From 56293860d136db6d38b1e7a1d2e358d429ed1d75 Mon Sep 17 00:00:00 2001
From: Andrew Johnson <andrew.johnson@arjohnsonau.com>
Date: Fri, 1 Aug 2025 15:45:15 +0800
Subject: [PATCH 1/2] Avoid using long double in fourier integrals when not
 supported

---
 .../detail/ooura_fourier_integrals_detail.hpp    | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/include/boost/math/quadrature/detail/ooura_fourier_integrals_detail.hpp b/include/boost/math/quadrature/detail/ooura_fourier_integrals_detail.hpp
index 49677a8d2..094d84760 100644
--- a/include/boost/math/quadrature/detail/ooura_fourier_integrals_detail.hpp
+++ b/include/boost/math/quadrature/detail/ooura_fourier_integrals_detail.hpp
@@ -199,7 +199,11 @@ public:
                 add_level<double>(i);
             }
             else if (std::is_same<Real, double>::value) {
+#ifndef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
                 add_level<long double>(i);
+#else
+                add_level<double>(i);
+#endif
             }
             else {
                 add_level<Real>(i);
@@ -270,7 +274,11 @@ public:
                 add_level<double>(ii);
             }
             else if (std::is_same<Real, double>::value) {
+#ifndef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
                 add_level<long double>(ii);
+#else
+                add_level<double>(ii);
+#endif
             }
             else {
                 add_level<Real>(ii);
@@ -468,7 +476,11 @@ public:
                 add_level<double>(i);
             }
             else if (std::is_same<Real, double>::value) {
+#ifndef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
                 add_level<long double>(i);
+#else
+                add_level<double>(i);
+#endif
             }
             else {
                 add_level<Real>(i);
@@ -516,7 +528,11 @@ public:
                 add_level<double>(ii);
             }
             else if (std::is_same<Real, double>::value) {
+#ifndef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
                 add_level<long double>(ii);
+#else
+                add_level<double>(ii);
+#endif
             }
             else {
                 add_level<Real>(ii);

From 31b94bfc38031e8bd797938759edb1ae2cedf963 Mon Sep 17 00:00:00 2001
From: Matt Borland <matt@mattborland.com>
Date: Fri, 1 Aug 2025 12:40:52 -0400
Subject: [PATCH 2/2] Use `if constexpr` for type based branching in fourier
 integrals

---
 .../detail/ooura_fourier_integrals_detail.hpp    | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/include/boost/math/quadrature/detail/ooura_fourier_integrals_detail.hpp b/include/boost/math/quadrature/detail/ooura_fourier_integrals_detail.hpp
index 094d84760..c677852da 100644
--- a/include/boost/math/quadrature/detail/ooura_fourier_integrals_detail.hpp
+++ b/include/boost/math/quadrature/detail/ooura_fourier_integrals_detail.hpp
@@ -195,10 +195,10 @@ public:
         lweights_.reserve(levels);
 
         for (size_t i = 0; i < levels; ++i) {
-            if (std::is_same<Real, float>::value) {
+            BOOST_MATH_IF_CONSTEXPR (std::is_same<Real, float>::value) {
                 add_level<double>(i);
             }
-            else if (std::is_same<Real, double>::value) {
+            else BOOST_MATH_IF_CONSTEXPR (std::is_same<Real, double>::value) {
 #ifndef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
                 add_level<long double>(i);
 #else
@@ -270,10 +270,10 @@ public:
         size_t max_additional_levels = 4;
         while (big_nodes_.size() < requested_levels_ + max_additional_levels) {
             size_t ii = big_nodes_.size();
-            if (std::is_same<Real, float>::value) {
+            BOOST_MATH_IF_CONSTEXPR (std::is_same<Real, float>::value) {
                 add_level<double>(ii);
             }
-            else if (std::is_same<Real, double>::value) {
+            else BOOST_MATH_IF_CONSTEXPR (std::is_same<Real, double>::value) {
 #ifndef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
                 add_level<long double>(ii);
 #else
@@ -472,10 +472,10 @@ public:
         lweights_.reserve(levels);
 
         for (size_t i = 0; i < levels; ++i) {
-            if (std::is_same<Real, float>::value) {
+            BOOST_MATH_IF_CONSTEXPR (std::is_same<Real, float>::value) {
                 add_level<double>(i);
             }
-            else if (std::is_same<Real, double>::value) {
+            else BOOST_MATH_IF_CONSTEXPR (std::is_same<Real, double>::value) {
 #ifndef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
                 add_level<long double>(i);
 #else
@@ -524,10 +524,10 @@ public:
         size_t max_additional_levels = 4;
         while (big_nodes_.size() < requested_levels_ + max_additional_levels) {
             size_t ii = big_nodes_.size();
-            if (std::is_same<Real, float>::value) {
+            BOOST_MATH_IF_CONSTEXPR (std::is_same<Real, float>::value) {
                 add_level<double>(ii);
             }
-            else if (std::is_same<Real, double>::value) {
+            else BOOST_MATH_IF_CONSTEXPR (std::is_same<Real, double>::value) {
 #ifndef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
                 add_level<long double>(ii);
 #else