From 60286202fdf085c5037d058bbc938e39bd3cb369 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Thu, 12 May 2016 17:32:41 +1000
Subject: [PATCH] maths: make stirling inline rather than constexpr

stirling uses cmath functions which aren't constexpr, such as std::pow.
this sometimes works under linux/gcc but fails under clang/freebsd
---
 maths.hpp | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/maths.hpp b/maths.hpp
index ec4750e5..74196267 100644
--- a/maths.hpp
+++ b/maths.hpp
@@ -399,11 +399,13 @@ namespace util {
 
     //-----------------------------------------------------------------------------
     /// stirlings approximation of factorials
-    constexpr uintmax_t
+    inline uintmax_t
     stirling  (unsigned n)
     {
+        using real_t = double;
+
         return static_cast<uintmax_t> (
-            std::sqrt (2 * PI<float> * n) * std::pow (n / E<float>, n)
+            std::sqrt (2 * PI<real_t> * n) * std::pow (n / E<real_t>, n)
         );
     }