diff --git a/README.md b/README.md
index e12c4b9..9dd3309 100644
--- a/README.md
+++ b/README.md
@@ -4,7 +4,7 @@
 
 ![GitHub code size](https://img.shields.io/github/languages/code-size/ValKmjolnir/Nasal-Interpreter?style=flat-square&logo=github)
 ![GitHub release(latest by date)](https://img.shields.io/github/v/release/ValKmjolnir/Nasal-Interpreter?style=flat-square&logo=github)
-![in dev](https://img.shields.io/badge/dev-v11.0-blue?style=flat-square&logo=github)
+![in dev](https://img.shields.io/badge/dev-v11.1-blue?style=flat-square&logo=github)
 [![license](https://img.shields.io/badge/license-GPLv2-green?style=flat-square&logo=github)](./LICENSE)
 
 > This document is also available in: [__中文__](./doc/README_zh.md) | [__English__](./README.md)
diff --git a/doc/README_zh.md b/doc/README_zh.md
index 8e5bf11..c1fb67f 100644
--- a/doc/README_zh.md
+++ b/doc/README_zh.md
@@ -4,7 +4,7 @@
 
 ![GitHub code size](https://img.shields.io/github/languages/code-size/ValKmjolnir/Nasal-Interpreter?style=flat-square&logo=github)
 ![GitHub release(latest by date)](https://img.shields.io/github/v/release/ValKmjolnir/Nasal-Interpreter?style=flat-square&logo=github)
-![in dev](https://img.shields.io/badge/dev-v11.0-blue?style=flat-square&logo=github)
+![in dev](https://img.shields.io/badge/dev-v11.1-blue?style=flat-square&logo=github)
 [![license](https://img.shields.io/badge/license-GPLv2-green?style=flat-square&logo=github)](../LICENSE)
 
 > 这篇文档包含多语言版本: [__中文__](../doc/README_zh.md) | [__English__](../README.md)
diff --git a/src/coroutine.cpp b/src/coroutine.cpp
index 332cf18..5df1397 100644
--- a/src/coroutine.cpp
+++ b/src/coroutine.cpp
@@ -28,7 +28,7 @@ var builtin_cocreate(var* local, gc& ngc) {
 
     cort.ctx.top[0] = nil;
     cort.ctx.localr = cort.ctx.top+1;
-    cort.ctx.top = cort.ctx.localr+func.func().lsize;
+    cort.ctx.top = cort.ctx.localr+func.func().local_size;
     cort.ctx.localr[0] = func.func().local[0];
     cort.ctx.top[0] = nil; // old upvalr
     cort.ctx.top++;
diff --git a/src/nasal.h b/src/nasal.h
index 6d4e15e..7b43271 100644
--- a/src/nasal.h
+++ b/src/nasal.h
@@ -1,7 +1,7 @@
 #pragma once
 
 #ifndef __nasver
-#define __nasver "11.0"
+#define __nasver "11.1"
 #endif
 
 #include <cstdint>
diff --git a/src/nasal_gc.cpp b/src/nasal_gc.cpp
index b85986d..193127a 100644
--- a/src/nasal_gc.cpp
+++ b/src/nasal_gc.cpp
@@ -93,7 +93,7 @@ std::ostream& operator<<(std::ostream& out, nas_hash& hash) {
 }
 
 void nas_func::clear() {
-    dpara = -1;
+    dynamic_parameter_index = -1;
     local.clear();
     upval.clear();
     keys.clear();
diff --git a/src/nasal_gc.h b/src/nasal_gc.h
index 590d1ed..af6ec61 100644
--- a/src/nasal_gc.h
+++ b/src/nasal_gc.h
@@ -146,22 +146,26 @@ struct nas_hash {
 };
 
 struct nas_func {
-    i32 dpara; // dynamic parameter name index in hash.
+    i32 dynamic_parameter_index; // dynamic parameter name index in hash.
     u32 entry; // pc will set to entry-1 to call this function
-    u32 psize; // used to load default parameters to a new function
-    u32 lsize; // used to expand memory space for local values on stack
+    u32 parameter_size; // used to load default parameters to a new function
+    u32 local_size; // used to expand memory space for local values on stack
     std::vector<var> local; // local scope with default value(var)
     std::vector<var> upval; // closure
-    std::unordered_map<u32,u32> keys; // parameter table, u32 begins from 1
 
-    nas_func(): dpara(-1), entry(0), psize(0), lsize(0) {}
+    // parameter table, u32 begins from 1
+    std::unordered_map<std::string, u32> keys;
+
+    nas_func():
+        dynamic_parameter_index(-1), entry(0),
+        parameter_size(0), local_size(0) {}
     void clear();
 };
 
 struct nas_upval {
 public:
     /* on stack, use these variables */
-    bool onstk;
+    bool on_stack;
     u32 size;
     var* stk;
 
@@ -169,14 +173,14 @@ public:
     std::vector<var> elems;
 
 public:
-    nas_upval(): onstk(true), size(0), stk(nullptr) {}
+    nas_upval(): on_stack(true), size(0), stk(nullptr) {}
 
     var& operator[](usize n) {
-        return onstk? stk[n]:elems[n];
+        return on_stack? stk[n]:elems[n];
     }
 
     void clear() {
-        onstk = true;
+        on_stack = true;
         elems.clear();
         size = 0;
     }
@@ -184,7 +188,7 @@ public:
 
 struct nas_ghost {
 private:
-    using destructor=void (*)(void*);
+    using destructor = void (*)(void*);
 
 public:
     std::string type_name;
diff --git a/src/nasal_vm.cpp b/src/nasal_vm.cpp
index 143e773..c42d6a8 100644
--- a/src/nasal_vm.cpp
+++ b/src/nasal_vm.cpp
@@ -188,10 +188,10 @@ void vm::gstate() {
 }
 
 void vm::lstate() {
-    if (!ctx.localr || !ctx.funcr.func().lsize) {
+    if (!ctx.localr || !ctx.funcr.func().local_size) {
         return;
     }
-    const u32 lsize = ctx.funcr.func().lsize;
+    const u32 lsize = ctx.funcr.func().local_size;
     std::clog << "local (0x" << std::hex << reinterpret_cast<u64>(ctx.localr)
               << " <+" << static_cast<u64>(ctx.localr-ctx.stack)
               << ">)\n" << std::dec;
@@ -228,6 +228,22 @@ void vm::detail() {
     ustate();
 }
 
+std::string vm::report_lack_arguments(u32 argc, const nas_func& func) const {
+    auto result = std::string("lack argument(s): ");
+    std::vector<std::string> argument_list = {};
+    argument_list.resize(func.keys.size());
+    for(const auto& i : func.keys) {
+        argument_list[i.second-1] = i.first;
+    }
+    for(u32 i = argc; i<argument_list.size(); ++i) {
+        result += argument_list[i];
+        if (i!=argument_list.size()-1) {
+            result += ", ";
+        }
+    }
+    return result;
+}
+
 void vm::die(const std::string& str) {
     std::cerr << "[vm] error: " << str << "\n";
     traceback();
diff --git a/src/nasal_vm.h b/src/nasal_vm.h
index ed7a042..278cb3d 100644
--- a/src/nasal_vm.h
+++ b/src/nasal_vm.h
@@ -65,6 +65,7 @@ protected:
     void lstate();
     void ustate();
     void detail();
+    std::string report_lack_arguments(u32, const nas_func&) const;
     void die(const std::string&);
 
     /* vm calculation functions*/
@@ -204,7 +205,7 @@ inline void vm::o_repl() {
 
 inline void vm::o_intl() {
     ctx.top[0].func().local.resize(imm[ctx.pc], nil);
-    ctx.top[0].func().lsize = imm[ctx.pc];
+    ctx.top[0].func().local_size = imm[ctx.pc];
 }
 
 inline void vm::o_loadg() {
@@ -217,7 +218,7 @@ inline void vm::o_loadl() {
 
 inline void vm::o_loadu() {
     ctx.funcr.func().upval[(imm[ctx.pc]>>16)&0xffff]
-         .upval()[imm[ctx.pc]&0xffff] = (ctx.top--)[0];
+                    .upval()[imm[ctx.pc]&0xffff] = (ctx.top--)[0];
 }
 
 inline void vm::o_pnum() {
@@ -252,7 +253,7 @@ inline void vm::o_newf() {
     (++ctx.top)[0] = ngc.alloc(vm_func);
     auto& func = ctx.top[0].func();
     func.entry = imm[ctx.pc];
-    func.psize = 1;
+    func.parameter_size = 1;
 
     /* this means you create a new function in local scope */
     if (ctx.localr) {
@@ -260,7 +261,7 @@ inline void vm::o_newf() {
         // function created in the same local scope shares one closure
         // so this size & stk setting has no problem
         var upval = (ctx.upvalr.type==vm_nil)? ngc.alloc(vm_upval):ctx.upvalr;
-        upval.upval().size = ctx.funcr.func().lsize;
+        upval.upval().size = ctx.funcr.func().local_size;
         upval.upval().stk = ctx.localr;
         func.upval.push_back(upval);
         ctx.upvalr = upval;
@@ -275,20 +276,20 @@ inline void vm::o_happ() {
 inline void vm::o_para() {
     auto& func = ctx.top[0].func();
     // func->size has 1 place reserved for "me"
-    func.keys[imm[ctx.pc]] = func.psize;
-    func.local[func.psize++] = var::none();
+    func.keys[cstr[imm[ctx.pc]]] = func.parameter_size;
+    func.local[func.parameter_size++] = var::none();
 }
 
 inline void vm::o_deft() {
     var val = ctx.top[0];
     auto& func = (--ctx.top)[0].func();
     // func->size has 1 place reserved for "me"
-    func.keys[imm[ctx.pc]] = func.psize;
-    func.local[func.psize++] = val;
+    func.keys[cstr[imm[ctx.pc]]] = func.parameter_size;
+    func.local[func.parameter_size++] = val;
 }
 
 inline void vm::o_dyn() {
-    ctx.top[0].func().dpara = imm[ctx.pc];
+    ctx.top[0].func().dynamic_parameter_index = imm[ctx.pc];
 }
 
 inline void vm::o_lnot() {
@@ -349,6 +350,7 @@ inline void vm::o_sub() {op_calc(-);}
 inline void vm::o_mul() {op_calc(*);}
 inline void vm::o_div() {op_calc(/);}
 inline void vm::o_lnk() {
+    // concat two vectors into one
     if (ctx.top[-1].type==vm_vec && ctx.top[0].type==vm_vec) {
         ngc.temp = ngc.alloc(vm_vec);
         for(auto i : ctx.top[-1].vec().elems) {
@@ -362,6 +364,7 @@ inline void vm::o_lnk() {
         --ctx.top;
         return;
     }
+    // concat strings
     ctx.top[-1] = ngc.newstr(ctx.top[-1].tostr()+ctx.top[0].tostr());
     --ctx.top;
 }
@@ -607,7 +610,7 @@ inline void vm::o_callv() {
             ctx.top[0].func().local[0] = val; // 'me'
         }
     } else if (vec.type==vm_str) {
-        auto& str = vec.str();
+        const auto& str = vec.str();
         i32 num = val.tonum();
         i32 len = str.length();
         if (num<-len || num>=len) {
@@ -670,13 +673,13 @@ inline void vm::o_callh() {
 }
 
 inline void vm::o_callfv() {
-    u32 argc = imm[ctx.pc]; // arguments counter
+    const u32 argc = imm[ctx.pc]; // arguments counter
     var* local = ctx.top-argc+1; // arguments begin address
     if (local[-1].type!=vm_func) {
         die("must call a function");
         return;
     }
-    auto& func = local[-1].func();
+    const auto& func = local[-1].func();
 
     // swap funcr with local[-1]
     var tmp = local[-1];
@@ -684,27 +687,29 @@ inline void vm::o_callfv() {
     ctx.funcr = tmp;
 
     // top-argc+lsize(local) +1(old pc) +1(old localr) +1(old upvalr)
-    if (ctx.top-argc+func.lsize+3>=ctx.canary) {
+    if (ctx.top-argc+func.local_size+3>=ctx.canary) {
         die("stack overflow");
         return;
     }
     // parameter size is func->psize-1, 1 is reserved for "me"
-    u32 psize = func.psize-1;
-    if (argc<psize && func.local[argc+1].type==vm_none) {
-        die("lack argument(s)");
+    const u32 parameter_size = func.parameter_size-1;
+    if (argc<parameter_size && func.local[argc+1].type==vm_none) {
+        die(report_lack_arguments(argc, func));
         return;
     }
 
+    // load dynamic argument, default nil, for better performance
     var dynamic = nil;
-    if (func.dpara>=0) { // load dynamic arguments
+    if (func.dynamic_parameter_index>=0) {
+        // load dynamic argument
         dynamic = ngc.alloc(vm_vec);
-        for(u32 i = psize; i<argc; ++i) {
+        for(u32 i = parameter_size; i<argc; ++i) {
             dynamic.vec().elems.push_back(local[i]);
         }
-    } else if (psize<argc) {
-        // load arguments to "arg", located at stack+1
+    } else if (parameter_size<argc) {
+        // load arguments to default dynamic argument "arg", located at stack+1
         dynamic = ngc.alloc(vm_vec);
-        for(u32 i = psize; i<argc; ++i) {
+        for(u32 i = parameter_size; i<argc; ++i) {
             dynamic.vec().elems.push_back(local[i]);
         }
     }
@@ -713,19 +718,21 @@ inline void vm::o_callfv() {
     // then all the available values the vector needs
     // are all outside the stack top and may be
     // collected incorrectly
-    ctx.top = local+func.lsize;
+    ctx.top = local+func.local_size;
 
-    u32 min_size = (std::min)(psize, argc); // avoid error in MSVC
+    const u32 min_size = (std::min)(parameter_size, argc); // avoid error in MSVC
     for(u32 i = min_size; i>=1; --i) { // load arguments
         local[i] = local[i-1];
     }
     local[0] = func.local[0];// load "me"
 
     // load local scope & default arguments
-    for(u32 i = min_size+1; i<func.lsize; ++i) {
+    for(u32 i = min_size+1; i<func.local_size; ++i) {
         local[i] = func.local[i];
     }
-    local[func.dpara>=0? psize+1:func.lsize-1] = dynamic;
+    // load dynamic argument
+    local[func.dynamic_parameter_index>=0?
+          parameter_size+1:func.local_size-1] = dynamic;
 
     ctx.top[0] = ctx.upvalr;
     (++ctx.top)[0] = var::addr(ctx.localr);
@@ -736,41 +743,56 @@ inline void vm::o_callfv() {
 }
 
 inline void vm::o_callfh() {
-    auto& hash = ctx.top[0].hash().elems;
+    const auto& hash = ctx.top[0].hash().elems;
     if (ctx.top[-1].type!=vm_func) {
         die("must call a function");
         return;
     }
-    auto& func = ctx.top[-1].func();
+    const auto& func = ctx.top[-1].func();
     var tmp = ctx.top[-1];
     ctx.top[-1] = ctx.funcr;
     ctx.funcr = tmp;
 
     // top -1(hash) +lsize(local) +1(old pc) +1(old localr) +1(old upvalr)
-    if (ctx.top+func.lsize+2>= ctx.canary) {
+    if (ctx.top+func.local_size+2>= ctx.canary) {
         die("stack overflow");
         return;
     }
-    if (func.dpara>=0) {
-        die("special call cannot use dynamic argument");
+    // dynamic parameter is not allowed in this kind of function call
+    if (func.dynamic_parameter_index>=0) {
+        die("special call cannot use dynamic argument \"" +
+            cstr[func.dynamic_parameter_index] + "\""
+        );
         return;
     }
 
     var* local = ctx.top;
-    ctx.top += func.lsize;
-    for(u32 i = 0; i<func.lsize; ++i) {
+    ctx.top += func.local_size;
+    for(u32 i = 0; i<func.local_size; ++i) {
         local[i] = func.local[i];
     }
     
+    bool lack_arguments_flag = false;
     for(const auto& i : func.keys) {
-        auto& key = cstr[i.first];
+        const auto& key = i.first;
         if (hash.count(key)) {
-            local[i.second] = hash[key];
+            local[i.second] = hash.at(key);
         } else if (local[i.second].type==vm_none) {
-            die("lack argument(s): \""+key+"\"");
-            return;
+            lack_arguments_flag = true;
         }
     }
+    if (lack_arguments_flag) {
+        auto info = std::string("lack argument(s): ");
+        for(const auto& i : func.keys) {
+            const auto& key = i.first;
+            if (local[i.second].type==vm_none) {
+                info += key + ", ";
+            }
+        }
+        info = info.substr(0, info.length()-2);
+        die(info);
+        return;
+    }
 
     ctx.top[0] = ctx.upvalr;
     (++ctx.top)[0] = var::addr(ctx.localr);
@@ -831,7 +853,7 @@ inline void vm::o_slc() {
 inline void vm::o_slc2() {
     var val2 = (ctx.top--)[0];
     var val1 = (ctx.top--)[0];
-    auto& ref = ctx.top[-1].vec().elems;
+    const auto& ref = ctx.top[-1].vec().elems;
     auto& aim = ctx.top[0].vec().elems;
 
     u8 type1 = val1.type,type2=val2.type;
@@ -875,8 +897,9 @@ inline void vm::o_mcalll() {
 inline void vm::o_mupval() {
     ctx.memr = &(
         ctx.funcr.func()
-            .upval[(imm[ctx.pc]>>16)&0xffff]
-            .upval()[imm[ctx.pc]&0xffff]);
+           .upval[(imm[ctx.pc]>>16)&0xffff]
+           .upval()[imm[ctx.pc]&0xffff]
+    );
     (++ctx.top)[0] = ctx.memr[0];
     // push value in this memory space on stack
     // to avoid being garbage collected
@@ -897,7 +920,7 @@ inline void vm::o_mcallv() {
             return;
         }
         auto& ref = vec.hash();
-        auto& str = val.str();
+        const auto& str = val.str();
         ctx.memr = ref.get_mem(str);
         if (!ctx.memr) {
             ref.elems[str] = nil;
@@ -909,7 +932,7 @@ inline void vm::o_mcallv() {
             return;
         }
         auto& ref = vec.map();
-        auto& str = val.str();
+        const auto& str = val.str();
         ctx.memr = ref.get_mem(str);
         if (!ctx.memr) {
             die("cannot find symbol \"" + str + "\"");
@@ -926,7 +949,7 @@ inline void vm::o_mcallh() {
         die("must call a hash");
         return;
     }
-    auto& str = cstr[imm[ctx.pc]];
+    const auto& str = cstr[imm[ctx.pc]];
     if (hash.type==vm_map) {
         ctx.memr = hash.map().get_mem(str);
         if (!ctx.memr) {
@@ -936,7 +959,8 @@ inline void vm::o_mcallh() {
     }
     auto& ref = hash.hash();
     ctx.memr = ref.get_mem(str);
-    if (!ctx.memr) { // create a new key
+    // create a new key
+    if (!ctx.memr) {
         ref.elems[str] = nil;
         ctx.memr = ref.get_mem(str);
     }
@@ -970,10 +994,11 @@ inline void vm::o_ret() {
     ctx.funcr = ctx.top[0];
     ctx.top[0] = ret; // rewrite func with returned value
 
-    if (up.type==vm_upval) { // synchronize upvalue
+    // synchronize upvalue
+    if (up.type==vm_upval) {
         auto& upval = up.upval();
-        auto size = func.func().lsize;
-        upval.onstk = false;
+        auto size = func.func().local_size;
+        upval.on_stack = false;
         upval.elems.resize(size);
         for(u32 i = 0; i<size; ++i) {
             upval.elems[i] = local[i];