From de1f331ebc93ccf3880c9684e3ba577f87b8b363 Mon Sep 17 00:00:00 2001
From: Matt Borland <matt.borland1@gmail.com>
Date: Sat, 26 Sep 2020 22:18:54 -0500
Subject: [PATCH] prime approximation function for a range

---
 include/boost/math/special_functions/prime_sieve.hpp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/boost/math/special_functions/prime_sieve.hpp b/include/boost/math/special_functions/prime_sieve.hpp
index cf6a39dc9..e63adfc21 100644
--- a/include/boost/math/special_functions/prime_sieve.hpp
+++ b/include/boost/math/special_functions/prime_sieve.hpp
@@ -235,12 +235,18 @@ void sequential_segmented_sieve(Integer lower_bound, Integer upper_bound, Contai
 } // End namespace detail
 
 template<class Integer>
-constexpr Integer prime_approximation(Integer upper_bound)
+constexpr Integer prime_approximation(const Integer upper_bound)
 {
     constexpr auto c = 30 * std::log(113) / 113; // Magic numbers from wikipedia
     return static_cast<Integer>(std::floor(c * upper_bound / std::log(static_cast<double>(upper_bound))));
 }
 
+template<class Integer>
+constexpr Integer prime_approximation(const Integer lower_bound, const Integer upper_bound)
+{
+    return prime_approximation(upper_bound) - prime_approximation(lower_bound);
+}
+
 template<class Integer>
 constexpr void prime_reserve(Integer upper_bound, std::vector<Integer> &prime_container)
 {