From d96f749a5200ac60a1d6819c6accceadf83edcfb Mon Sep 17 00:00:00 2001
From: Hans Dembinski <hans.dembinski@gmail.com>
Date: Wed, 19 Dec 2018 08:50:18 +0100
Subject: [PATCH] deduction guides for histogram

---
 CMakeLists.txt                        |  4 +-
 include/boost/histogram/histogram.hpp | 11 ++++
 test/axis_deduction_guide_test.cpp    | 16 ++++-
 test/deduction_guides_test.cpp        | 87 +++++++++++++++++++++++++++
 4 files changed, 115 insertions(+), 3 deletions(-)
 create mode 100644 test/deduction_guides_test.cpp

diff --git a/CMakeLists.txt b/CMakeLists.txt
index aae1144e..06cd5652 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -145,8 +145,8 @@ if (TEST_RANGE_SUPPORT) # test support for external boost::range
 endif()
 
 if (cxx_std_17 IN_LIST CMAKE_CXX_COMPILE_FEATURES) # test support for optional C++17 features
-  compiled_test(test/axis_deduction_guide_test.cpp)
-  target_compile_features(axis_deduction_guide_test PRIVATE cxx_std_17)
+  compiled_test(test/deduction_guides_test.cpp)
+  target_compile_features(deduction_guides_test PRIVATE cxx_std_17)
 endif()
 
 if (BUILD_BENCHMARKS)
diff --git a/include/boost/histogram/histogram.hpp b/include/boost/histogram/histogram.hpp
index 8f94d67d..efc540a5 100644
--- a/include/boost/histogram/histogram.hpp
+++ b/include/boost/histogram/histogram.hpp
@@ -191,6 +191,17 @@ private:
   friend struct unsafe_access;
 };
 
+#if __cpp_deduction_guides >= 201606
+
+template <class Axes>
+histogram(Axes&& axes)->histogram<detail::unqual<Axes>, default_storage>;
+
+template <class Axes, class Storage>
+histogram(Axes&& axes, Storage&& storage)
+    ->histogram<detail::unqual<Axes>, detail::unqual<Storage>>;
+
+#endif
+
 } // namespace histogram
 } // namespace boost
 
diff --git a/test/axis_deduction_guide_test.cpp b/test/axis_deduction_guide_test.cpp
index aaf2cfff..1fc75169 100644
--- a/test/axis_deduction_guide_test.cpp
+++ b/test/axis_deduction_guide_test.cpp
@@ -6,8 +6,9 @@
 
 #include <boost/core/lightweight_test.hpp>
 #include <boost/core/lightweight_test_trait.hpp>
-#include <boost/histogram/axis.hpp>
+#include <boost/histogram.hpp>
 #include <boost/histogram/axis/ostream_operators.hpp>
+#include <boost/histogram/ostream_operators.hpp>
 #include <type_traits>
 
 using namespace boost::histogram;
@@ -82,6 +83,19 @@ int main() {
     BOOST_TEST_TRAIT_TRUE(
         (std::is_same<decltype(i), axis::variable<double, axis::null_type>>));
   }
+
+  {
+    auto a = histogram(std::make_tuple(axis::regular(3, -1, 1), axis::integer(0, 4)));
+    BOOST_TEST_EQ(a.rank(), 2);
+    BOOST_TEST_EQ(a.axis(0), axis::regular(3, -1, 1));
+    BOOST_TEST_EQ(a.axis(1), axis::integer(0, 4));
+
+    std::vector<axis::regular<>> axes{{axis::regular(3, -1, 1), axis::regular(5, 0, 5)}};
+    auto b = histogram(axes, weighted_storage());
+    BOOST_TEST_EQ(b.rank(), 2);
+    BOOST_TEST_EQ(b.axis(0), axis::regular(3, -1, 1));
+    BOOST_TEST_EQ(b.axis(1), axis::regular(5, 0, 5));
+  }
 #endif
   return boost::report_errors();
 }
diff --git a/test/deduction_guides_test.cpp b/test/deduction_guides_test.cpp
new file mode 100644
index 00000000..aaf2cfff
--- /dev/null
+++ b/test/deduction_guides_test.cpp
@@ -0,0 +1,87 @@
+// Copyright 2018 Hans Dembinski
+//
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt
+// or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#include <boost/core/lightweight_test.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <boost/histogram/axis.hpp>
+#include <boost/histogram/axis/ostream_operators.hpp>
+#include <type_traits>
+
+using namespace boost::histogram;
+namespace tr = axis::transform;
+
+// tests requires a C++17 compatible compiler
+
+int main() {
+#if __cpp_deduction_guides >= 201611
+  {
+    axis::regular a(1, 0.0, 1.0);
+    axis::regular b(1, 0, 1);
+    axis::regular c(1, 0.0f, 1.0f);
+    axis::regular d(1, 0, 1, "foo");
+    axis::regular e(1, 0, 1, axis::null_type{});
+    axis::regular f(tr::sqrt(), 1, 0, 1);
+    axis::regular g(tr::sqrt(), 1, 0, 1, "foo");
+    axis::regular h(tr::sqrt(), 1, 0, 1, axis::null_type{});
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<decltype(a), axis::regular<>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<decltype(b), axis::regular<>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<decltype(c), axis::regular<float>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<decltype(d), axis::regular<>>));
+    BOOST_TEST_TRAIT_TRUE(
+        (std::is_same<decltype(e), axis::regular<double, tr::id, axis::null_type>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<decltype(f), axis::regular<double, tr::sqrt>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<decltype(g), axis::regular<double, tr::sqrt>>));
+    BOOST_TEST_TRAIT_TRUE(
+        (std::is_same<decltype(h), axis::regular<double, tr::sqrt, axis::null_type>>));
+  }
+
+  {
+    axis::integer a(1, 2);
+    axis::integer b(1l, 2l);
+    axis::integer c(1.0, 2.0);
+    axis::integer d(1.0f, 2.0f);
+    axis::integer e(1, 2, "foo");
+    axis::integer f(1, 2, axis::null_type{});
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<decltype(a), axis::integer<int>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<decltype(b), axis::integer<int>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<decltype(c), axis::integer<double>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<decltype(d), axis::integer<float>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<decltype(e), axis::integer<int>>));
+    BOOST_TEST_TRAIT_TRUE(
+        (std::is_same<decltype(f), axis::integer<int, axis::null_type>>));
+  }
+
+  {
+    axis::variable a{-1, 1};
+    axis::variable b{-1.f, 1.f};
+    axis::variable c{-1.0, 1.0};
+    axis::variable d({-1, 1}, "foo");
+    axis::variable e({-1, 1}, axis::null_type{});
+
+    std::vector<int> vi{{-1, 1}};
+    std::vector<float> vf{{-1.f, 1.f}};
+    axis::variable f(vi);
+    axis::variable g(vf);
+    axis::variable h(vi, "foo");
+    axis::variable i(vi, axis::null_type{});
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<decltype(a), axis::variable<>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<decltype(b), axis::variable<float>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<decltype(c), axis::variable<>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<decltype(d), axis::variable<>>));
+    BOOST_TEST_TRAIT_TRUE(
+        (std::is_same<decltype(e), axis::variable<double, axis::null_type>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<decltype(f), axis::variable<>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<decltype(g), axis::variable<float>>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<decltype(h), axis::variable<>>));
+    BOOST_TEST_TRAIT_TRUE(
+        (std::is_same<decltype(i), axis::variable<double, axis::null_type>>));
+  }
+#endif
+  return boost::report_errors();
+}