Properly deprecate power.hh.

CHANGELOG.md

@@ -48,6 +48,9 @@
   and will be removed after Dune 2.9. Use `Communication` respectively
   `getCommunication` instead.
 
+- The header `power.hh` is deprecated. Use `Dune::power` from
+  `math.hh` instead.
+
 # Release 2.8
 
 - Set minimal required CMake version in cmake to >= 3.13.

dune/common/power.hh

@@ -3,6 +3,8 @@
 #ifndef DUNE_COMMON_POWER_HH
 #define DUNE_COMMON_POWER_HH
 
+#warning The header power.hh is deprecated. Use power from math.hh instead.
+
 /** \file
     \brief Various implementations of the power function for run-time and static arguments
  */

dune/common/test/powertest.cc

@@ -5,6 +5,7 @@
 
 #include <iostream>
 
+#include <dune/common/deprecated.hh>
 #include <dune/common/exceptions.hh>
 #include <dune/common/math.hh>
 #include <dune/common/power.hh>
@@ -40,6 +41,7 @@ int main (int argc, char** argv) try
   enum { dummy = power(2,2) };
 
   // Test legacy power implementation
+  DUNE_NO_DEPRECATED_BEGIN
   if (Power<0>::eval(4) != 1)
     DUNE_THROW(MathError, "Power implementation does not compute the correct result");
 
@@ -52,6 +54,7 @@ int main (int argc, char** argv) try
   if (Power<3>::eval(4) != 64)
     DUNE_THROW(MathError, "Power implementation does not compute the correct result");
 
+  DUNE_NO_DEPRECATED_END
   return 0;
 }
 catch (Exception& e)