diff --git a/src/nasal_dbg.h b/src/nasal_dbg.h
index 2aa1b0c..0fd2b93 100644
--- a/src/nasal_dbg.h
+++ b/src/nasal_dbg.h
@@ -163,13 +163,11 @@ public:
         next(true), fsize(0),
         break_file_index(0), break_line(0),
         do_operand_count(false) {}
-    void run(
-        const codegen&,
-        const linker&,
-        const std::vector<std::string>&,
-        bool,
-        bool
-    );
+    void run(const codegen&,
+             const linker&,
+             const std::vector<std::string>&,
+             bool,
+             bool);
 };
 
 }
diff --git a/src/nasal_err.cpp b/src/nasal_err.cpp
index 42a71d3..c57aa20 100644
--- a/src/nasal_err.cpp
+++ b/src/nasal_err.cpp
@@ -120,8 +120,9 @@ void error::warn(const std::string& stage, const std::string& info) {
     std::clog << orange << stage << ": " << white << info << reset << "\n\n";
 }
 
-void error::err(
-    const std::string& stage, const span& loc, const std::string& info) {
+void error::err(const std::string& stage,
+                const span& loc,
+                const std::string& info) {
     // load error occurred file into string lines
     load(loc.file);
 
diff --git a/src/nasal_import.cpp b/src/nasal_import.cpp
index 9d94777..b5273e5 100644
--- a/src/nasal_import.cpp
+++ b/src/nasal_import.cpp
@@ -41,8 +41,8 @@ std::string linker::get_path(expr* node) {
     return content->get_content();
 }
 
-std::string linker::find_real_file_path(
-    const std::string& filename, const span& location) {
+std::string linker::find_real_file_path(const std::string& filename,
+                                        const span& location) {
     // first add file name itself into the file path
     std::vector<fs::path> path_list = {filename};
 
diff --git a/src/nasal_parse.cpp b/src/nasal_parse.cpp
index dc3b1a2..c0f3f98 100644
--- a/src/nasal_parse.cpp
+++ b/src/nasal_parse.cpp
@@ -254,11 +254,11 @@ vector_expr* parse::vec() {
     // panic set for this token is not ','
     // this is the FIRST set of calculation
     // array end with tok::null=0
-    const tok panic[]={
-        tok::id,tok::str,tok::num,tok::tktrue,
-        tok::tkfalse,tok::opnot,tok::sub,tok::tknil,
-        tok::func,tok::var,tok::lcurve,tok::floater,
-        tok::lbrace,tok::lbracket,tok::null
+    const tok panic[] = {
+        tok::id, tok::str, tok::num, tok::tktrue,
+        tok::tkfalse, tok::opnot, tok::sub, tok::tknil,
+        tok::func, tok::var, tok::lcurve, tok::floater,
+        tok::lbrace, tok::lbracket, tok::null
     };
     auto node = new vector_expr(toks[ptr].loc);
     match(tok::lbracket);
@@ -713,11 +713,11 @@ call_vector* parse::callv() {
     // panic set for this token is not ','
     // this is the FIRST set of subvec
     // array end with tok::null=0
-    const tok panic[]={
-        tok::id,tok::str,tok::num,tok::tktrue,
-        tok::tkfalse,tok::opnot,tok::sub,tok::tknil,
-        tok::func,tok::var,tok::lcurve,tok::floater,
-        tok::lbrace,tok::lbracket,tok::colon,tok::null
+    const tok panic[] = {
+        tok::id, tok::str, tok::num, tok::tktrue,
+        tok::tkfalse, tok::opnot, tok::sub, tok::tknil,
+        tok::func, tok::var, tok::lcurve, tok::floater,
+        tok::lbrace, tok::lbracket, tok::colon, tok::null
     };
     auto node = new call_vector(toks[ptr].loc);
     match(tok::lbracket);
@@ -743,11 +743,11 @@ call_function* parse::callf() {
     // panic set for this token is not ','
     // this is the FIRST set of calculation/hashmember
     // array end with tok::null=0
-    const tok panic[]={
-        tok::id,tok::str,tok::num,tok::tktrue,
-        tok::tkfalse,tok::opnot,tok::sub,tok::tknil,
-        tok::func,tok::var,tok::lcurve,tok::floater,
-        tok::lbrace,tok::lbracket,tok::null
+    const tok panic[] = {
+        tok::id, tok::str,tok::num, tok::tktrue,
+        tok::tkfalse, tok::opnot, tok::sub, tok::tknil,
+        tok::func, tok::var, tok::lcurve, tok::floater,
+        tok::lbrace, tok::lbracket, tok::null
     };
     auto node = new call_function(toks[ptr].loc);
     bool special_call=check_special_call();
@@ -802,7 +802,7 @@ expr* parse::definition() {
 }
 
 multi_identifier* parse::incurve_def() {
-    const auto& loc=toks[ptr].loc;
+    const auto& loc = toks[ptr].loc;
     match(tok::lcurve);
     match(tok::var);
     auto node = multi_id();
@@ -813,7 +813,7 @@ multi_identifier* parse::incurve_def() {
 }
 
 multi_identifier* parse::outcurve_def() {
-    const auto& loc=toks[ptr].loc;
+    const auto& loc = toks[ptr].loc;
     match(tok::lcurve);
     auto node = multi_id();
     update_location(node);
@@ -840,12 +840,13 @@ multi_identifier* parse::multi_id() {
 }
 
 tuple_expr* parse::multi_scalar() {
-    // if check_call_memory is true,we will check if value called here can reach a memory space
-    const tok panic[]={
-        tok::id,tok::str,tok::num,tok::tktrue,
-        tok::tkfalse,tok::opnot,tok::sub,tok::tknil,
-        tok::func,tok::var,tok::lcurve,tok::floater,
-        tok::lbrace,tok::lbracket,tok::null
+    // if check_call_memory is true,
+    // we will check if value called here can reach a memory space
+    const tok panic[] = {
+        tok::id, tok::str,tok::num, tok::tktrue,
+        tok::tkfalse, tok::opnot, tok::sub, tok::tknil,
+        tok::func, tok::var, tok::lcurve, tok::floater,
+        tok::lbrace, tok::lbracket, tok::null
     };
     auto node = new tuple_expr(toks[ptr].loc);
     match(tok::lcurve);
diff --git a/src/nasal_type.cpp b/src/nasal_type.cpp
index 537db2f..70324f7 100644
--- a/src/nasal_type.cpp
+++ b/src/nasal_type.cpp
@@ -98,6 +98,30 @@ std::ostream& operator<<(std::ostream& out, nas_hash& hash) {
     return out;
 }
 
+std::ostream& operator<<(std::ostream& out, nas_func& func) {
+    out << "func(";
+    
+    std::vector<std::string> argument_list = {};
+    argument_list.resize(func.keys.size());
+    for(const auto& key : func.keys) {
+        argument_list[key.second-1] = key.first;
+    }
+
+    for(const auto& key : argument_list) {
+        out << key;
+        if (key != argument_list.back()) {
+            out << ", ";
+        }
+    }
+    if (func.dynamic_parameter_index>=0) {
+        out << (argument_list.size()? ", ":"");
+        out << func.dynamic_parameter_name << "...";
+    }
+
+    out << ") {..}";
+    return out;
+}
+
 void nas_func::clear() {
     dynamic_parameter_index = -1;
     local.clear();
@@ -256,21 +280,24 @@ std::string var::to_str() {
         tmp.erase(tmp.find_last_not_of('.')+1, std::string::npos);
         return tmp;
     }
-    return "";
+
+    std::stringstream ss;
+    ss << *this;
+    return ss.str();
 }
 
 std::ostream& operator<<(std::ostream& out, var& ref) {
     switch(ref.type) {
-        case vm_type::vm_none:  out << "undefined";   break;
-        case vm_type::vm_nil:   out << "nil";         break;
-        case vm_type::vm_num:   out << ref.val.num;   break;
-        case vm_type::vm_str:   out << ref.str();     break;
-        case vm_type::vm_vec:   out << ref.vec();     break;
-        case vm_type::vm_hash:  out << ref.hash();    break;
-        case vm_type::vm_func:  out << "func(..) {..}"; break;
-        case vm_type::vm_ghost: out << ref.ghost();   break;
-        case vm_type::vm_co:    out << ref.co();      break;
-        case vm_type::vm_map:   out << ref.map();     break;
+        case vm_type::vm_none:  out << "undefined"; break;
+        case vm_type::vm_nil:   out << "nil";       break;
+        case vm_type::vm_num:   out << ref.val.num; break;
+        case vm_type::vm_str:   out << ref.str();   break;
+        case vm_type::vm_vec:   out << ref.vec();   break;
+        case vm_type::vm_hash:  out << ref.hash();  break;
+        case vm_type::vm_func:  out << ref.func();  break;
+        case vm_type::vm_ghost: out << ref.ghost(); break;
+        case vm_type::vm_co:    out << ref.co();    break;
+        case vm_type::vm_map:   out << ref.map();   break;
         default: break;
     }
     return out;
diff --git a/src/nasal_type.h b/src/nasal_type.h
index b802066..d7e3b9d 100644
--- a/src/nasal_type.h
+++ b/src/nasal_type.h
@@ -15,6 +15,7 @@ enum class vm_type: u8 {
     vm_ret,      // return addres(program counter) 
     vm_nil,      // nil
     vm_num,      // number
+
     /* gc object */
     vm_str,      // string
     vm_vec,      // vector
@@ -24,6 +25,7 @@ enum class vm_type: u8 {
     vm_ghost,    // ghost type
     vm_co,       // coroutine
     vm_map,      // for globals and namespaces
+
     /* mark type range */
     vm_type_size_max
 };
@@ -153,9 +155,13 @@ struct nas_func {
     // parameter table, u32 begins from 1
     std::unordered_map<std::string, u32> keys;
 
+    // dynamic parameter name
+    std::string dynamic_parameter_name;
+
     nas_func():
         dynamic_parameter_index(-1), entry(0),
-        parameter_size(0), local_size(0) {}
+        parameter_size(0), local_size(0),
+        dynamic_parameter_name("") {}
     void clear();
 };
 
@@ -277,6 +283,7 @@ struct nas_val {
 
 std::ostream& operator<<(std::ostream&, nas_vec&);
 std::ostream& operator<<(std::ostream&, nas_hash&);
+std::ostream& operator<<(std::ostream&, nas_func&);
 std::ostream& operator<<(std::ostream&, nas_map&);
 std::ostream& operator<<(std::ostream&, const nas_ghost&);
 std::ostream& operator<<(std::ostream&, const nas_co&);
diff --git a/src/nasal_vm.h b/src/nasal_vm.h
index 2286b01..d6daddb 100644
--- a/src/nasal_vm.h
+++ b/src/nasal_vm.h
@@ -311,6 +311,7 @@ inline void vm::o_deft() {
 
 inline void vm::o_dyn() {
     ctx.top[0].func().dynamic_parameter_index = imm[ctx.pc];
+    ctx.top[0].func().dynamic_parameter_name = const_string[imm[ctx.pc]];
 }
 
 inline void vm::o_lnot() {