Begin symbol table performance improvement

src/language/PugsParser.cpp

@@ -783,23 +783,10 @@ class SymbolTable
   };
 
  private:
-  std::unordered_map<std::string, Attributes> m_symbol_list;
+  std::vector<std::pair<std::string, Attributes>> m_symbol_list;
   std::shared_ptr<SymbolTable> m_parent_table;
 
  public:
-  void
-  removeUnmatchedSymbols(const SymbolTable& given_table)
-  {
-    Assert(m_parent_table == given_table.m_parent_table);
-    for (decltype(m_symbol_list)::iterator i_symbol = m_symbol_list.begin(); i_symbol != m_symbol_list.end();) {
-      if (given_table.m_symbol_list.find(i_symbol->first) == given_table.m_symbol_list.end()) {
-        i_symbol = m_symbol_list.erase(i_symbol);
-      } else {
-        ++i_symbol;
-      }
-    }
-  }
-
   friend std::ostream&
   operator<<(std::ostream& os, const SymbolTable& symbol_table)
   {
@@ -814,7 +801,15 @@ class SymbolTable
   auto
   find(const std::string& symbol)
   {
-    auto i_symbol = m_symbol_list.find(symbol);
+    auto i_symbol = m_symbol_list.end();
+
+    for (auto i_stored_symbol = m_symbol_list.begin(); i_stored_symbol != m_symbol_list.end(); ++i_stored_symbol) {
+      if (i_stored_symbol->first == symbol) {
+        i_symbol = i_stored_symbol;
+        break;
+      }
+    }
+
     if (i_symbol != m_symbol_list.end()) {
       return std::make_pair(i_symbol, true);
     } else {
@@ -829,7 +824,12 @@ class SymbolTable
   auto
   add(const std::string& symbol)
   {
-    return m_symbol_list.insert(std::make_pair(symbol, Attributes{}));
+    for (auto i_stored_symbol = m_symbol_list.begin(); i_stored_symbol != m_symbol_list.end(); ++i_stored_symbol) {
+      if (i_stored_symbol->first == symbol) {
+        return std::make_pair(i_stored_symbol, false);
+      }
+    }
+    return std::make_pair(m_symbol_list.emplace(m_symbol_list.end(), std::make_pair(symbol, Attributes())), true);
   }
 
   SymbolTable(const std::shared_ptr<SymbolTable>& parent_table = nullptr) : m_parent_table(parent_table)
@@ -1688,7 +1688,6 @@ execute_node(Node& n, std::shared_ptr<SymbolTable>& symbol_table, ExecPolicyT& e
         }
       }
 
-      bloc_symbol_table->removeUnmatchedSymbols(context_symbol_table);
       execute_node(*n.children[2], bloc_symbol_table, exec_policy);
     }
     break;