Using visitors instead of for-each

config.diff

diff --git a/llarp/config/definition.cpp b/llarp/config/definition.cpp
index 5e45dee6..f6f8800a 100644
--- a/llarp/config/definition.cpp
+++ b/llarp/config/definition.cpp
@@ -60,17 +60,27 @@ Configuration::lookupDefinitionOrThrow(string_view section, string_view name)
       const_cast<const Configuration*>(this)->lookupDefinitionOrThrow(section, name));
 }
 
+using SectionVisitor = std::function<void(const std::string&, const DefinitionMap&)>;
+const auto visitSections = [](const SectionMap& sections, SectionVisitor visitor) {
+  for (const auto& pair : sections)
+  {
+    visitor(pair.first, pair.second);
+  }
+};
+
+using DefVisitor = std::function<void(const std::string&, const ConfigDefinition_ptr&)>;
+const auto visitDefinitions = [](const DefinitionMap& defs, DefVisitor visitor) {
+  for (const auto& pair : defs)
+  {
+    visitor(pair.first, pair.second);
+  }
+};
+
 void
 Configuration::validate()
 {
-  for (const auto& pair : m_definitions)
-  {
-    const std::string& section = pair.first;
-
-    const auto& sectionDefinitions = pair.second;
-    for (const auto& defPair : sectionDefinitions)
-    {
-      const auto& def = defPair.second;
+  visitSections(m_definitions, [&](const std::string& section, const DefinitionMap& defs) {
+    visitDefinitions(defs, [&](const std::string&, const ConfigDefinition_ptr& def) {
       if (def->required and def->numFound < 1)
       {
         throw std::invalid_argument(stringify(
@@ -79,8 +89,8 @@ Configuration::validate()
 
       // should be handled earlier in ConfigDefinition::parseValue()
       assert(def->numFound == 1 or def->multiValued);
-    }
-  }
+    });
+  });
 }
 
 std::string