diff --git a/scripts/loc.py b/scripts/loc.py
index d121863d..97e0ac5c 100644
--- a/scripts/loc.py
+++ b/scripts/loc.py
@@ -8,12 +8,16 @@ def get_loc(path):
 
 def get_loc_for_dir(path):
     loc = 0
+    loc_ex = 0
     for root, dirs, files in os.walk(path):
         for file in files:
             if file.endswith('.h'):
                 _i = get_loc(os.path.join(root, file))
                 print(f"{file}: {_i}")
-                loc += _i
-    return loc
+                if file.startswith('_'):
+                    loc_ex += _i
+                else:
+                    loc += _i
+    return f'{loc} (+{loc_ex})'
 
 print(get_loc_for_dir('src'))
\ No newline at end of file
diff --git a/src/compiler.h b/src/compiler.h
index b0ad3782..8ff028cd 100644
--- a/src/compiler.h
+++ b/src/compiler.h
@@ -884,8 +884,7 @@ __LISTCOMP:
             consume(TK("@id"));
             int dummy_t = co()->add_name(parser->prev.str(), NAME_SPECIAL);
             if(match(TK("("))){
-                EXPR();
-                consume(TK(")"));
+                EXPR(); consume(TK(")"));
             }else{
                 emit(OP_LOAD_NONE);
             }
@@ -1077,7 +1076,11 @@ __LISTCOMP:
         return parser->src->snapshot(lineno, cursor);
     }
 
-    void syntaxError(_Str msg){ throw CompileError("SyntaxError", msg, getLineSnapshot()); }
-    void indentationError(_Str msg){ throw CompileError("IndentationError", msg, getLineSnapshot()); }
-    void unexpectedError(_Str msg){ throw CompileError("UnexpectedError", msg, getLineSnapshot()); }
+    void __throw_e(_Str type, _Str msg){
+        auto e = _Error0("SyntaxError", msg, false);
+        e.st_push(getLineSnapshot());
+        throw e;
+    }
+    void syntaxError(_Str msg){ __throw_e("SyntaxError", msg); }
+    void indentationError(_Str msg){ __throw_e("IndentationError", msg); }
 };
\ No newline at end of file
diff --git a/src/error.h b/src/error.h
index 9c0ce0bc..a4b85d92 100644
--- a/src/error.h
+++ b/src/error.h
@@ -52,12 +52,10 @@ struct SourceMetadata {
             removedSpaces = pair.second - pair.first - line.size();
             if(line.empty()) line = "<?>";
         }
-        ss << "    " << line << '\n';
+        ss << "    " << line;
         if(cursor && line != "<?>" && cursor >= pair.first && cursor <= pair.second){
             auto column = cursor - pair.first - removedSpaces;
-            if(column >= 0){
-                ss << "    " << std::string(column, ' ') << "^\n";
-            }
+            if(column >= 0) ss << "\n    " << std::string(column, ' ') << "^";
         }
         return ss.str();
     }
@@ -69,37 +67,24 @@ struct SourceMetadata {
 
 typedef pkpy::shared_ptr<SourceMetadata> _Source;
 
-class _Error : public std::exception {
-private:
-    _Str _what;
+class _Error0 : public std::exception {
+    _Str type;
+    _Str msg;
+    bool is_runtime_error;
+    std::stack<_Str> stacktrace;
+
+    mutable _Str _what_cached;
 public:
-    _Error(_Str type, _Str msg, _Str desc){
-        _what = desc + type + ": " + msg;
-    }
+    _Error0(_Str type, _Str msg, bool is_runtime_error): type(type), msg(msg), is_runtime_error(is_runtime_error) {}
+    void st_push(_Str snapshot){ stacktrace.push(snapshot); }
 
     const char* what() const noexcept override {
-        return _what.c_str();
-    }
-};
-
-class CompileError : public _Error {
-public:
-    CompileError(_Str type, _Str msg, _Str snapshot)
-        : _Error(type, msg, snapshot) {}
-};
-
-class RuntimeError : public _Error {
-private:
-    static _Str __concat(std::stack<_Str> snapshots){
+        std::stack<_Str> st(stacktrace);
         _StrStream ss;
-        ss << "Traceback (most recent call last):" << '\n';
-        while(!snapshots.empty()){
-            ss << snapshots.top();
-            snapshots.pop();
-        }
-        return ss.str();
+        if(is_runtime_error) ss << "Traceback (most recent call last):\n";
+        while(!st.empty()) { ss << st.top() << '\n'; st.pop(); }
+        ss << type << ": " << msg;
+        _what_cached = ss.str();
+        return _what_cached.c_str();
     }
-public:
-    RuntimeError(_Str type, _Str msg, const std::stack<_Str>& snapshots)
-        : _Error(type, msg, __concat(snapshots)) {}
 };
\ No newline at end of file
diff --git a/src/pocketpy.h b/src/pocketpy.h
index 115d54b9..0dd7514b 100644
--- a/src/pocketpy.h
+++ b/src/pocketpy.h
@@ -8,10 +8,11 @@ _Code VM::compile(_Str source, _Str filename, CompileMode mode) {
     Compiler compiler(this, source.c_str(), filename, mode);
     try{
         return compiler.__fillCode();
-    }catch(_Error& e){
+    }catch(_Error0& e){
         throw e;
     }catch(std::exception& e){
-        throw CompileError("UnexpectedError", e.what(), compiler.getLineSnapshot());
+        compiler.__throw_e("UnexpectedError", e.what());
+        return nullptr;
     }
 }
 
diff --git a/src/vm.h b/src/vm.h
index 50812dea..6dcf484e 100644
--- a/src/vm.h
+++ b/src/vm.h
@@ -520,13 +520,17 @@ public:
         if(_module == nullptr) _module = _main;
         try {
             _Code code = compile(source, filename, mode);
-            //if(filename != "<builtins>") std::cout << disassemble(code) << std::endl;
             return _exec(code, _module, pkpy::make_shared<PyVarDict>());
-        }catch (const _Error& e){
+        }catch (const _Error0& e){
             *_stderr << e.what() << '\n';
         }
         catch (const std::exception& e) {
-            auto re = RuntimeError("UnexpectedError", e.what(), _cleanErrorAndGetSnapshots());
+            auto re = _Error0("UnexpectedError", e.what(), false);
+            auto snapshots = _cleanErrorAndGetSnapshots();
+            while(!snapshots.empty()){
+                re.st_push(snapshots.top());
+                snapshots.pop();
+            }
             *_stderr << re.what() << '\n';
         }
         return nullptr;
@@ -535,7 +539,7 @@ public:
     template<typename ...Args>
     Frame* __push_new_frame(Args&&... args){
         if(callstack.size() > maxRecursionDepth){
-            throw RuntimeError("RecursionError", "maximum recursion depth exceeded", _cleanErrorAndGetSnapshots());
+            _error("RecursionError", "maximum recursion depth exceeded");
         }
         callstack.emplace_back(std::make_unique<Frame>(std::forward<Args>(args)...));
         return callstack.back().get();
@@ -888,7 +892,13 @@ public:
     /***** Error Reporter *****/
 private:
     void _error(const _Str& name, const _Str& msg){
-        throw RuntimeError(name, msg, _cleanErrorAndGetSnapshots());
+        auto e = _Error0(name, msg, true);
+        std::stack<_Str> snapshots = _cleanErrorAndGetSnapshots();
+        while (!snapshots.empty()){
+            e.st_push(snapshots.top());
+            snapshots.pop();
+        }
+        throw e;
     }
 
     std::stack<_Str> _cleanErrorAndGetSnapshots(){