From 2113258e86961517348d908d90f5cbe6c8f4c6f3 Mon Sep 17 00:00:00 2001
From: jzmaddock <john@johnmaddock.co.uk>
Date: Wed, 2 Feb 2022 19:24:24 +0000
Subject: [PATCH 1/2] Demonstrate deduction guides for normal_distribution.

---
 include/boost/math/distributions/normal.hpp | 14 ++++++++++++++
 test/Jamfile.v2                             |  2 ++
 2 files changed, 16 insertions(+)

diff --git a/include/boost/math/distributions/normal.hpp b/include/boost/math/distributions/normal.hpp
index b9697ebb08..73ada53b6f 100644
--- a/include/boost/math/distributions/normal.hpp
+++ b/include/boost/math/distributions/normal.hpp
@@ -71,6 +71,20 @@ class normal_distribution
 
 typedef normal_distribution<double> normal;
 
+//
+// Deduction guides, note we don't check the 
+// value of __cpp_deduction_guides, just assume
+// they work as advertised, even if this is pre-final C++17.
+//
+#ifdef __cpp_deduction_guides
+
+template <class RealType>
+normal_distribution(RealType, RealType)->normal_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+template <class RealType>
+normal_distribution(RealType)->normal_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+
+#endif
+
 #ifdef _MSC_VER
 #pragma warning(push)
 #pragma warning(disable:4127)
diff --git a/test/Jamfile.v2 b/test/Jamfile.v2
index 6d5667a295..828f22663b 100644
--- a/test/Jamfile.v2
+++ b/test/Jamfile.v2
@@ -877,6 +877,8 @@ test-suite distribution_tests :
    [ run test_signed_zero.cpp ../../test/build//boost_unit_test_framework  ]
    [ run complex_test.cpp ../../test/build//boost_unit_test_framework  ]
 
+   [ compile test_normal_dist_deduction_guides.cpp : [ requires cpp_deduction_guides ] ]
+
 ;
 
 test-suite mp :

From 50434445a4367651eb1f525840e317051537b2c0 Mon Sep 17 00:00:00 2001
From: jzmaddock <john@johnmaddock.co.uk>
Date: Wed, 2 Feb 2022 19:28:53 +0000
Subject: [PATCH 2/2] Add missing test case.

---
 test/test_normal_dist_deduction_guides.cpp | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
 create mode 100644 test/test_normal_dist_deduction_guides.cpp

diff --git a/test/test_normal_dist_deduction_guides.cpp b/test/test_normal_dist_deduction_guides.cpp
new file mode 100644
index 0000000000..baa4ffb220
--- /dev/null
+++ b/test/test_normal_dist_deduction_guides.cpp
@@ -0,0 +1,18 @@
+//  (C) Copyright John Maddock 2022.
+//  Use, modification and distribution are subject to 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/math/distributions/normal.hpp>
+
+int main()
+{
+   using namespace boost::math;
+
+   normal_distribution n;
+   static_assert(std::is_same<decltype(n)::value_type, double>::value);
+   normal_distribution n2(2);
+   static_assert(std::is_same<decltype(n2)::value_type, double>::value);
+   normal_distribution n3(2, 3);
+   static_assert(std::is_same<decltype(n3)::value_type, double>::value);
+}