From: Matthias Maier <tamiko@43-1.org>
Date: Fri, 6 Sep 2019 00:18:13 +0000 (-0500)
Subject: Add a static_assert
X-Git-Tag: v9.2.0-rc1~1136^2~1
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=89ca962317ad845c3ffe126554c710f1962c75de;p=dealii.git

Add a static_assert
---

diff --git a/include/deal.II/base/utilities.h b/include/deal.II/base/utilities.h
index 4c9ae69d84..bdf6a13ee3 100644
--- a/include/deal.II/base/utilities.h
+++ b/include/deal.II/base/utilities.h
@@ -1032,13 +1032,18 @@ namespace Utilities
   inline T
   fixed_power(const T x)
   {
+    static_assert(
+      !std::is_integral<T>::value || (N >= 0),
+      "The non-type template parameter N must be a non-negative integer for integral type T");
+
     if (N == 0)
       return T(1.);
     else if (N < 0)
       return T(1.) / fixed_power<-N>(x);
     else
       // Use exponentiation by squaring:
-      return ((N % 2 == 1) ? x * fixed_power<N / 2>(x * x) : fixed_power<N / 2>(x * x));
+      return ((N % 2 == 1) ? x * fixed_power<N / 2>(x * x) :
+                             fixed_power<N / 2>(x * x));
   }