use std::apply instead of Dune backport

amdis/operations/Composer.impl.hpp

 #pragma once
 
+#include <tuple>
 #include <utility>
-#include <amdis/operations/Composer.hpp>
 
 #include <amdis/operations/Arithmetic.hpp>
+#include <amdis/operations/Composer.hpp>
 
 namespace AMDiS { namespace Operation {
 
@@ -17,7 +18,7 @@ namespace AMDiS { namespace Operation {
     // d_i(f)[g...] * d_j(g_i)
     auto term_i = [&](auto const _i)
     {
-      auto di_f = Dune::Std::apply([&](auto const&... gs) {
+      auto di_f = std::apply([&](auto const&... gs) {
         return compose(partial(c.f_, _i), gs...);
       }, c.gs_);
 
@@ -26,7 +27,7 @@ namespace AMDiS { namespace Operation {
     };
 
     // sum_i [ d_i(f)[g...] * d_j(g_i) ]
-    return Dune::Std::apply([&](auto const... _i)
+    return std::apply([&](auto const... _i)
     {
       return compose(Plus{}, term_i(_i)...);
     }, index_seq);