From: Daniel Arndt <daniel.arndt@iwr.uni-heidelberg.de>
Date: Fri, 24 Aug 2018 09:29:03 +0000 (+0200)
Subject: Assert positive exponents in Utilities::pow
X-Git-Tag: v9.1.0-rc1~772^2~1
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=31d6094e306bc58a7ec1e8017c40c45c82645bc4;p=dealii.git

Assert positive exponents in Utilities::pow
---

diff --git a/include/deal.II/base/utilities.h b/include/deal.II/base/utilities.h
index bcb1e8a33f..e469558f59 100644
--- a/include/deal.II/base/utilities.h
+++ b/include/deal.II/base/utilities.h
@@ -347,12 +347,18 @@ namespace Utilities
 
   /**
    * A replacement for <code>std::pow</code> that allows compile-time
-   * calculations for constant expression arguments.
+   * calculations for constant expression arguments. The exponent @p iexp
+   * must not be negative.
    */
   constexpr unsigned int
-  pow(const unsigned int base, const unsigned int iexp)
+  pow(const unsigned int base, const int iexp)
   {
-    return iexp == 0 ? 1 : base * dealii::Utilities::pow(base, iexp - 1);
+#ifdef DEAL_II_WITH_CXX17
+    AssertThrow(iexp >= 0, ExcMessage("The exponent must not be negative!"));
+#endif
+    return iexp <= 0 ? 1 :
+                       (((iexp % 2 == 1) ? base : 1) *
+                        dealii::Utilities::pow(base * base, iexp / 2));
   }
 
   /**