use vector space operation in NewtonIteration

amdis/nonlin/NewtonIteration.inc.hpp

@@ -28,8 +28,7 @@ Flag NewtonIteration<Problem>::oneIteration(AdaptInfo& adaptInfo, Flag toDo)
   prob_->solver()->apply(stepSolution_->impl(), prob_->rhsVector()->impl(), stat);
 
   // u = u + d
-  Recursive::transform(prob_->solutionVector()->impl(),
-    Operation::Plus{}, prob_->solutionVector()->impl(), stepSolution_->impl());
+  prob_->solutionVector() += stepSolution_;
 
   // L2-norm
   err_ = integrate(sqr(this->stepSolution()), prob_->gridView());