From c98cace988e9fc49c1234a93f324930353521f2d Mon Sep 17 00:00:00 2001
From: Daniel Arndt <daniel.arndt@iwr.uni-heidelberg.de>
Date: Mon, 31 Jul 2017 00:13:09 +0200
Subject: [PATCH] Implement constexpr max and min for DEAL_II_WITH_CXX14=false

---
 include/deal.II/base/patterns.h              | 10 ++--
 include/deal.II/base/std_cxx14/algorithm.h   | 60 ++++++++++++++++++++
 tests/base/stdcxx14_constexpr_min_max.cc     | 51 +++++++++++++++++
 tests/base/stdcxx14_constexpr_min_max.output |  6 ++
 4 files changed, 122 insertions(+), 5 deletions(-)
 create mode 100644 include/deal.II/base/std_cxx14/algorithm.h
 create mode 100644 tests/base/stdcxx14_constexpr_min_max.cc
 create mode 100644 tests/base/stdcxx14_constexpr_min_max.output

diff --git a/include/deal.II/base/patterns.h b/include/deal.II/base/patterns.h
index c5d0c4e015..69c8441b14 100644
--- a/include/deal.II/base/patterns.h
+++ b/include/deal.II/base/patterns.h
@@ -24,7 +24,7 @@
 #include <deal.II/base/std_cxx14/memory.h>
 #include <deal.II/base/subscriptor.h>
 #include <deal.II/base/utilities.h>
-
+#include <deal.II/base/std_cxx14/algorithm.h>
 
 #include <boost/archive/basic_archive.hpp>
 #include <boost/core/demangle.hpp>
@@ -1270,12 +1270,12 @@ namespace Patterns
       struct RankInfo<T, typename std::enable_if<is_map_compatible<T>::value>::type>
       {
         static constexpr int list_rank =
-          std::max(internal::RankInfo<typename T::key_type>::list_rank,
-                   RankInfo<typename T::mapped_type>::list_rank) +
+          std_cxx14::max(internal::RankInfo<typename T::key_type>::list_rank,
+                         RankInfo<typename T::mapped_type>::list_rank) +
           1;
         static constexpr int map_rank =
-          std::max(internal::RankInfo<typename T::key_type>::map_rank,
-                   RankInfo<typename T::mapped_type>::map_rank) +
+          std_cxx14::max(internal::RankInfo<typename T::key_type>::map_rank,
+                         RankInfo<typename T::mapped_type>::map_rank) +
           1;
       };
 
diff --git a/include/deal.II/base/std_cxx14/algorithm.h b/include/deal.II/base/std_cxx14/algorithm.h
new file mode 100644
index 0000000000..a644f32d45
--- /dev/null
+++ b/include/deal.II/base/std_cxx14/algorithm.h
@@ -0,0 +1,60 @@
+// ---------------------------------------------------------------------
+//
+// Copyright (C) 2017 by the deal.II authors
+//
+// This file is part of the deal.II library.
+//
+// The deal.II library is free software; you can use it, redistribute
+// it, and/or modify it under the terms of the GNU Lesser General
+// Public License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+// The full text of the license can be found in the file LICENSE at
+// the top level of the deal.II distribution.
+//
+// ---------------------------------------------------------------------
+#ifndef dealii__cxx14_algorithm_h
+#define dealii__cxx14_algorithm_h
+
+#include <deal.II/base/config.h>
+
+#ifdef DEAL_II_WITH_CXX14
+#include <algorithm>
+#endif
+
+DEAL_II_NAMESPACE_OPEN
+namespace std_cxx14
+{
+#ifdef DEAL_II_WITH_CXX14
+  using std::max;
+  using std::min;
+#else
+
+  template<class T>
+  constexpr const T &max(const T &a, const T &b)
+  {
+    return (a < b) ? b : a;
+  }
+
+  template<class T, class Compare>
+  constexpr const T &max(const T &a, const T &b, Compare comp)
+  {
+    return (comp(a, b)) ? b : a;
+  }
+
+  template<class T>
+  constexpr const T &min(const T &a, const T &b)
+  {
+    return (b < a) ? b : a;
+  }
+
+  template<class T, class Compare>
+  constexpr const T &min(const T &a, const T &b, Compare comp)
+  {
+    return (comp(b, a)) ? b : a;
+  }
+
+#endif
+}
+DEAL_II_NAMESPACE_CLOSE
+
+#endif // dealii__cxx14_algorithm_h
diff --git a/tests/base/stdcxx14_constexpr_min_max.cc b/tests/base/stdcxx14_constexpr_min_max.cc
new file mode 100644
index 0000000000..0eb37376c2
--- /dev/null
+++ b/tests/base/stdcxx14_constexpr_min_max.cc
@@ -0,0 +1,51 @@
+// ---------------------------------------------------------------------
+//
+// Copyright (C) 2017 by the deal.II authors
+//
+// This file is part of the deal.II library.
+//
+// The deal.II library is free software; you can use it, redistribute
+// it, and/or modify it under the terms of the GNU Lesser General
+// Public License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+// The full text of the license can be found in the file LICENSE at
+// the top level of the deal.II distribution.
+//
+// ---------------------------------------------------------------------
+
+
+// test the implementation of theh constexpr min/max functions
+// in case deal.II is compiled with C++14 support, we only test
+// the STL.
+
+
+#include "../tests.h"
+#include <deal.II/base/std_cxx14/algorithm.h>
+#include <deal.II/base/logstream.h>
+#include <fstream>
+#include <iomanip>
+
+constexpr bool comp (const int &a, const int &b)
+{
+  return b<a;
+}
+
+
+int main ()
+{
+  initlog();
+  deallog.threshold_double(1.e-10);
+
+  constexpr int max_1 = std_cxx14::max(0,1);
+  deallog << max_1 << std::endl;
+  constexpr int max_2 = std_cxx14::max(3,2,comp);
+  deallog << max_2 << std::endl;
+
+  constexpr int min_1 = std_cxx14::min(1,2);
+  deallog << min_1 << std::endl;
+  constexpr int min_2 = std_cxx14::min(1,2,comp);
+  deallog << min_2 << std::endl;
+
+  deallog << "OK" << std::endl;
+}
+
diff --git a/tests/base/stdcxx14_constexpr_min_max.output b/tests/base/stdcxx14_constexpr_min_max.output
new file mode 100644
index 0000000000..c264dc89a9
--- /dev/null
+++ b/tests/base/stdcxx14_constexpr_min_max.output
@@ -0,0 +1,6 @@
+
+DEAL::1
+DEAL::2
+DEAL::1
+DEAL::2
+DEAL::OK
-- 
2.39.5