_t alias template for C++14.

Tested x86_64-linux, committed to trunk.
commit 8aed2fc56f7bbd765e79f6c88e50c19e195e32ac
Author: Jonathan Wakely <accu@kayari.org>
Date:   Mon Apr 14 16:36:00 2014 +0100

    N3887 Consistent Metafunction Aliases
    
    	* include/std/tuple (tuple_element_t): Define.
    	* testsuite/20_util/tuple/tuple_element.cc: Change to compile-only
    	test.
    	* testsuite/20_util/tuple/tuple_element_t.cc: New.
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Patch

diff --git a/libstdc++-v3/include/std/tuple b/libstdc++-v3/include/std/tuple
index 47a10ec..03d87d7 100644
--- a/libstdc++-v3/include/std/tuple
+++ b/libstdc++-v3/include/std/tuple
@@ -710,6 +710,11 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
       add_cv<typename tuple_element<__i, _Tp>::type>::type type;
     };
 
+#if __cplusplus > 201103L
+  template<std::size_t __i, typename _Tp>
+    using tuple_element_t = typename tuple_element<__i, _Tp>::type;
+#endif
+
   /// Finds the size of a given tuple type.
   template<typename _Tp>
     struct tuple_size;
diff --git a/libstdc++-v3/testsuite/20_util/tuple/tuple_element.cc b/libstdc++-v3/testsuite/20_util/tuple/tuple_element.cc
index 0dbdf10..3ff8e82 100644
--- a/libstdc++-v3/testsuite/20_util/tuple/tuple_element.cc
+++ b/libstdc++-v3/testsuite/20_util/tuple/tuple_element.cc
@@ -1,4 +1,5 @@ 
-// { dg-options "-std=gnu++0x" }
+// { dg-options "-std=gnu++11" }
+// { dg-do compile }
 
 // Copyright (C) 2007-2014 Free Software Foundation, Inc.
 //
diff --git a/libstdc++-v3/testsuite/20_util/tuple/tuple_element_t.cc b/libstdc++-v3/testsuite/20_util/tuple/tuple_element_t.cc
new file mode 100644
index 0000000..e46af5c
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/tuple/tuple_element_t.cc
@@ -0,0 +1,36 @@ 
+// { dg-options "-std=gnu++14" }
+// { dg-do compile }
+
+// Copyright (C) 2014 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/>.
+
+#include <tuple>
+
+using namespace std;
+
+struct foo
+{ };
+
+int
+main()
+{
+  // As foo isn't constructible from anything else, this
+  // lets us check if the alias is returning foo when it should
+  foo q1;
+  tuple_element_t<0,tuple<foo,void,int> > q2(q1);
+  tuple_element_t<2,tuple<void,int,foo> > q3(q1);
+}