Update RegisterManager's constructor.

src/qx/RegisterManager.cpp

@@ -18,8 +18,9 @@ struct RegisterManagerError : public SimulationError {
 };
 
 RegisterManager::RegisterManager(const V3OneProgram &program) {
-    auto &&qubit_variable_sizes = program->variables.get_vec()
-        | ranges::views::filter([&](const V3OneVariable &variable) { return is_qubit_variable(*variable); })
+    auto &&qubit_variables = program->variables.get_vec()
+        | ranges::views::filter([&](const V3OneVariable &variable) { return is_qubit_variable(*variable); });
+    auto &&qubit_variable_sizes = qubit_variables
         | ranges::views::transform([](const V3OneVariable &variable) { return v3_types::size_of(variable->typ); });
     qubit_register_size_ = ranges::accumulate(qubit_variable_sizes, size_t{});
 
@@ -31,10 +32,7 @@ RegisterManager::RegisterManager(const V3OneProgram &program) {
     qubit_index_to_variable_name_.resize(qubit_register_size_);
 
     auto current_qubit_index = size_t{};
-    for (const auto &variable: program->variables) {
-        if (!is_qubit_variable(*variable)) {
-            continue;
-        }
+    for (auto &&variable: qubit_variables) {
         const auto &variable_size = static_cast<size_t>(cqasm::v3x::types::size_of(variable->typ));
         variable_name_to_qubit_range_[variable->name] = QubitRange{ current_qubit_index, variable_size };
         std::fill(qubit_index_to_variable_name_.begin() + static_cast<long>(current_qubit_index),