Assert when features which require C++17 are compiled for an earlier C++ version.

Also document C++17 requirement for norms.

doc/vector_functionals/norms.qbk

@@ -8,6 +8,8 @@
 
 [section:norms Norms]
 
+[note All of the functions below require at least C++17]
+
 [heading Synopsis]
 
 ``

include/boost/math/ccmath/abs.hpp

@@ -15,6 +15,14 @@
 #include <boost/math/ccmath/isnan.hpp>
 #include <boost/math/ccmath/isinf.hpp>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 namespace boost::math::ccmath {
 
 namespace detail {

include/boost/math/ccmath/div.hpp

@@ -12,6 +12,14 @@
 #include <cstdint>
 #include <type_traits>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 namespace boost::math::ccmath {
 
 namespace detail {

include/boost/math/ccmath/fma.hpp

@@ -13,6 +13,14 @@
 #include <boost/math/ccmath/isinf.hpp>
 #include <boost/math/ccmath/isnan.hpp>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 namespace boost::math::ccmath {
 
 namespace detail {

include/boost/math/ccmath/isfinite.hpp

@@ -12,6 +12,14 @@
 #include <boost/math/ccmath/isinf.hpp>
 #include <boost/math/ccmath/isnan.hpp>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 namespace boost::math::ccmath {
 
 template <typename T>

include/boost/math/ccmath/isinf.hpp

@@ -11,6 +11,14 @@
 #include <type_traits>
 #include <boost/math/tools/is_constant_evaluated.hpp>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 namespace boost::math::ccmath {
 
 template <typename T>

include/boost/math/ccmath/isnan.hpp

@@ -10,6 +10,14 @@
 #include <type_traits>
 #include <boost/math/tools/is_constant_evaluated.hpp>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 namespace boost::math::ccmath {
 
 template <typename T>

include/boost/math/ccmath/isnormal.hpp

@@ -14,6 +14,14 @@
 #include <boost/math/ccmath/isinf.hpp>
 #include <boost/math/ccmath/isnan.hpp>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 namespace boost::math::ccmath {
 
 template <typename T>

include/boost/math/ccmath/round.hpp

@@ -15,6 +15,14 @@
 #include <boost/math/ccmath/isnan.hpp>
 #include <boost/math/ccmath/modf.hpp>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 namespace boost::math::ccmath {
 
 namespace detail {

include/boost/math/ccmath/signbit.hpp

@@ -16,6 +16,14 @@
 #include <boost/math/ccmath/isnan.hpp>
 #include <boost/math/ccmath/abs.hpp>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 #ifdef __has_include
 #  if __has_include(<bit>)
 #    include <bit>

include/boost/math/differentiation/lanczos_smoothing.hpp

@@ -14,6 +14,14 @@
 #include <type_traits>
 #include <boost/math/tools/assert.hpp>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 namespace boost::math::differentiation {
 
 namespace detail {

include/boost/math/distributions/empirical_cumulative_distribution_function.hpp

@@ -11,6 +11,14 @@
 #include <type_traits>
 #include <utility>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 namespace boost { namespace math{
 
 template<class RandomAccessContainer>

include/boost/math/filters/daubechies.hpp

@@ -10,6 +10,14 @@
 #include <limits>
 #include <boost/math/tools/big_constant.hpp>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 namespace boost::math::filters {
 
 template <typename Real, unsigned p>

include/boost/math/special_functions/daubechies_scaling.hpp

@@ -19,6 +19,14 @@
 #include <boost/math/interpolators/detail/quintic_hermite_detail.hpp>
 #include <boost/math/interpolators/detail/septic_hermite_detail.hpp>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 namespace boost::math {
 
 template<class Real, int p, int order>

include/boost/math/special_functions/daubechies_wavelet.hpp

@@ -21,6 +21,14 @@
 #include <boost/math/interpolators/detail/quintic_hermite_detail.hpp>
 #include <boost/math/interpolators/detail/septic_hermite_detail.hpp>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 namespace boost::math {
 
    template<class Real, int p, int order>

include/boost/math/special_functions/rsqrt.hpp

@@ -9,6 +9,14 @@
 #include <type_traits>
 #include <limits>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 namespace boost::math {
 
 template<typename Real>

include/boost/math/statistics/signal_statistics.hpp

@@ -13,6 +13,13 @@
 #include <boost/math/tools/roots.hpp>
 #include <boost/math/statistics/univariate_statistics.hpp>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
 
 namespace boost::math::statistics {
 

include/boost/math/tools/centered_continued_fraction.hpp

@@ -18,6 +18,13 @@
 #include <type_traits>
 #include <boost/math/tools/is_standalone.hpp>
 
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 #ifndef BOOST_MATH_STANDALONE
 #include <boost/core/demangle.hpp>
 #endif

include/boost/math/tools/condition_numbers.hpp

@@ -9,6 +9,14 @@
 #include <limits>
 #include <boost/math/differentiation/finite_difference.hpp>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 namespace boost::math::tools {
 
 template<class Real, bool kahan=true>

include/boost/math/tools/engel_expansion.hpp

@@ -14,6 +14,14 @@
 #include <limits>
 #include <stdexcept>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 namespace boost::math::tools {
 
 template<typename Real, typename Z = int64_t>

include/boost/math/tools/luroth_expansion.hpp

@@ -13,6 +13,14 @@
 #include <limits>
 #include <stdexcept>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 namespace boost::math::tools {
 
 template<typename Real, typename Z = int64_t>

include/boost/math/tools/norms.hpp

@@ -12,6 +12,14 @@
 #include <boost/math/tools/assert.hpp>
 #include <boost/math/tools/complex.hpp>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 
 namespace boost::math::tools {
 

include/boost/math/tools/signal_statistics.hpp

@@ -14,6 +14,14 @@
 #include <boost/math/tools/header_deprecated.hpp>
 #include <boost/math/statistics/univariate_statistics.hpp>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 BOOST_MATH_HEADER_DEPRECATED("<boost/math/statistics/signal_statistics.hpp>");
 
 namespace boost::math::tools {

include/boost/math/tools/simple_continued_fraction.hpp

@@ -14,7 +14,14 @@
 #include <limits>
 #include <stdexcept>
 #include <sstream>
+
 #include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
 
 #ifndef BOOST_MATH_STANDALONE
 #include <boost/core/demangle.hpp>

include/boost/math/tools/univariate_statistics.hpp

@@ -12,6 +12,14 @@
 #include <boost/math/tools/assert.hpp>
 #include <boost/math/tools/header_deprecated.hpp>
 
+#include <boost/math/tools/is_standalone.hpp>
+#ifndef BOOST_MATH_STANDALONE
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
+#error "The header <boost/math/norms.hpp> can only be used in C++17 and later."
+#endif
+#endif
+
 BOOST_MATH_HEADER_DEPRECATED("<boost/math/statistics/univariate_statistics.hpp>");
 
 namespace boost::math::tools {