Add class template argument deduction guides for distributions (#756)

* Demonstrate deduction guides for normal_distribution.

* Add missing test case.

* add class template argument deduction guides for distributions templated on real type - issue #754

* Remove no-arg tests in test_dist_deduction_guides.cpp - issue #754

GCC-8 and clang 6-8 were unhappy with the no-arg cases, which use the
default template arg, not the deduction guide, anyway.

* remove unused deduction guide for fisher_f - issue #754

Co-authored-by: jzmaddock <john@johnmaddock.co.uk>

include/boost/math/distributions/arcsine.hpp

@@ -194,6 +194,12 @@ namespace boost
     // Convenient typedef to construct double version.
     typedef arcsine_distribution<double> arcsine;
 
+    #ifdef __cpp_deduction_guides
+    template <class RealType>
+    arcsine_distribution(RealType)->arcsine_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+    template <class RealType>
+    arcsine_distribution(RealType, RealType)->arcsine_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+    #endif
 
     template <class RealType, class Policy>
     inline const std::pair<RealType, RealType> range(const arcsine_distribution<RealType, Policy>&  dist)

include/boost/math/distributions/bernoulli.hpp

@@ -126,6 +126,11 @@ namespace boost
 
     typedef bernoulli_distribution<double> bernoulli;
 
+    #ifdef __cpp_deduction_guides
+    template <class RealType>
+    bernoulli_distribution(RealType)->bernoulli_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+    #endif
+
     template <class RealType, class Policy>
     inline const std::pair<RealType, RealType> range(const bernoulli_distribution<RealType, Policy>& /* dist */)
     { // Range of permissible values for random variable k = {0, 1}.

include/boost/math/distributions/beta.hpp

@@ -272,6 +272,13 @@ namespace boost
       RealType m_beta;
     }; // template <class RealType, class Policy> class beta_distribution
 
+    #ifdef __cpp_deduction_guides
+    template <class RealType>
+    beta_distribution(RealType)->beta_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+    template <class RealType>
+    beta_distribution(RealType, RealType)->beta_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+    #endif
+
     template <class RealType, class Policy>
     inline const std::pair<RealType, RealType> range(const beta_distribution<RealType, Policy>& /* dist */)
     { // Range of permissible values for random variable x.

include/boost/math/distributions/binomial.hpp

@@ -414,6 +414,13 @@ namespace boost
       // IS now included since no longer a name clash with function binomial.
       //typedef binomial_distribution<double> binomial; // Reserved name of type double.
 
+      #ifdef __cpp_deduction_guides
+      template <class RealType>
+      binomial_distribution(RealType)->binomial_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+      template <class RealType>
+      binomial_distribution(RealType,RealType)->binomial_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+      #endif
+
       template <class RealType, class Policy>
       const std::pair<RealType, RealType> range(const binomial_distribution<RealType, Policy>& dist)
       { // Range of permissible values for random variable k.

include/boost/math/distributions/cauchy.hpp

@@ -176,6 +176,13 @@ class cauchy_distribution
 
 typedef cauchy_distribution<double> cauchy;
 
+#ifdef __cpp_deduction_guides
+template <class RealType>
+cauchy_distribution(RealType)->cauchy_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+template <class RealType>
+cauchy_distribution(RealType,RealType)->cauchy_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+#endif
+
 template <class RealType, class Policy>
 inline const std::pair<RealType, RealType> range(const cauchy_distribution<RealType, Policy>&)
 { // Range of permissible values for random variable x.

include/boost/math/distributions/chi_squared.hpp

@@ -55,6 +55,11 @@ class chi_squared_distribution
 
 typedef chi_squared_distribution<double> chi_squared;
 
+#ifdef __cpp_deduction_guides
+template <class RealType>
+chi_squared_distribution(RealType)->chi_squared_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+#endif
+
 #ifdef _MSC_VER
 #pragma warning(push)
 #pragma warning(disable:4127)

include/boost/math/distributions/exponential.hpp

@@ -78,6 +78,11 @@ class exponential_distribution
 
 typedef exponential_distribution<double> exponential;
 
+#ifdef __cpp_deduction_guides
+template <class RealType>
+exponential_distribution(RealType)->exponential_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+#endif
+
 template <class RealType, class Policy>
 inline const std::pair<RealType, RealType> range(const exponential_distribution<RealType, Policy>& /*dist*/)
 { // Range of permissible values for random variable x.

include/boost/math/distributions/extreme_value.hpp

@@ -73,6 +73,13 @@ class extreme_value_distribution
 
 typedef extreme_value_distribution<double> extreme_value;
 
+#ifdef __cpp_deduction_guides
+template <class RealType>
+extreme_value_distribution(RealType)->extreme_value_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+template <class RealType>
+extreme_value_distribution(RealType,RealType)->extreme_value_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+#endif
+
 template <class RealType, class Policy>
 inline const std::pair<RealType, RealType> range(const extreme_value_distribution<RealType, Policy>& /*dist*/)
 { // Range of permissible values for random variable x.

include/boost/math/distributions/fisher_f.hpp

@@ -54,6 +54,11 @@ class fisher_f_distribution
 
 typedef fisher_f_distribution<double> fisher_f;
 
+#ifdef __cpp_deduction_guides
+template <class RealType>
+fisher_f_distribution(RealType,RealType)->fisher_f_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+#endif
+
 template <class RealType, class Policy>
 inline const std::pair<RealType, RealType> range(const fisher_f_distribution<RealType, Policy>& /*dist*/)
 { // Range of permissible values for random variable x.

include/boost/math/distributions/gamma.hpp

@@ -100,6 +100,13 @@ class gamma_distribution
 
 // NO typedef because of clash with name of gamma function.
 
+#ifdef __cpp_deduction_guides
+template <class RealType>
+gamma_distribution(RealType)->gamma_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+template <class RealType>
+gamma_distribution(RealType,RealType)->gamma_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+#endif
+
 template <class RealType, class Policy>
 inline const std::pair<RealType, RealType> range(const gamma_distribution<RealType, Policy>& /* dist */)
 { // Range of permissible values for random variable x.

include/boost/math/distributions/geometric.hpp

@@ -236,6 +236,11 @@ namespace boost
 
     typedef geometric_distribution<double> geometric; // Reserved name of type double.
 
+    #ifdef __cpp_deduction_guides
+    template <class RealType>
+    geometric_distribution(RealType)->geometric_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+    #endif
+
     template <class RealType, class Policy>
     inline const std::pair<RealType, RealType> range(const geometric_distribution<RealType, Policy>& /* dist */)
     { // Range of permissible values for random variable k.

include/boost/math/distributions/inverse_chi_squared.hpp

@@ -97,6 +97,13 @@ class inverse_chi_squared_distribution
 
 typedef inverse_chi_squared_distribution<double> inverse_chi_squared;
 
+#ifdef __cpp_deduction_guides
+template <class RealType>
+inverse_chi_squared_distribution(RealType)->inverse_chi_squared_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+template <class RealType>
+inverse_chi_squared_distribution(RealType,RealType)->inverse_chi_squared_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+#endif
+
 template <class RealType, class Policy>
 inline const std::pair<RealType, RealType> range(const inverse_chi_squared_distribution<RealType, Policy>& /*dist*/)
 {  // Range of permissible values for random variable x.

include/boost/math/distributions/inverse_gamma.hpp

@@ -122,6 +122,13 @@ typedef inverse_gamma_distribution<double> inverse_gamma;
 // but there is a typedef for gamma
 //   typedef boost::math::gamma_distribution<Type, Policy> gamma;
 
+#ifdef __cpp_deduction_guides
+template <class RealType>
+inverse_gamma_distribution(RealType)->inverse_gamma_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+template <class RealType>
+inverse_gamma_distribution(RealType,RealType)->inverse_gamma_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+#endif
+
 // Allow random variable x to be zero, treated as a special case (unlike some definitions).
 
 template <class RealType, class Policy>

include/boost/math/distributions/inverse_gaussian.hpp

@@ -115,6 +115,13 @@ class inverse_gaussian_distribution
 
 typedef inverse_gaussian_distribution<double> inverse_gaussian;
 
+#ifdef __cpp_deduction_guides
+template <class RealType>
+inverse_gaussian_distribution(RealType)->inverse_gaussian_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+template <class RealType>
+inverse_gaussian_distribution(RealType,RealType)->inverse_gaussian_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+#endif
+
 template <class RealType, class Policy>
 inline const std::pair<RealType, RealType> range(const inverse_gaussian_distribution<RealType, Policy>& /*dist*/)
 { // Range of permissible values for random variable x, zero to max.

include/boost/math/distributions/kolmogorov_smirnov.hpp

@@ -213,6 +213,11 @@ template <class RealType = double, class Policy = policies::policy<> >
 
 typedef kolmogorov_smirnov_distribution<double> kolmogorov_k; // Convenience typedef for double version.
 
+#ifdef __cpp_deduction_guides
+template <class RealType>
+kolmogorov_smirnov_distribution(RealType)->kolmogorov_smirnov_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+#endif
+
 namespace detail {
 template <class RealType, class Policy>
 struct kolmogorov_smirnov_quantile_functor

include/boost/math/distributions/laplace.hpp

@@ -80,6 +80,13 @@ class laplace_distribution
 // Convenient type synonym for double.
 typedef laplace_distribution<double> laplace;
 
+#ifdef __cpp_deduction_guides
+template <class RealType>
+laplace_distribution(RealType)->laplace_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+template <class RealType>
+laplace_distribution(RealType,RealType)->laplace_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+#endif
+
 //
 // Non-member functions.
 template <class RealType, class Policy>

include/boost/math/distributions/logistic.hpp

@@ -51,7 +51,14 @@ namespace boost { namespace math {
 
 
     typedef logistic_distribution<double> logistic;
-
+
+    #ifdef __cpp_deduction_guides
+    template <class RealType>
+    logistic_distribution(RealType)->logistic_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+    template <class RealType>
+    logistic_distribution(RealType,RealType)->logistic_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+    #endif
+
     template <class RealType, class Policy>
     inline const std::pair<RealType, RealType> range(const logistic_distribution<RealType, Policy>& /* dist */)
     { // Range of permissible values for random variable x.

include/boost/math/distributions/lognormal.hpp

@@ -75,6 +75,13 @@ class lognormal_distribution
 
 typedef lognormal_distribution<double> lognormal;
 
+#ifdef __cpp_deduction_guides
+template <class RealType>
+lognormal_distribution(RealType)->lognormal_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+template <class RealType>
+lognormal_distribution(RealType,RealType)->lognormal_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+#endif
+
 template <class RealType, class Policy>
 inline const std::pair<RealType, RealType> range(const lognormal_distribution<RealType, Policy>& /*dist*/)
 { // Range of permissible values for random variable x is >0 to +infinity.

include/boost/math/distributions/negative_binomial.hpp

@@ -251,6 +251,11 @@ namespace boost
 
     typedef negative_binomial_distribution<double> negative_binomial; // Reserved name of type double.
 
+    #ifdef __cpp_deduction_guides
+    template <class RealType>
+    negative_binomial_distribution(RealType,RealType)->negative_binomial_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+    #endif
+
     template <class RealType, class Policy>
     inline const std::pair<RealType, RealType> range(const negative_binomial_distribution<RealType, Policy>& /* dist */)
     { // Range of permissible values for random variable k.

include/boost/math/distributions/non_central_beta.hpp

@@ -707,6 +707,11 @@ namespace boost
 
       typedef non_central_beta_distribution<double> non_central_beta; // Reserved name of type double.
 
+      #ifdef __cpp_deduction_guides
+      template <class RealType>
+      non_central_beta_distribution(RealType,RealType,RealType)->non_central_beta_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+      #endif
+
       // Non-member functions to give properties of the distribution.
 
       template <class RealType, class Policy>

include/boost/math/distributions/non_central_chi_squared.hpp

@@ -783,6 +783,11 @@ namespace boost
 
       typedef non_central_chi_squared_distribution<double> non_central_chi_squared; // Reserved name of type double.
 
+      #ifdef __cpp_deduction_guides
+      template <class RealType>
+      non_central_chi_squared_distribution(RealType,RealType)->non_central_chi_squared_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+      #endif
+
       // Non-member functions to give properties of the distribution.
 
       template <class RealType, class Policy>

include/boost/math/distributions/non_central_f.hpp

@@ -63,6 +63,11 @@ namespace boost
 
       typedef non_central_f_distribution<double> non_central_f; // Reserved name of type double.
 
+      #ifdef __cpp_deduction_guides
+      template <class RealType>
+      non_central_f_distribution(RealType,RealType,RealType)->non_central_f_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+      #endif
+
       // Non-member functions to give properties of the distribution.
 
       template <class RealType, class Policy>

include/boost/math/distributions/non_central_t.hpp

@@ -838,6 +838,11 @@ namespace boost
 
       typedef non_central_t_distribution<double> non_central_t; // Reserved name of type double.
 
+      #ifdef __cpp_deduction_guides
+      template <class RealType>
+      non_central_t_distribution(RealType,RealType)->non_central_t_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+      #endif
+
       // Non-member functions to give properties of the distribution.
 
       template <class RealType, class Policy>

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)

include/boost/math/distributions/pareto.hpp

@@ -160,6 +160,14 @@ namespace boost
 
     typedef pareto_distribution<double> pareto; // Convenience to allow pareto(2., 3.);
 
+    #ifdef __cpp_deduction_guides
+    template <class RealType>
+    pareto_distribution(RealType)->pareto_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+    template <class RealType>
+    pareto_distribution(RealType,RealType)->pareto_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+    #endif
+
+
     template <class RealType, class Policy>
     inline const std::pair<RealType, RealType> range(const pareto_distribution<RealType, Policy>& /*dist*/)
     { // Range of permissible values for random variable x.

include/boost/math/distributions/poisson.hpp

@@ -167,6 +167,11 @@ namespace boost
 
     typedef poisson_distribution<double> poisson; // Reserved name of type double.
 
+    #ifdef __cpp_deduction_guides
+    template <class RealType>
+    poisson_distribution(RealType)->poisson_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+    #endif
+
     // Non-member functions to give properties of the distribution.
 
     template <class RealType, class Policy>

include/boost/math/distributions/rayleigh.hpp

@@ -77,6 +77,11 @@ class rayleigh_distribution
 
 typedef rayleigh_distribution<double> rayleigh;
 
+#ifdef __cpp_deduction_guides
+template <class RealType>
+rayleigh_distribution(RealType)->rayleigh_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+#endif
+
 template <class RealType, class Policy>
 inline const std::pair<RealType, RealType> range(const rayleigh_distribution<RealType, Policy>& /*dist*/)
 { // Range of permissible values for random variable x.

include/boost/math/distributions/skew_normal.hpp

@@ -96,6 +96,15 @@ namespace boost{ namespace math{
 
   typedef skew_normal_distribution<double> skew_normal;
 
+  #ifdef __cpp_deduction_guides
+  template <class RealType>
+  skew_normal_distribution(RealType)->skew_normal_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+  template <class RealType>
+  skew_normal_distribution(RealType,RealType)->skew_normal_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+  template <class RealType>
+  skew_normal_distribution(RealType,RealType,RealType)->skew_normal_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+  #endif
+
   template <class RealType, class Policy>
   inline const std::pair<RealType, RealType> range(const skew_normal_distribution<RealType, Policy>& /*dist*/)
   { // Range of permissible values for random variable x.

include/boost/math/distributions/students_t.hpp

@@ -62,6 +62,11 @@ class students_t_distribution
 
 typedef students_t_distribution<double> students_t; // Convenience typedef for double version.
 
+#ifdef __cpp_deduction_guides
+template <class RealType>
+students_t_distribution(RealType)->students_t_distribution<typename boost::math::tools::promote_args<RealType>::type>;
+#endif
+
 template <class RealType, class Policy>
 inline const std::pair<RealType, RealType> range(const students_t_distribution<RealType, Policy>& /*dist*/)
 { // Range of permissible values for random variable x.