Use transparent functor for less<> and greater<>.

clang-tidy modernize-use-transparent-functors check.

BaseLib/ConfigTree.cpp

@@ -18,7 +18,7 @@
 // Explicitly instantiate the boost::property_tree::ptree which is a typedef to
 // the following basic_ptree.
 template class boost::property_tree::basic_ptree<std::string, std::string,
-                                                 std::less<std::string>>;
+                                                 std::less<>>;
 
 //! Collects swallowed error messages raised by the check during destruction of
 //! ConfigTree instances.

BaseLib/ConfigTree.h

@@ -20,8 +20,7 @@
 #include <boost/property_tree/ptree.hpp>
 
 extern template class boost::property_tree::basic_ptree<
-    std::string, std::string, std::less<std::string>>;
-
+    std::string, std::string, std::less<>>;
 
 namespace BaseLib
 {

NumLib/TimeStepping/Algorithms/CreateEvolutionaryPIDcontroller.cpp

@@ -49,7 +49,7 @@ std::unique_ptr<TimeStepAlgorithm> createEvolutionaryPIDcontroller(
     if (!fixed_output_times.empty())
     {
         // Remove possible duplicated elements and sort in descending order.
-        BaseLib::makeVectorUnique(fixed_output_times, std::greater<double>());
+        BaseLib::makeVectorUnique(fixed_output_times, std::greater<>());
     }
 
     //! \ogs_file_param{prj__time_loop__processes__process__time_stepping__EvolutionaryPIDcontroller__tol}

ProcessLib/Output/CreateOutput.cpp

@@ -124,7 +124,7 @@ std::unique_ptr<Output> createOutput(
     {
         fixed_output_times = std::move(*fixed_output_times_ptr);
         // Remove possible duplicated elements and sort in descending order.
-        BaseLib::makeVectorUnique(fixed_output_times, std::greater<double>());
+        BaseLib::makeVectorUnique(fixed_output_times, std::greater<>());
     }
 
     bool const output_iteration_results =