fix compiler errors

Signed-off-by: Eduard Fried <eduard.fried@soptim.de>

Author: frie-soptim

power_grid_model_c/power_grid_model/include/power_grid_model/common/exception.hpp

@@ -9,7 +9,6 @@
 
 #include <exception>
 #include <format>
-#include <numeric>
 #include <sstream>
 #include <string>
 #include <utility>
@@ -181,14 +180,9 @@ class UnsupportedRegulatorCombinationError : public PowerGridError {
 
 class ConflictingVoltageRegulatorURef : public PowerGridError {
   public:
-    ConflictingVoltageRegulatorURef(std::vector<ID> const& regulator_ids)
+    ConflictingVoltageRegulatorURef(std::string const& regulator_ids)
         : PowerGridError{
-              std::format("Conflicting u_ref values detected for voltage regulators {}.",
-                std::accumulate(std::next(regulator_ids.begin()), regulator_ids.end(),
-                  std::to_string(regulator_ids[0]),
-                  [](std::string a, ID b) { return a + ", " + std::to_string(b); }
-                )
-              )} {}
+              std::format("Conflicting u_ref values detected for voltage regulators {}.", regulator_ids)} {}
 };
 
 class AutomaticTapCalculationError : public PowerGridError {

power_grid_model_c/power_grid_model/include/power_grid_model/main_model_impl.hpp

@@ -554,7 +554,15 @@ class MainModelImpl {
                 }
             }
             if (!conflicting_regulators.empty()) {
-                throw ConflictingVoltageRegulatorURef{conflicting_regulators};
+                // join IDs like this, because of various compiler errors with std::format and
+                // std::accumulate when used in exception constructor
+                std::ostringstream oss;
+                for (size_t i = 0; i < conflicting_regulators.size(); ++i) {
+                    if (i > 0) oss << ", ";
+                    oss << conflicting_regulators[i];
+                }
+                std::string ids = oss.str();
+                throw ConflictingVoltageRegulatorURef{ids};
             }
         }
     }