diff --git a/doc/namespace.md b/doc/namespace.md
new file mode 100644
index 0000000..de183f3
--- /dev/null
+++ b/doc/namespace.md
@@ -0,0 +1,64 @@
+# Nasal Namespace
+
+![feigenbaum](./pic/feigenbaum.png)
+
+## Introduction
+
+In this nasal interpreter,
+we use this way below to construct namespaces:
+
+- library is linked directly with the script
+- module is wraped by a function generated by linker, and return a hash
+
+## Library
+
+Library file is linked with script file directly, like this:
+
+In `std/lib.nas`:
+
+```nasal
+var a = 1;
+```
+
+In `example.nas`:
+
+```nasal
+var b = 1;
+```
+
+At the link stage,
+in fact we put the ast of two files together to make a new ast,
+so the result is equal to:
+
+```nasal
+var a = 1;
+var b = 1;
+```
+
+## Module
+
+Modules is wraped up by a function,
+and return a hash, for example:
+
+In `std/example_module.nas`:
+
+```nasal
+var a = 1;
+```
+
+We analysed this file and generated the ast.
+Then we find all the global symbols.
+At last we use the information of all the globals symbols in this file to generate a hash to return.
+
+So the result is equal to:
+
+```nasal
+var example_module = func {
+    # source code begin
+    var a = 1;
+    # source code end
+    return {
+        a: a
+    };
+}();
+```
diff --git a/module/libfib.nas b/module/libfib.nas
index 7fe2a1c..889cff1 100644
--- a/module/libfib.nas
+++ b/module/libfib.nas
@@ -1,3 +1,4 @@
+
 var libfib=func(){
     var dl=dylib.dlopen("libfib."~(os.platform()=="windows"?"dll":"so"));
     var fib=dl.fib;
diff --git a/src/ast_dumper.cpp b/src/ast_dumper.cpp
index a549ded..84f62f2 100644
--- a/src/ast_dumper.cpp
+++ b/src/ast_dumper.cpp
@@ -2,13 +2,6 @@
 
 #include <iostream>
 
-bool ast_dumper::visit_file_info(file_info* node) {
-    dump_indent();
-    std::cout << "file \"" << node->get_file_name() << "\"";
-    std::cout << format_location(node->get_location());
-    return true;
-}
-
 bool ast_dumper::visit_null_expr(null_expr* node) {
     dump_indent();
     std::cout << "null" << format_location(node->get_location());
diff --git a/src/ast_dumper.h b/src/ast_dumper.h
index cb9bcb9..1f520d2 100644
--- a/src/ast_dumper.h
+++ b/src/ast_dumper.h
@@ -39,7 +39,6 @@ private:
     }
 
 public:
-    bool visit_file_info(file_info*) override;
     bool visit_null_expr(null_expr*) override;
     bool visit_nil_expr(nil_expr*) override;
     bool visit_number_literal(number_literal*) override;
diff --git a/src/ast_visitor.cpp b/src/ast_visitor.cpp
index 8757e63..d9aa45a 100644
--- a/src/ast_visitor.cpp
+++ b/src/ast_visitor.cpp
@@ -10,10 +10,6 @@ bool ast_visitor::visit_call(call* node) {
     return true;
 }
 
-bool ast_visitor::visit_file_info(file_info* node) {
-    return true;
-}
-
 bool ast_visitor::visit_null_expr(null_expr* node) {
     return true;
 }
diff --git a/src/ast_visitor.h b/src/ast_visitor.h
index 932c912..9586633 100644
--- a/src/ast_visitor.h
+++ b/src/ast_visitor.h
@@ -6,7 +6,6 @@ class ast_visitor {
 public:
     virtual bool visit_expr(expr*);
     virtual bool visit_call(call*);
-    virtual bool visit_file_info(file_info*);
     virtual bool visit_null_expr(null_expr*);
     virtual bool visit_nil_expr(nil_expr*);
     virtual bool visit_number_literal(number_literal*);
diff --git a/src/nasal_ast.cpp b/src/nasal_ast.cpp
index 03c8f14..5b2610c 100644
--- a/src/nasal_ast.cpp
+++ b/src/nasal_ast.cpp
@@ -9,10 +9,6 @@ void call::accept(ast_visitor* visitor) {
     visitor->visit_call(this);
 }
 
-void file_info::accept(ast_visitor* visitor) {
-    visitor->visit_file_info(this);
-}
-
 void null_expr::accept(ast_visitor* visitor) {
     visitor->visit_null_expr(this);
 }
diff --git a/src/nasal_ast.h b/src/nasal_ast.h
index b7c0ca8..ffffd95 100644
--- a/src/nasal_ast.h
+++ b/src/nasal_ast.h
@@ -8,7 +8,6 @@
 
 enum class expr_type:u32 {
     ast_null = 0,    // null node
-    ast_file_info,   // stores file info
     ast_block,       // code block 
     ast_nil,         // nil keyword
     ast_num,         // number, basic value type
@@ -84,21 +83,6 @@ public:
     virtual void accept(ast_visitor*);
 };
 
-class file_info:public expr {
-private:
-    uint16_t index;
-    std::string filename;
-
-public:
-    file_info(const span& location, uint16_t file_index, const std::string& name):
-        expr(location, expr_type::ast_file_info),
-        index(file_index), filename(name) {}
-    ~file_info() = default;
-    uint16_t get_index() const {return index;}
-    const std::string& get_file_name() const {return filename;}
-    void accept(ast_visitor*) override;
-};
-
 class null_expr:public expr {
 public:
     null_expr(const span& location):
diff --git a/src/nasal_codegen.cpp b/src/nasal_codegen.cpp
index bd38dc7..7940890 100644
--- a/src/nasal_codegen.cpp
+++ b/src/nasal_codegen.cpp
@@ -100,42 +100,44 @@ i32 codegen::upvalue_find(const std::string& name) {
     return index;
 }
 
-void codegen::gen(u8 operation_code, u32 num, u32 line) {
-    code.push_back({operation_code, fileindex, num, line});
+void codegen::gen(u8 operation_code, u32 num, const span& loc) {
+    code.push_back({operation_code,
+        static_cast<u16>(file_map.at(loc.file)),
+        num, loc.begin_line});
 }
 
 void codegen::num_gen(number_literal* node) {
     f64 num = node->get_number();
     regist_num(num);
-    gen(op_pnum,const_number_map.at(num), node->get_line());
+    gen(op_pnum, const_number_map.at(num), node->get_location());
 }
 
 void codegen::str_gen(string_literal* node) {
     const auto& str = node->get_content();
     regist_str(str);
-    gen(op_pstr, const_string_map.at(str), node->get_line());
+    gen(op_pstr, const_string_map.at(str), node->get_location());
 }
 
 void codegen::bool_gen(bool_literal* node) {
     f64 num = node->get_flag()? 1:0;
     regist_num(num);
-    gen(op_pnum, const_number_map.at(num), node->get_line());
+    gen(op_pnum, const_number_map.at(num), node->get_location());
 }
 
 void codegen::vec_gen(vector_expr* node) {
     for(auto child : node->get_elements()) {
         calc_gen(child);
     }
-    gen(op_newv, node->get_elements().size(), node->get_line());
+    gen(op_newv, node->get_elements().size(), node->get_location());
 }
 
 void codegen::hash_gen(hash_expr* node) {
-    gen(op_newh, 0, node->get_line());
+    gen(op_newh, 0, node->get_location());
     for(auto child : node->get_members()) {
         calc_gen(child->get_value());
         const auto& field_name = child->get_name();
         regist_str(field_name);
-        gen(op_happ, const_string_map.at(field_name), child->get_line());
+        gen(op_happ, const_string_map.at(field_name), child->get_location());
     }
 }
 
@@ -175,9 +177,9 @@ void codegen::func_gen(function* node) {
     }
 
     usize newf=code.size();
-    gen(op_newf, 0, node->get_line());
+    gen(op_newf, 0, node->get_location());
     usize lsize=code.size();
-    gen(op_intl, 0, node->get_line());
+    gen(op_intl, 0, node->get_location());
     
     // add special keyword 'me' into symbol table
     // this symbol is only used in local scope(function's scope)
@@ -196,14 +198,14 @@ void codegen::func_gen(function* node) {
         regist_str(name);
         switch(tmp->get_parameter_type()) {
             case parameter::param_type::normal_parameter:
-                gen(op_para, const_string_map.at(name), tmp->get_line());
+                gen(op_para, const_string_map.at(name), tmp->get_location());
                 break;
             case parameter::param_type::default_parameter:
                 calc_gen(tmp->get_default_value());
-                gen(op_deft, const_string_map.at(name), tmp->get_line());
+                gen(op_deft, const_string_map.at(name), tmp->get_location());
                 break;
             case parameter::param_type::dynamic_parameter:
-                gen(op_dyn, const_string_map.at(name), tmp->get_line());
+                gen(op_dyn, const_string_map.at(name), tmp->get_location());
                 break;
         }
         add_symbol(name);
@@ -211,7 +213,7 @@ void codegen::func_gen(function* node) {
 
     code[newf].num = code.size()+1; // entry
     usize jmp_ptr = code.size();
-    gen(op_jmp, 0, node->get_line());
+    gen(op_jmp, 0, node->get_location());
 
     auto block = node->get_code_block();
     // search symbols first, must use after loading parameters
@@ -244,8 +246,8 @@ void codegen::func_gen(function* node) {
 
     if (!block->get_expressions().size() ||
         block->get_expressions().back()->get_type()!=expr_type::ast_ret) {
-        gen(op_pnil, 0, block->get_line());
-        gen(op_ret, 0, block->get_line());
+        gen(op_pnil, 0, block->get_location());
+        gen(op_ret, 0, block->get_location());
     }
     code[jmp_ptr].num = code.size();
 }
@@ -269,7 +271,7 @@ void codegen::call_id(identifier* node) {
     const auto& name = node->get_name();
     for(u32 i = 0; builtin[i].name; ++i) {
         if (builtin[i].name==name) {
-            gen(op_callb, i, node->get_line());
+            gen(op_callb, i, node->get_location());
             if (local.empty()) {
                 die("should warp native function in local scope",
                     node->get_location());
@@ -279,15 +281,15 @@ void codegen::call_id(identifier* node) {
     }
     i32 index;
     if ((index=local_find(name))>=0) {
-        gen(op_calll, index, node->get_line());
+        gen(op_calll, index, node->get_location());
         return;
     }
     if ((index=upvalue_find(name))>=0) {
-        gen(op_upval, index, node->get_line());
+        gen(op_upval, index, node->get_location());
         return;
     }
     if ((index=global_find(name))>=0) {
-        gen(op_callg, index, node->get_line());
+        gen(op_callg, index, node->get_location());
         return;
     }
     die("undefined symbol \"" + name + "\"", node->get_location());
@@ -295,7 +297,7 @@ void codegen::call_id(identifier* node) {
 
 void codegen::call_hash_gen(call_hash* node) {
     regist_str(node->get_field());
-    gen(op_callh, const_string_map.at(node->get_field()), node->get_line());
+    gen(op_callh, const_string_map.at(node->get_field()), node->get_location());
 }
 
 void codegen::call_vector_gen(call_vector* node) {
@@ -303,39 +305,39 @@ void codegen::call_vector_gen(call_vector* node) {
     if (node->get_slices().size()==1 &&
         !node->get_slices()[0]->get_end()) {
         calc_gen(node->get_slices()[0]->get_begin());
-        gen(op_callv, 0, node->get_slices()[0]->get_line());
+        gen(op_callv, 0, node->get_slices()[0]->get_location());
         return;
     }
-    gen(op_slcbeg, 0, node->get_line());
+    gen(op_slcbeg, 0, node->get_location());
     for(auto tmp : node->get_slices()) {
         if (!tmp->get_end()) {
             calc_gen(tmp->get_begin());
-            gen(op_slc, 0, tmp->get_line());
+            gen(op_slc, 0, tmp->get_location());
         } else {
             calc_gen(tmp->get_begin());
             calc_gen(tmp->get_end());
-            gen(op_slc2, 0, tmp->get_line());
+            gen(op_slc2, 0, tmp->get_location());
         }
     }
-    gen(op_slcend, 0, node->get_line());
+    gen(op_slcend, 0, node->get_location());
 }
 
 void codegen::call_func_gen(call_function* node) {
     if (node->get_argument().size() &&
         node->get_argument()[0]->get_type()==expr_type::ast_pair) {
-        gen(op_newh, 0, node->get_line());
+        gen(op_newh, 0, node->get_location());
         for(auto child : node->get_argument()) {
             calc_gen(((hash_pair*)child)->get_value());
             const auto& field_name = ((hash_pair*)child)->get_name();
             regist_str(field_name);
-            gen(op_happ, const_string_map.at(field_name), child->get_line());
+            gen(op_happ, const_string_map.at(field_name), child->get_location());
         }
-        gen(op_callfh, 0, node->get_line());
+        gen(op_callfh, 0, node->get_location());
     } else {
         for(auto child : node->get_argument()) {
             calc_gen(child);
         }
-        gen(op_callfv, node->get_argument().size(), node->get_line());
+        gen(op_callfv, node->get_argument().size(), node->get_location());
     }
 }
 
@@ -390,15 +392,15 @@ void codegen::mcall_id(identifier* node) {
     }
     i32 index;
     if ((index=local_find(name))>=0) {
-        gen(op_mcalll, index, node->get_line());
+        gen(op_mcalll, index, node->get_location());
         return;
     }
     if ((index=upvalue_find(name))>=0) {
-        gen(op_mupval, index, node->get_line());
+        gen(op_mupval, index, node->get_location());
         return;
     }
     if ((index=global_find(name))>=0) {
-        gen(op_mcallg, index, node->get_line());
+        gen(op_mcallg, index, node->get_location());
         return;
     }
     die("undefined symbol \"" + name + "\"", node->get_location());
@@ -415,20 +417,20 @@ void codegen::mcall_vec(call_vector* node) {
         return;
     }
     calc_gen(call->get_begin());
-    gen(op_mcallv, 0, node->get_line());
+    gen(op_mcallv, 0, node->get_location());
 }
 
 void codegen::mcall_hash(call_hash* node) {
     regist_str(node->get_field());
-    gen(op_mcallh, const_string_map.at(node->get_field()), node->get_line());
+    gen(op_mcallh, const_string_map.at(node->get_field()), node->get_location());
 }
 
 void codegen::single_def(definition_expr* node) {
     const auto& str = node->get_variable_name()->get_name();
     calc_gen(node->get_value());
     local.empty()?
-        gen(op_loadg, global_find(str), node->get_line()):
-        gen(op_loadl, local_find(str), node->get_line());
+        gen(op_loadg, global_find(str), node->get_location()):
+        gen(op_loadl, local_find(str), node->get_location());
 }
 
 void codegen::multi_def(definition_expr* node) {
@@ -448,21 +450,21 @@ void codegen::multi_def(definition_expr* node) {
             calc_gen(vals[i]);
             const auto& name = identifiers[i]->get_name();
             local.empty()?
-                gen(op_loadg, global_find(name), identifiers[i]->get_line()):
-                gen(op_loadl, local_find(name), identifiers[i]->get_line());
+                gen(op_loadg, global_find(name), identifiers[i]->get_location()):
+                gen(op_loadl, local_find(name), identifiers[i]->get_location());
         }
         return;
     }
     // (var a,b,c) = [0,1,2];
     calc_gen(node->get_value());
     for(usize i = 0; i<size; ++i) {
-        gen(op_callvi, i, node->get_value()->get_line());
+        gen(op_callvi, i, node->get_value()->get_location());
         const auto& name = identifiers[i]->get_name();
         local.empty()?
-            gen(op_loadg, global_find(name), identifiers[i]->get_line()):
-            gen(op_loadl, local_find(name), identifiers[i]->get_line());
+            gen(op_loadg, global_find(name), identifiers[i]->get_location()):
+            gen(op_loadl, local_find(name), identifiers[i]->get_location());
     }
-    gen(op_pop, 0, node->get_line());
+    gen(op_pop, 0, node->get_location());
 }
 
 void codegen::def_gen(definition_expr* node) {
@@ -477,7 +479,7 @@ void codegen::assignment_expression(assignment_expr* node) {
         case assignment_expr::assign_type::equal:
             calc_gen(node->get_right());
             mcall(node->get_left());
-            gen(op_meq, 0, node->get_line());
+            gen(op_meq, 0, node->get_location());
             break;
         case assignment_expr::assign_type::add_equal:
             if (node->get_right()->get_type()!=expr_type::ast_num) {
@@ -485,11 +487,11 @@ void codegen::assignment_expression(assignment_expr* node) {
             }
             mcall(node->get_left());
             if (node->get_right()->get_type()!=expr_type::ast_num) {
-                gen(op_addeq, 0, node->get_line());
+                gen(op_addeq, 0, node->get_location());
             } else {
                 auto num = ((number_literal*)node->get_right())->get_number();
                 regist_num(num);
-                gen(op_addeqc, const_number_map[num], node->get_line());
+                gen(op_addeqc, const_number_map[num], node->get_location());
             }
             break;
         case assignment_expr::assign_type::sub_equal:
@@ -498,11 +500,11 @@ void codegen::assignment_expression(assignment_expr* node) {
             }
             mcall(node->get_left());
             if (node->get_right()->get_type()!=expr_type::ast_num) {
-                gen(op_subeq, 0, node->get_line());
+                gen(op_subeq, 0, node->get_location());
             } else {
                 auto num = ((number_literal*)node->get_right())->get_number();
                 regist_num(num);
-                gen(op_subeqc, const_number_map[num], node->get_line());
+                gen(op_subeqc, const_number_map[num], node->get_location());
             }
             break;
         case assignment_expr::assign_type::mult_equal:
@@ -511,11 +513,11 @@ void codegen::assignment_expression(assignment_expr* node) {
             }
             mcall(node->get_left());
             if (node->get_right()->get_type()!=expr_type::ast_num) {
-                gen(op_muleq, 0, node->get_line());
+                gen(op_muleq, 0, node->get_location());
             } else {
                 auto num = ((number_literal*)node->get_right())->get_number();
                 regist_num(num);
-                gen(op_muleqc, const_number_map[num], node->get_line());
+                gen(op_muleqc, const_number_map[num], node->get_location());
             }
             break;
         case assignment_expr::assign_type::div_equal:
@@ -524,11 +526,11 @@ void codegen::assignment_expression(assignment_expr* node) {
             }
             mcall(node->get_left());
             if (node->get_right()->get_type()!=expr_type::ast_num) {
-                gen(op_diveq, 0, node->get_line());
+                gen(op_diveq, 0, node->get_location());
             } else {
                 auto num = ((number_literal*)node->get_right())->get_number();
                 regist_num(num);
-                gen(op_diveqc, const_number_map[num], node->get_line());
+                gen(op_diveqc, const_number_map[num], node->get_location());
             }
             break;
         case assignment_expr::assign_type::concat_equal:
@@ -537,27 +539,27 @@ void codegen::assignment_expression(assignment_expr* node) {
             }
             mcall(node->get_left());
             if (node->get_right()->get_type()!=expr_type::ast_str) {
-                gen(op_lnkeq, 0, node->get_line());
+                gen(op_lnkeq, 0, node->get_location());
             } else {
                 const auto& str = ((string_literal*)node->get_right())->get_content();
                 regist_str(str);
-                gen(op_lnkeqc, const_string_map[str], node->get_line());
+                gen(op_lnkeqc, const_string_map[str], node->get_location());
             }
             break;
         case assignment_expr::assign_type::bitwise_and_equal:
             calc_gen(node->get_right());
             mcall(node->get_left());
-            gen(op_btandeq, 0, node->get_line());
+            gen(op_btandeq, 0, node->get_location());
             break;
         case assignment_expr::assign_type::bitwise_or_equal:
             calc_gen(node->get_right());
             mcall(node->get_left());
-            gen(op_btoreq, 0, node->get_line());
+            gen(op_btoreq, 0, node->get_location());
             break;
         case assignment_expr::assign_type::bitwise_xor_equal:
             calc_gen(node->get_right());
             mcall(node->get_left());
-            gen(op_btxoreq, 0, node->get_line());
+            gen(op_btxoreq, 0, node->get_location());
             break;
     }
 }
@@ -581,7 +583,7 @@ void codegen::assignment_statement(assignment_expr* node) {
                 if (code.back().op==op_meq) {
                     code.back().num=1;
                 } else {
-                    gen(op_pop, 0, node->get_line());
+                    gen(op_pop, 0, node->get_location());
                 }
             }
             break;
@@ -599,7 +601,7 @@ void codegen::assignment_statement(assignment_expr* node) {
             } else if (op_addeqc<=code.back().op && code.back().op<=op_lnkeqc) {
                 code.back().op=code.back().op-op_addeqc+op_addecp;
             } else {
-                gen(op_pop, 0, node->get_line());
+                gen(op_pop, 0, node->get_location());
             }
             break;
     }
@@ -630,7 +632,7 @@ void codegen::multi_assign_gen(multi_assign* node) {
             } else if (code.back().op==op_mcallg) {
                 code.back().op=op_loadg;
             } else {
-                gen(op_meq, 1, tuple[i]->get_line());
+                gen(op_meq, 1, tuple[i]->get_location());
             }
         }
         return;
@@ -638,7 +640,7 @@ void codegen::multi_assign_gen(multi_assign* node) {
     calc_gen(node->get_value());
     auto& tuple = node->get_tuple()->get_elements();
     for(i32 i = 0; i<size; ++i) {
-        gen(op_callvi, i, node->get_value()->get_line());
+        gen(op_callvi, i, node->get_value()->get_location());
         // multi assign user loadl and loadg to avoid meq's stack--
         // and this operation changes local and global value directly
         mcall(tuple[i]);
@@ -649,35 +651,35 @@ void codegen::multi_assign_gen(multi_assign* node) {
         } else if (code.back().op==op_mcallg) {
             code.back().op=op_loadg;
         } else {
-            gen(op_meq, 1, tuple[i]->get_line());
+            gen(op_meq, 1, tuple[i]->get_location());
         }
     }
-    gen(op_pop, 0, node->get_line());
+    gen(op_pop, 0, node->get_location());
 }
 
 void codegen::cond_gen(condition_expr* node) {
     std::vector<usize> jmp_label;
     calc_gen(node->get_if_statement()->get_condition());
     auto ptr = code.size();
-    gen(op_jf, 0, node->get_if_statement()->get_line());
+    gen(op_jf, 0, node->get_if_statement()->get_location());
     block_gen(node->get_if_statement()->get_code_block());
     if (node->get_elsif_stataments().size() ||
         node->get_else_statement()) {
         jmp_label.push_back(code.size());
-        gen(op_jmp, 0, node->get_if_statement()->get_line());
+        gen(op_jmp, 0, node->get_if_statement()->get_location());
     }
     code[ptr].num = code.size();
 
     for(auto tmp : node->get_elsif_stataments()) {
         calc_gen(tmp->get_condition());
         ptr = code.size();
-        gen(op_jf, 0, tmp->get_line());
+        gen(op_jf, 0, tmp->get_location());
         block_gen(tmp->get_code_block());
         // the last condition doesn't need to jmp
         if (tmp!=node->get_elsif_stataments().back() ||
             node->get_else_statement()) {
             jmp_label.push_back(code.size());
-            gen(op_jmp, 0, tmp->get_line());
+            gen(op_jmp, 0, tmp->get_location());
         }
         code[ptr].num=code.size();
     }
@@ -719,10 +721,10 @@ void codegen::while_gen(while_expr* node) {
     usize loop_ptr = code.size();
     calc_gen(node->get_condition());
     usize condition_ptr = code.size();
-    gen(op_jf, 0, node->get_condition()->get_line());
+    gen(op_jf, 0, node->get_condition()->get_location());
 
     block_gen(node->get_code_block());
-    gen(op_jmp, loop_ptr, node->get_code_block()->get_line());
+    gen(op_jmp, loop_ptr, node->get_code_block()->get_location());
     code[condition_ptr].num = code.size();
     load_continue_break(code.size()-1, code.size());
 }
@@ -732,17 +734,17 @@ void codegen::for_gen(for_expr* node) {
     usize jmp_place = code.size();
     if (node->get_condition()->get_type()==expr_type::ast_null) {
         regist_num(1);
-        gen(op_pnum, const_number_map.at(1), node->get_condition()->get_line());
+        gen(op_pnum, const_number_map.at(1), node->get_condition()->get_location());
     } else {
         calc_gen(node->get_condition());
     }
     usize label_exit = code.size();
-    gen(op_jf, 0, node->get_condition()->get_line());
+    gen(op_jf, 0, node->get_condition()->get_location());
 
     block_gen(node->get_code_block());
     usize continue_place = code.size();
     statement_generation(node->get_step());
-    gen(op_jmp, jmp_place, node->get_step()->get_line());
+    gen(op_jmp, jmp_place, node->get_step()->get_location());
     code[label_exit].num = code.size();
 
     load_continue_break(continue_place, code.size());
@@ -750,19 +752,19 @@ void codegen::for_gen(for_expr* node) {
 
 void codegen::forei_gen(forei_expr* node) {
     calc_gen(node->get_value());
-    gen(op_cnt, 0, node->get_value()->get_line());
+    gen(op_cnt, 0, node->get_value()->get_location());
     usize ptr = code.size();
     if (node->get_loop_type()==forei_expr::forei_loop_type::forindex) {
-        gen(op_findex, 0, node->get_line());
+        gen(op_findex, 0, node->get_location());
     } else {
-        gen(op_feach, 0, node->get_line());
+        gen(op_feach, 0, node->get_location());
     }
     if (node->get_iterator()->get_name()) { // define a new iterator
         auto name_node = node->get_iterator()->get_name();
         const auto& str = name_node->get_name();
         local.empty()?
-            gen(op_loadg, global_find(str), name_node->get_line()):
-            gen(op_loadl, local_find(str), name_node->get_line());
+            gen(op_loadg, global_find(str), name_node->get_location()):
+            gen(op_loadl, local_find(str), name_node->get_location());
     } else { // use exist variable as the iterator
         mcall(node->get_iterator()->get_call());
         if (code.back().op==op_mcallg) {
@@ -772,17 +774,17 @@ void codegen::forei_gen(forei_expr* node) {
         } else if (code.back().op==op_mupval) {
             code.back().op=op_loadu;
         } else {
-            gen(op_meq, 1, node->get_iterator()->get_line());
+            gen(op_meq, 1, node->get_iterator()->get_location());
         }
     }
     ++in_loop_level.back();
     block_gen(node->get_code_block());
     --in_loop_level.back();
-    gen(op_jmp, ptr, node->get_line());
+    gen(op_jmp, ptr, node->get_location());
     code[ptr].num=code.size();
     load_continue_break(code.size()-1, code.size());
-    gen(op_pop, 0, node->get_value()->get_line());// pop vector
-    gen(op_pop, 0, node->get_line());// pop iterator
+    gen(op_pop, 0, node->get_value()->get_location());// pop vector
+    gen(op_pop, 0, node->get_location());// pop iterator
 }
 
 void codegen::statement_generation(expr* node) {
@@ -806,7 +808,7 @@ void codegen::statement_generation(expr* node) {
         case expr_type::ast_binary:
         case expr_type::ast_ternary:
             calc_gen(node);
-            gen(op_pop, 0, node->get_line());
+            gen(op_pop, 0, node->get_location());
             break;
         default: break;
     }
@@ -815,33 +817,33 @@ void codegen::statement_generation(expr* node) {
 void codegen::or_gen(binary_operator* node) {
     calc_gen(node->get_left());
     usize label_jump_true_1 = code.size();
-    gen(op_jt, 0, node->get_left()->get_line());
+    gen(op_jt, 0, node->get_left()->get_location());
 
-    gen(op_pop, 0, node->get_left()->get_line());
+    gen(op_pop, 0, node->get_left()->get_location());
     calc_gen(node->get_right());
     usize label_jump_true_2 = code.size();
-    gen(op_jt, 0, node->get_right()->get_line());
+    gen(op_jt, 0, node->get_right()->get_location());
 
-    gen(op_pop, 0, node->get_right()->get_line());
-    gen(op_pnil, 0, node->get_right()->get_line());
+    gen(op_pop, 0, node->get_right()->get_location());
+    gen(op_pnil, 0, node->get_right()->get_location());
 
     code[label_jump_true_1].num = code[label_jump_true_2].num = code.size();
 }
 
 void codegen::and_gen(binary_operator* node) {
     calc_gen(node->get_left());
-    gen(op_jt, code.size()+2, node->get_left()->get_line());
+    gen(op_jt, code.size()+2, node->get_left()->get_location());
 
     usize lable_jump_false = code.size();
-    gen(op_jmp, 0, node->get_left()->get_line());
-    gen(op_pop, 0, node->get_right()->get_line()); // jt jumps here
+    gen(op_jmp, 0, node->get_left()->get_location());
+    gen(op_pop, 0, node->get_right()->get_location()); // jt jumps here
 
     calc_gen(node->get_right());
-    gen(op_jt, code.size()+3, node->get_right()->get_line());
+    gen(op_jt, code.size()+3, node->get_right()->get_location());
 
     code[lable_jump_false].num = code.size();
-    gen(op_pop, 0, node->get_right()->get_line());
-    gen(op_pnil, 0, node->get_right()->get_line());
+    gen(op_pop, 0, node->get_right()->get_location());
+    gen(op_pnil, 0, node->get_right()->get_location());
     // jt jumps here, avoid pop and pnil
 }
 
@@ -849,11 +851,11 @@ void codegen::unary_gen(unary_operator* node) {
     calc_gen(node->get_value());
     switch(node->get_operator_type()) {
         case unary_operator::unary_type::negative:
-            gen(op_usub, 0, node->get_line()); break;
+            gen(op_usub, 0, node->get_location()); break;
         case unary_operator::unary_type::logical_not:
-            gen(op_lnot, 0, node->get_line()); break;
+            gen(op_lnot, 0, node->get_location()); break;
         case unary_operator::unary_type::bitwise_not:
-            gen(op_bnot, 0, node->get_line()); break;
+            gen(op_bnot, 0, node->get_location()); break;
     }
 }
 
@@ -877,27 +879,27 @@ void codegen::binary_gen(binary_operator* node) {
         case binary_operator::binary_type::cmpeq:
             calc_gen(node->get_left());
             calc_gen(node->get_right());
-            gen(op_eq, 0, node->get_line());
+            gen(op_eq, 0, node->get_location());
             return;
         case binary_operator::binary_type::cmpneq:
             calc_gen(node->get_left());
             calc_gen(node->get_right());
-            gen(op_neq, 0, node->get_line());
+            gen(op_neq, 0, node->get_location());
             return;
         case binary_operator::binary_type::bitwise_or:
             calc_gen(node->get_left());
             calc_gen(node->get_right());
-            gen(op_btor, 0, node->get_line());
+            gen(op_btor, 0, node->get_location());
             return;
         case binary_operator::binary_type::bitwise_xor:
             calc_gen(node->get_left());
             calc_gen(node->get_right());
-            gen(op_btxor, 0, node->get_line());
+            gen(op_btxor, 0, node->get_location());
             return;
         case binary_operator::binary_type::bitwise_and:
             calc_gen(node->get_left());
             calc_gen(node->get_right());
-            gen(op_btand, 0, node->get_line());
+            gen(op_btand, 0, node->get_location());
             return;
         default: break;
     }
@@ -906,99 +908,99 @@ void codegen::binary_gen(binary_operator* node) {
             calc_gen(node->get_left());
             if (node->get_right()->get_type()!=expr_type::ast_num) {
                 calc_gen(node->get_right());
-                gen(op_add, 0, node->get_line());
+                gen(op_add, 0, node->get_location());
             } else {
                 auto num = ((number_literal*)node->get_right())->get_number();
                 regist_num(num);
-                gen(op_addc, const_number_map.at(num), node->get_line());
+                gen(op_addc, const_number_map.at(num), node->get_location());
             }
             return;
         case binary_operator::binary_type::sub:
             calc_gen(node->get_left());
             if (node->get_right()->get_type()!=expr_type::ast_num) {
                 calc_gen(node->get_right());
-                gen(op_sub, 0, node->get_line());
+                gen(op_sub, 0, node->get_location());
             } else {
                 auto num = ((number_literal*)node->get_right())->get_number();
                 regist_num(num);
-                gen(op_subc, const_number_map.at(num), node->get_line());
+                gen(op_subc, const_number_map.at(num), node->get_location());
             }
             return;
         case binary_operator::binary_type::mult:
             calc_gen(node->get_left());
             if (node->get_right()->get_type()!=expr_type::ast_num) {
                 calc_gen(node->get_right());
-                gen(op_mul, 0, node->get_line());
+                gen(op_mul, 0, node->get_location());
             } else {
                 auto num = ((number_literal*)node->get_right())->get_number();
                 regist_num(num);
-                gen(op_mulc, const_number_map.at(num), node->get_line());
+                gen(op_mulc, const_number_map.at(num), node->get_location());
             }
             return;
         case binary_operator::binary_type::div:
             calc_gen(node->get_left());
             if (node->get_right()->get_type()!=expr_type::ast_num) {
                 calc_gen(node->get_right());
-                gen(op_div, 0, node->get_line());
+                gen(op_div, 0, node->get_location());
             } else {
                 auto num = ((number_literal*)node->get_right())->get_number();
                 regist_num(num);
-                gen(op_divc, const_number_map.at(num), node->get_line());
+                gen(op_divc, const_number_map.at(num), node->get_location());
             }
             return;
         case binary_operator::binary_type::concat:
             calc_gen(node->get_left());
             if (node->get_right()->get_type()!=expr_type::ast_str) {
                 calc_gen(node->get_right());
-                gen(op_lnk, 0, node->get_line());
+                gen(op_lnk, 0, node->get_location());
             } else {
                 const auto& str = ((string_literal*)node->get_right())->get_content();
                 regist_str(str);
-                gen(op_lnkc, const_string_map.at(str), node->get_line());
+                gen(op_lnkc, const_string_map.at(str), node->get_location());
             }
             break;
         case binary_operator::binary_type::less:
             calc_gen(node->get_left());
             if (node->get_right()->get_type()!=expr_type::ast_num) {
                 calc_gen(node->get_right());
-                gen(op_less, 0, node->get_line());
+                gen(op_less, 0, node->get_location());
             } else {
                 auto num = ((number_literal*)node->get_right())->get_number();
                 regist_num(num);
-                gen(op_lessc, const_number_map.at(num), node->get_line());
+                gen(op_lessc, const_number_map.at(num), node->get_location());
             }
             return;
         case binary_operator::binary_type::leq:
             calc_gen(node->get_left());
             if (node->get_right()->get_type()!=expr_type::ast_num) {
                 calc_gen(node->get_right());
-                gen(op_leq, 0, node->get_line());
+                gen(op_leq, 0, node->get_location());
             } else {
                 auto num = ((number_literal*)node->get_right())->get_number();
                 regist_num(num);
-                gen(op_leqc, const_number_map.at(num), node->get_line());
+                gen(op_leqc, const_number_map.at(num), node->get_location());
             }
             return;
         case binary_operator::binary_type::grt:
             calc_gen(node->get_left());
             if (node->get_right()->get_type()!=expr_type::ast_num) {
                 calc_gen(node->get_right());
-                gen(op_grt, 0, node->get_line());
+                gen(op_grt, 0, node->get_location());
             } else {
                 auto num = ((number_literal*)node->get_right())->get_number();
                 regist_num(num);
-                gen(op_grtc, const_number_map.at(num), node->get_line());
+                gen(op_grtc, const_number_map.at(num), node->get_location());
             }
             return;
         case binary_operator::binary_type::geq:
             calc_gen(node->get_left());
             if (node->get_right()->get_type()!=expr_type::ast_num) {
                 calc_gen(node->get_right());
-                gen(op_geq, 0, node->get_line());
+                gen(op_geq, 0, node->get_location());
             } else {
                 auto num = ((number_literal*)node->get_right())->get_number();
                 regist_num(num);
-                gen(op_geqc, const_number_map.at(num), node->get_line());
+                gen(op_geqc, const_number_map.at(num), node->get_location());
             }
             return;
         default: break;
@@ -1008,10 +1010,10 @@ void codegen::binary_gen(binary_operator* node) {
 void codegen::trino_gen(ternary_operator* node) {
     calc_gen(node->get_condition());
     usize label_jump_false = code.size();
-    gen(op_jf, 0, node->get_condition()->get_line());
+    gen(op_jf, 0, node->get_condition()->get_location());
     calc_gen(node->get_left());
     usize label_jump_to_exit = code.size();
-    gen(op_jmp, 0, node->get_left()->get_line());
+    gen(op_jmp, 0, node->get_left()->get_location());
     code[label_jump_false].num = code.size();
     calc_gen(node->get_right());
     code[label_jump_to_exit].num = code.size();
@@ -1020,7 +1022,7 @@ void codegen::trino_gen(ternary_operator* node) {
 void codegen::calc_gen(expr* node) {
     switch(node->get_type()) {
         case expr_type::ast_nil:
-            gen(op_pnil, 0, node->get_line()); break;
+            gen(op_pnil, 0, node->get_location()); break;
         case expr_type::ast_num:
             num_gen((number_literal*)node); break;
         case expr_type::ast_str:
@@ -1064,18 +1066,15 @@ void codegen::block_gen(code_block* node) {
             case expr_type::ast_num:
             case expr_type::ast_str:
             case expr_type::ast_bool: break;
-            case expr_type::ast_file_info:
-                // special node type in main block
-                fileindex = ((file_info*)tmp)->get_index(); break;
             case expr_type::ast_cond:
                 cond_gen((condition_expr*)tmp); break;
             case expr_type::ast_continue:
                 continue_ptr.front().push_back(code.size());
-                gen(op_jmp, 0, tmp->get_line());
+                gen(op_jmp, 0, tmp->get_location());
                 break;
             case expr_type::ast_break:
                 break_ptr.front().push_back(code.size());
-                gen(op_jmp, 0, tmp->get_line());
+                gen(op_jmp, 0, tmp->get_location());
                 break;
             case expr_type::ast_while:
             case expr_type::ast_for:
@@ -1101,16 +1100,20 @@ void codegen::block_gen(code_block* node) {
 
 void codegen::ret_gen(return_expr* node) {
     for(u32 i = 0; i<in_loop_level.back(); ++i) {
-        gen(op_pop, 0, node->get_line());
-        gen(op_pop, 0, node->get_line());
+        gen(op_pop, 0, node->get_location());
+        gen(op_pop, 0, node->get_location());
     }
     calc_gen(node->get_value());
-    gen(op_ret, 0, node->get_line());
+    gen(op_ret, 0, node->get_location());
 }
 
 const error& codegen::compile(parse& parse, linker& import) {
-    fileindex = 0;
-    file = import.filelist();
+    const auto& file = import.filelist();
+    file_map = {};
+    for(usize i = 0; i<file.size(); ++i) {
+        file_map[file[i]] = i;
+    }
+
     in_loop_level.push_back(0);
 
     // add special symbol globals, which is a hash stores all global variables
@@ -1119,9 +1122,9 @@ const error& codegen::compile(parse& parse, linker& import) {
     add_symbol("arg");
 
     find_symbol(parse.tree()); // search symbols first
-    gen(op_intg, global.size(), 0);
+    gen(op_intg, global.size(), parse.tree()->get_location());
     block_gen(parse.tree()); // generate main block
-    gen(op_exit, 0, 0);
+    gen(op_exit, 0, parse.tree()->get_location());
 
     // size out of bound check
     if (const_number_table.size()>0xffffff) {
diff --git a/src/nasal_codegen.h b/src/nasal_codegen.h
index 884bd64..dc8a683 100644
--- a/src/nasal_codegen.h
+++ b/src/nasal_codegen.h
@@ -22,15 +22,24 @@
 
 class codegen {
 private:
-    u16 fileindex;
     error err;
-    std::vector<std::string> file;
+
+    // file mapper for file -> index
+    std::unordered_map<std::string, usize> file_map;
+
+    // used for generate pop in return expression
     std::vector<u32> in_loop_level;
+
+    // constant numbers and strings
     std::unordered_map<f64, u32> const_number_map;
     std::unordered_map<std::string, u32> const_string_map;
     std::vector<f64> const_number_table;
     std::vector<std::string> const_string_table;
+
+    // generated opcodes
     std::vector<opcode> code;
+
+    // used to store jmp operands index, to fill the jump address back
     std::list<std::vector<i32>> continue_ptr;
     std::list<std::vector<i32>> break_ptr;
 
@@ -38,6 +47,7 @@ private:
     // global : max STACK_DEPTH-1 values
     std::unordered_map<std::string, i32> global;
     std::unordered_map<std::string, std::unordered_set<std::string>> experimental_namespace;
+
     // local  : max 32768 upvalues 65536 values
     // but in fact local scope also has less than STACK_DEPTH value
     std::list<std::unordered_map<std::string, i32>> local;
@@ -56,7 +66,7 @@ private:
     i32 global_find(const std::string&);
     i32 upvalue_find(const std::string&);
 
-    void gen(u8, u32, u32);
+    void gen(u8, u32, const span&);
 
     void num_gen(number_literal*);
     void str_gen(string_literal*);
@@ -105,7 +115,7 @@ public:
     }
 
 public:
-    codegen(): fileindex(0) {}
+    codegen() = default;
     const error& compile(parse&, linker&);
     void print(std::ostream&);
     void symbol_dump(std::ostream&) const;
diff --git a/src/nasal_import.cpp b/src/nasal_import.cpp
index d79ac30..af2e7f0 100644
--- a/src/nasal_import.cpp
+++ b/src/nasal_import.cpp
@@ -313,12 +313,15 @@ definition_expr* linker::generate_module_definition(code_block* block) {
 
 code_block* linker::load(code_block* root, u16 fileindex) {
     auto tree = new code_block({0, 0, 0, 0, files[fileindex]});
+    // load library, this ast will be linked with root directly
+    // so no namespace is generated
     if (!lib_loaded) {
         auto tmp = import_nasal_lib();
         link(tree, tmp);
         delete tmp;
         lib_loaded = true;
     }
+    // load imported modules
     for(auto i : root->get_expressions()) {
         if (!import_check(i)) {
             break;
@@ -327,9 +330,6 @@ code_block* linker::load(code_block* root, u16 fileindex) {
         tree->add_expression(generate_module_definition(tmp));
     }
     // add root to the back of tree
-    auto file_head = new file_info(
-        {0, 0, 0, 0, files[fileindex]}, fileindex, files[fileindex]);
-    tree->add_expression(file_head);
     link(tree, root);
     return tree;
 }
diff --git a/std/fg_env.nas b/std/fg_env.nas
index c8168d0..47d435d 100644
--- a/std/fg_env.nas
+++ b/std/fg_env.nas
@@ -1,5 +1,6 @@
 # flightgear developer environments simulator (beta)
 # ValKmjolnir 2022
+import.std.runtime;
 
 println("-------------------------------------------------------------");
 println(" FlightGear simulated-env for developers project, since 2019");
diff --git a/std/io.nas b/std/io.nas
new file mode 100644
index 0000000..cfca4ad
--- /dev/null
+++ b/std/io.nas
@@ -0,0 +1,68 @@
+# io.nas
+# 2023 by ValKmjolnir
+
+var SEEK_SET = 0;
+var SEEK_CUR = 1;
+var SEEK_END = 2;
+
+# get content of a file by filename. returns a string.
+var readfile = func(filename) {
+    return __readfile(filename);
+}
+
+# input a string as the content of a file.
+var fout = func(filename, str) {
+    return __fout(filename, str);
+}
+
+# use C access
+var exists = func(filename) {
+    return __exists(filename);
+}
+
+# same as C fopen. open file and get the FILE*.
+var open = func(filename, mode = "r") {
+    return __open(filename, mode);
+}
+
+# same as C fclose. close file by FILE*.
+var close = func(filehandle) {
+    return __close(filehandle);
+}
+
+# same as C fread. read file by FILE*.
+# caution: buf must be a mutable string.use mut("") to get an empty mutable string.
+var read = func(filehandle, buf, len) {
+    return __read(filehandle, buf, len);
+}
+
+# same as C fwrite. write file by FILE*.
+var write = func(filehandle, str) {
+    return __write(filehandle, str);
+}
+
+# same as C fseek. seek place by FILE*.
+var seek = func(filehandle, pos, whence) {
+    return __seek(filehandle, pos, whence);
+}
+
+# same as C ftell.
+var tell = func(filehandle) {
+    return __tell(filehandle);
+}
+
+# read file by lines. use FILE*.
+# get nil if EOF
+var readln = func(filehandle) {
+    return __readln(filehandle);
+}
+
+# same as C stat.
+var stat = func(filename) {
+    return __stat(filename);
+}
+
+# same as C feof. check if FILE* gets the end of file(EOF).
+var eof = func(filehandle) {
+    return __eof(filehandle);
+}
diff --git a/std/lib.nas b/std/lib.nas
index 6e513fc..c90bd77 100644
--- a/std/lib.nas
+++ b/std/lib.nas
@@ -2,6 +2,10 @@
 # 2019 ValKmjolnir
 
 import.std.coroutine;
+import.std.math;
+import.std.string;
+import.std.io;
+import.std.os;
 
 # print is used to print all things in nasal, try and see how it works.
 # this function uses std::cout to output logs.
@@ -327,38 +331,6 @@ var md5 = func(str) {
     return __md5(str);
 }
 
-var io = {
-    SEEK_SET: 0,
-    SEEK_CUR: 1,
-    SEEK_END: 2,
-    # get content of a file by filename. returns a string.
-    readfile: func(filename) {return __readfile(filename);},
-    # input a string as the content of a file.
-    fout: func(filename, str) {return __fout(filename, str);},
-    # use C access
-    exists:func(filename) {return __exists(filename);},
-    # same as C fopen. open file and get the FILE*.
-    open: func(filename, mode = "r") {return __open(filename, mode);},
-    # same as C fclose. close file by FILE*.
-    close: func(filehandle) {return __close(filehandle);},
-    # same as C fread. read file by FILE*.
-    # caution: buf must be a mutable string.use mut("") to get an empty mutable string.
-    read: func(filehandle, buf, len) {return __read(filehandle, buf, len);},
-    # same as C fwrite. write file by FILE*.
-    write: func(filehandle, str) {return __write(filehandle, str);},
-    # same as C fseek. seek place by FILE*.
-    seek: func(filehandle, pos, whence) {return __seek(filehandle, pos, whence);},
-    # same as C ftell.
-    tell: func(filehandle) {return __tell(filehandle);},
-    # read file by lines. use FILE*.
-    # get nil if EOF
-    readln: func(filehandle) {return __readln(filehandle);},
-    # same as C stat.
-    stat: func(filename) {return __stat(filename);},
-    # same as C feof. check if FILE* gets the end of file(EOF).
-    eof: func(filehandle) {return __eof(filehandle);}
-};
-
 # get file status. using data from io.stat
 var fstat = func(filename) {
     var s = io.stat(filename);
@@ -412,28 +384,6 @@ var bits = {
     buf: func(len) {return __buf;}
 };
 
-# mostly used math functions and special constants, you know.
-var math = {
-    e: 2.7182818284590452354,
-    pi: 3.14159265358979323846264338327950288,
-    inf: 1/0,
-    nan: 0/0,
-    abs: func(x) {return x>0? x:-x;},
-    floor: func(x) {return __floor(x);},
-    pow: func(x, y) {return __pow(x, y);},
-    sin: func(x) {return __sin(x);},
-    cos: func(x) {return __cos(x);},
-    tan: func(x) {return __tan(x);},
-    exp: func(x) {return __exp(x);},
-    lg: func(x) {return __lg(x);},
-    ln: func(x) {return __ln(x);},
-    sqrt: func(x) {return __sqrt(x);},
-    atan2: func(x, y) {return __atan2(x, y);},
-    isnan: func(x) {return __isnan(x);},
-    max: func(x, y) {return x>y? x:y;},
-    min: func(x, y) {return x<y? x:y;}
-};
-
 # important global constants
 var D2R = math.pi / 180;               # degree to radian
 var R2D = 180 / math.pi;               # radian to degree
@@ -520,25 +470,6 @@ var dylib = {
     }
 };
 
-# os is used to use or get some os-related info/functions.
-# windows/macOS/linux are supported.
-var os = {
-    # get a string that tell which os it runs on.
-    platform: func() {return __platform;},
-    time: func() {return __logtime;},
-    arch: func() {return __arch;}
-};
-
-# runtime gives us some functions that we could manage it manually.
-var runtime = {
-    # command line arguments
-    argv: func() {return globals.arg;},
-    gc: {
-        extend: func(type) {return __gcextd;},
-        info: func() {return __gcinfo;}
-    }
-};
-
 # functions that not supported in this runtime:
 var bind = func(function, locals, outer_scope = nil) {
     die("this runtime does not support bind");
diff --git a/std/list.nas b/std/list.nas
index 6b7d669..2b70bd7 100644
--- a/std/list.nas
+++ b/std/list.nas
@@ -1,51 +1,77 @@
 # list.nas
 # valkmjolnir 2021/3/31
-var list=func(){
-    var (begin,end)=(nil,nil);
-    return{
-        push_back:func(elem){
-            var tmp={elem:elem,prev:nil,next:nil};
-            if(end!=nil){
-                end.next=tmp;
-                tmp.prev=end;
-                end=tmp;
+
+var new = func() {
+    var (begin, end, len) = (nil, nil, 0);
+    return {
+        push_back: func(elem) {
+            var tmp = {
+                elem: elem,
+                prev: nil,
+                next: nil
+            };
+            if(end!=nil) {
+                end.next = tmp;
+                tmp.prev = end;
+                end = tmp;
+            } else {
+                begin = end = tmp;
             }
-            else
-                begin=end=tmp;
+            len += 1;
         },
-        push_front:func(elem){
-            var tmp={elem:elem,prev:nil,next:nil};
-            if(begin!=nil){
-                begin.prev=tmp;
-                tmp.next=begin;
-                begin=tmp;
+        push_front: func(elem) {
+            var tmp = {
+                elem: elem,
+                prev: nil,
+                next: nil
+            };
+            if (begin!=nil) {
+                begin.prev = tmp;
+                tmp.next = begin;
+                begin = tmp;
+            } else {
+                begin = end = tmp;
             }
-            else
-                begin=end=tmp;
+            len += 1;
         },
-        pop_back:func(){
-            if(end!=nil)
-                end=end.prev;
-            if(end==nil)
-                begin=nil;
-            else
-                end.next=nil;
+        pop_back: func() {
+            if (end!=nil) {
+                end = end.prev;
+            }
+            if (end==nil) {
+                begin = nil;
+            } else {
+                end.next = nil;
+            }
+            if (len) {
+                len -= 1;
+            }
         },
-        pop_front:func(){
-            if(begin!=nil)
-                begin=begin.next;
-            if(begin==nil)
-                end=nil;
-            else
-                begin.prev=nil;
+        pop_front: func() {
+            if (begin!=nil) {
+                begin = begin.next;
+            }
+            if (begin==nil) {
+                end = nil;
+            } else {
+                begin.prev = nil;
+            }
+            if (len) {
+                len -= 1;
+            }
         },
-        front:func(){
-            if(begin!=nil)
+        front: func() {
+            if (begin!=nil) {
                 return begin.elem;
+            }
         },
-        back:func(){
-            if(end!=nil)
+        back: func() {
+            if (end!=nil) {
                 return end.elem;
+            }
         },
+        length: func() {
+            return len;
+        }
     };
 }
\ No newline at end of file
diff --git a/std/math.nas b/std/math.nas
new file mode 100644
index 0000000..b3c7e1d
--- /dev/null
+++ b/std/math.nas
@@ -0,0 +1,65 @@
+# math.nas
+# 2023 by ValKmjolnir
+# mostly used math functions and special constants, you know.
+
+var e = 2.7182818284590452354;
+var pi = 3.14159265358979323846264338327950288;
+
+var inf = 1/0;
+var nan = 0/0;
+
+var abs = func(x) {
+    return x>0? x:-x;
+}
+
+var floor = func(x) {
+    return __floor(x);
+}
+
+var pow = func(x, y) {
+    return __pow(x, y);
+}
+
+var sin = func(x) {
+    return __sin(x);
+}
+
+var cos = func(x) {
+    return __cos(x);
+}
+
+var tan = func(x) {
+    return __tan(x);
+}
+
+var exp = func(x) {
+    return __exp(x);
+}
+
+var lg = func(x) {
+    return __lg(x);
+}
+
+var ln = func(x) {
+    return __ln(x);
+}
+
+var sqrt = func(x) {
+    return __sqrt(x);
+}
+
+var atan2 = func(x, y) {
+    return __atan2(x, y);
+}
+
+var isnan = func(x) {
+    return __isnan(x);
+}
+
+var max = func(x, y) {
+    return x>y? x:y;
+}
+
+var min = func(x, y) {
+    return x<y? x:y;
+}
diff --git a/std/os.nas b/std/os.nas
new file mode 100644
index 0000000..4f95700
--- /dev/null
+++ b/std/os.nas
@@ -0,0 +1,18 @@
+# os.nas
+# 2023 by ValKmjolnir
+
+# os is used to use or get some os-related info/functions.
+# windows/macOS/linux are supported.
+
+# get a string that tell which os it runs on.
+var platform = func() {
+    return __platform;
+}
+
+var time = func() {
+    return __logtime;
+}
+
+var arch = func() {
+    return __arch;
+}
diff --git a/std/runtime.nas b/std/runtime.nas
new file mode 100644
index 0000000..b6edeaf
--- /dev/null
+++ b/std/runtime.nas
@@ -0,0 +1,13 @@
+# runtime.nas
+# 2023 by ValKmjolnir
+# runtime gives us some functions that we could manage it manually.
+
+# command line arguments
+var argv = func() {
+    return globals.arg;
+}
+
+var gc = {
+    extend: func(type) {return __gcextd;},
+    info: func() {return __gcinfo;}
+};
diff --git a/std/string.nas b/std/string.nas
index f1c1e46..5aefb90 100644
--- a/std/string.nas
+++ b/std/string.nas
@@ -1,9 +1,12 @@
 # string.nas
 # ValKmjolnir 2022/10/5
 
-var join=func(vec){
-    var res="";
-    foreach(var i;vec)
-        res~=i;
+var join=func(sep, vec){
+    var len = size(vec);
+    var res = "";
+    for(var i = 0; i<len; i+=1) {
+        res ~= vec[i];
+        res ~= (i==len-1? "":sep);
+    }
     return res;
 }
\ No newline at end of file
diff --git a/test/console3D.nas b/test/console3D.nas
index ff8f794..ccc3332 100644
--- a/test/console3D.nas
+++ b/test/console3D.nas
@@ -22,6 +22,7 @@
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 # SOFTWARE.
 import.module.libmat;
+import.std.runtime;
 
 func(){
     # allocate more spaces
diff --git a/test/donuts.nas b/test/donuts.nas
index ba6a15a..6f38fdf 100644
--- a/test/donuts.nas
+++ b/test/donuts.nas
@@ -1,3 +1,5 @@
+import.std.runtime;
+
 var mod=func(n,a){
     return n-int(n/a)*a;
 }
diff --git a/test/gc_test.nas b/test/gc_test.nas
index 2aa9d04..b7e223c 100644
--- a/test/gc_test.nas
+++ b/test/gc_test.nas
@@ -1,3 +1,4 @@
+import.std.runtime;
 
 var test_func = func(test_processes...) {
     var test_process_total = maketimestamp();
diff --git a/test/hexdump.nas b/test/hexdump.nas
index fd3cd49..dcfaafc 100644
--- a/test/hexdump.nas
+++ b/test/hexdump.nas
@@ -1,6 +1,7 @@
 # hexdump.nas by ValKmjolnir
 # 2021/8/13
 import.std.file;
+import.std.runtime;
 
 # init
 var hex=func(){
diff --git a/test/jsonrpc.nas b/test/jsonrpc.nas
index f3e78f9..2b207dc 100644
--- a/test/jsonrpc.nas
+++ b/test/jsonrpc.nas
@@ -1,5 +1,6 @@
 import.module.libsock;
 import.std.json;
+import.std.runtime;
 
 var JSON = json.JSON;
 var socket = libsock.socket;
diff --git a/test/life.nas b/test/life.nas
index 3978352..9e29298 100644
--- a/test/life.nas
+++ b/test/life.nas
@@ -1,4 +1,5 @@
 import.std.process_bar;
+import.std.runtime;
 
 var new_map=func(width,height){
     var tmp=[];
diff --git a/test/occupation.nas b/test/occupation.nas
index b46fe76..9ea4302 100644
--- a/test/occupation.nas
+++ b/test/occupation.nas
@@ -1,5 +1,6 @@
 import.std.process_bar;
 import.module.libkey;
+import.std.runtime;
 
 var is_windows_platform=os.platform()=="windows";
 var is_macos_platform=os.platform()=="macOS";
diff --git a/test/scalar.nas b/test/scalar.nas
index 160ac38..eb0b0ea 100644
--- a/test/scalar.nas
+++ b/test/scalar.nas
@@ -1,3 +1,5 @@
+import.std.runtime;
+
 # basic type
 nil;
 2147483647;
@@ -202,6 +204,7 @@ foreach(i;a){
     ;
 }
 println(runtime.argv());
+println(globals.arg);
 func(a,b,c,d="只有红茶可以吗"){
     println(a,' ',b,' ',c,' ',d,' true: ',true,' false: ',false);
 }(c:1919810,b:514,a:114);
diff --git a/test/snake.nas b/test/snake.nas
index cad86a6..08b82a9 100644
--- a/test/snake.nas
+++ b/test/snake.nas
@@ -1,71 +1,6 @@
 import.module.libkey;
-
-var list=func(){
-    var (begin,end,len)=(nil,nil,0);
-    return{
-        push_back:func(elem){
-            var tmp={
-                elem:elem,
-                prev:nil,
-                next:nil
-            };
-            if(end!=nil){
-                end.next=tmp;
-                tmp.prev=end;
-                end=tmp;
-            }else{
-                begin=end=tmp;
-            }
-            len+=1;
-        },
-        push_front:func(elem){
-            var tmp={
-                elem:elem,
-                prev:nil,
-                next:nil
-            };
-            if(begin!=nil){
-                begin.prev=tmp;
-                tmp.next=begin;
-                begin=tmp;
-            }else{
-                begin=end=tmp;
-            }
-            len+=1;
-        },
-        pop_back:func(){
-            if(end!=nil)
-                end=end.prev;
-            if(end==nil)
-                begin=nil;
-            else
-                end.next=nil;
-            if(len)
-                len-=1;
-        },
-        pop_front:func(){
-            if(begin!=nil)
-                begin=begin.next;
-            if(begin==nil)
-                end=nil;
-            else
-                begin.prev=nil;
-            if(len)
-                len-=1;
-        },
-        front:func(){
-            if(begin!=nil)
-                return begin.elem;
-        },
-        back:func(){
-            if(end!=nil)
-                return end.elem;
-        },
-        length:func(){
-            return len;
-        }
-    };
-}
+import.std.list;
+import.std.runtime;
 
 var game=func(x,y){
     rand(time(0));
@@ -88,7 +23,7 @@ var game=func(x,y){
             vec[i][j]=0;
     }
 
-    var snake=list();
+    var snake = list.new();
     snake.push_back([int(x/2),int(y/3)]);
     snake.push_back([int(x/2),int(y/3)+1]);
     vec[int(x/2)][int(y/3)]=1;
diff --git a/test/tetris.nas b/test/tetris.nas
index 547d2f6..e2e1cf4 100644
--- a/test/tetris.nas
+++ b/test/tetris.nas
@@ -1,4 +1,6 @@
 import.module.libkey;
+import.std.runtime;
+
 var color=[
     "\e[31m","\e[32m","\e[33m","\e[34m","\e[35m","\e[36m",
     "\e[91m","\e[92m","\e[93m","\e[94m","\e[95m","\e[96m",
diff --git a/test/watchdog.nas b/test/watchdog.nas
index cb67687..a27813c 100644
--- a/test/watchdog.nas
+++ b/test/watchdog.nas
@@ -1,3 +1,5 @@
+import.std.runtime;
+
 var os_time=func(){
     return "[\e[33;1m"~os.time()~"\e[0m] ";
 }
diff --git a/test/word_collector.nas b/test/word_collector.nas
index 9e801cc..87e7151 100644
--- a/test/word_collector.nas
+++ b/test/word_collector.nas
@@ -1,3 +1,4 @@
+import.std.runtime;
 
 var to_lower=func(s){
     var tmp="";