diff --git a/README.md b/README.md
index 9ca6eda..81dae69 100644
--- a/README.md
+++ b/README.md
@@ -763,7 +763,7 @@ extern "C" nasal_ref fib(std::vector<nasal_ref>& args,nasal_gc& gc){
     // ok, you must know that vm_num now is not managed by gc
     // if want to return a gc object, use gc.alloc(type)
     // usage of gc is the same as adding a native function
-    return {vm_num,fibonaci(num.to_number())};
+    return {vm_num,fibonaci(num.tonum())};
 }
 ```
 
diff --git a/doc/README_zh.md b/doc/README_zh.md
index 593ae81..f79f746 100644
--- a/doc/README_zh.md
+++ b/doc/README_zh.md
@@ -717,7 +717,7 @@ extern "C" nasal_ref fib(std::vector<nasal_ref>& args,nasal_gc& gc){
         return builtin_err("extern_fib","\"num\" must be number");
     // vm_num作为普通的数字类型，不是内存管理的对象，所以无需申请
     // 如果需要返回内存管理的对象，请使用gc.alloc(type)
-    return {vm_num,fibonaci(num.to_number())};
+    return {vm_num,fibonaci(num.tonum())};
 }
 ```
 
diff --git a/module/fib.cpp b/module/fib.cpp
index a3e2b53..71eb3bc 100644
--- a/module/fib.cpp
+++ b/module/fib.cpp
@@ -13,7 +13,7 @@ extern "C" nasal_ref fib(std::vector<nasal_ref>& args,nasal_gc& gc){
     nasal_ref num=args[0];
     if(num.type!=vm_num)
         return builtin_err("extern_fib","\"num\" must be number");
-    return {vm_num,fibonaci(num.to_number())};
+    return {vm_num,fibonaci(num.tonum())};
 }
 extern "C" nasal_ref quick_fib(std::vector<nasal_ref>& args,nasal_gc& gc){
     std::cout<<"[mod] this is the first test module of nasal\n";
diff --git a/nasal_builtin.h b/nasal_builtin.h
index 778b916..4340462 100644
--- a/nasal_builtin.h
+++ b/nasal_builtin.h
@@ -430,7 +430,7 @@ nasal_ref builtin_num(nasal_ref* local,nasal_gc& gc)
         return val;
     if(val.type!=vm_str)
         return nil;
-    double res=val.to_number();
+    double res=val.tonum();
     if(std::isnan(res))
         return nil;
     return {vm_num,res};
@@ -1418,7 +1418,7 @@ nasal_ref builtin_coresume(nasal_ref* local,nasal_gc& gc)
 nasal_ref builtin_coyield(nasal_ref* local,nasal_gc& gc)
 {
     if(!gc.coroutine)
-        return builtin_err("coroutine::yield","cannot yield, no coroutine is running");
+        return builtin_err("coroutine::yield","no coroutine is running");
     gc.ctxreserve();
     // this will set to main stack top
     // then builtin_coresume will return it
diff --git a/nasal_gc.h b/nasal_gc.h
index 0eed8a1..63a8025 100644
--- a/nasal_gc.h
+++ b/nasal_gc.h
@@ -85,8 +85,8 @@ struct nasal_ref
     bool operator==(const nasal_ref& nr){return type==nr.type && value.gcobj==nr.value.gcobj;}
     bool operator!=(const nasal_ref& nr){return type!=nr.type || value.gcobj!=nr.value.gcobj;}
     // number and string can be translated to each other
-    double      to_number();
-    std::string to_string();
+    double      tonum();
+    std::string tostr();
     void        print();
     bool        objchk(uint32_t);
     inline nasal_ref*   addr();
@@ -380,11 +380,11 @@ nasal_val::~nasal_val()
     }
     type=vm_nil;
 }
-double nasal_ref::to_number()
+double nasal_ref::tonum()
 {
     return type!=vm_str?value.num:str2num(str().c_str());
 }
-std::string nasal_ref::to_string()
+std::string nasal_ref::tostr()
 {
     if(type==vm_str)
         return str();
diff --git a/nasal_vm.h b/nasal_vm.h
index 5f1ab3f..9d3f8fd 100644
--- a/nasal_vm.h
+++ b/nasal_vm.h
@@ -513,11 +513,11 @@ inline void nasal_vm::opr_unot()
 }
 inline void nasal_vm::opr_usub()
 {
-    top[0]={vm_num,-top[0].to_number()};
+    top[0]={vm_num,-top[0].tonum()};
 }
 
 #define op_calc(type)\
-    nasal_ref val(vm_num,top[-1].to_number() type top[0].to_number());\
+    nasal_ref val(vm_num,top[-1].tonum() type top[0].tonum());\
     (--top)[0]=val;
 
 inline void nasal_vm::opr_add(){op_calc(+);}
@@ -527,12 +527,12 @@ inline void nasal_vm::opr_div(){op_calc(/);}
 inline void nasal_vm::opr_lnk()
 {
     nasal_ref val=gc.alloc(vm_str);
-    val.str()=top[-1].to_string()+top[0].to_string();
+    val.str()=top[-1].tostr()+top[0].tostr();
     (--top)[0]=val;
 }
 
 #define op_calc_const(type)\
-    nasal_ref val(vm_num,top[0].to_number() type num_table[imm[pc]]);\
+    nasal_ref val(vm_num,top[0].tonum() type num_table[imm[pc]]);\
     top[0]=val;
 
 inline void nasal_vm::opr_addc(){op_calc_const(+);}
@@ -542,12 +542,12 @@ inline void nasal_vm::opr_divc(){op_calc_const(/);}
 inline void nasal_vm::opr_lnkc()
 {
     nasal_ref val=gc.alloc(vm_str);
-    val.str()=top[0].to_string()+str_table[imm[pc]];
+    val.str()=top[0].tostr()+str_table[imm[pc]];
     top[0]=val;
 }
 
 #define op_calc_eq(type)\
-    nasal_ref val(vm_num,memr[0].to_number() type top[-1].to_number());\
+    nasal_ref val(vm_num,memr[0].tonum() type top[-1].tonum());\
     (--top)[0]=memr[0]=val;\
     memr=nullptr;\
     top-=imm[pc];
@@ -559,14 +559,14 @@ inline void nasal_vm::opr_diveq(){op_calc_eq(/);}
 inline void nasal_vm::opr_lnkeq()
 {
     nasal_ref val=gc.alloc(vm_str);
-    val.str()=memr[0].to_string()+top[-1].to_string();
+    val.str()=memr[0].tostr()+top[-1].tostr();
     (--top)[0]=memr[0]=val;
     memr=nullptr;
     top-=imm[pc];
 }
 
 #define op_calc_eq_const(type)\
-    nasal_ref val(vm_num,memr[0].to_number() type num_table[imm[pc]&0x7fffffff]);\
+    nasal_ref val(vm_num,memr[0].tonum() type num_table[imm[pc]&0x7fffffff]);\
     top[0]=memr[0]=val;\
     memr=nullptr;\
     top-=(imm[pc]>>31);
@@ -578,7 +578,7 @@ inline void nasal_vm::opr_diveqc(){op_calc_eq_const(/);}
 inline void nasal_vm::opr_lnkeqc()
 {
     nasal_ref val=gc.alloc(vm_str);
-    val.str()=memr[0].to_string()+str_table[imm[pc]&0x7fffffff];
+    val.str()=memr[0].tostr()+str_table[imm[pc]&0x7fffffff];
     top[0]=memr[0]=val;
     memr=nullptr;
     top-=(imm[pc]>>31);
@@ -605,7 +605,7 @@ inline void nasal_vm::opr_eq()
         top[0]=(val1.str()==val2.str())?one:zero;
     else if((val1.type==vm_num || val2.type==vm_num)
         && val1.type!=vm_nil && val2.type!=vm_nil)
-        top[0]=(val1.to_number()==val2.to_number())?one:zero;
+        top[0]=(val1.tonum()==val2.tonum())?one:zero;
     else
         top[0]=(val1==val2)?one:zero;
 }
@@ -619,14 +619,14 @@ inline void nasal_vm::opr_neq()
         top[0]=(val1.str()!=val2.str())?one:zero;
     else if((val1.type==vm_num || val2.type==vm_num)
         && val1.type!=vm_nil && val2.type!=vm_nil)
-        top[0]=(val1.to_number()!=val2.to_number())?one:zero;
+        top[0]=(val1.tonum()!=val2.tonum())?one:zero;
     else
         top[0]=(val1!=val2)?one:zero;
 }
 
 #define op_cmp(type)\
     --top;\
-    top[0]=(top[0].to_number() type top[1].to_number())?one:zero;
+    top[0]=(top[0].tonum() type top[1].tonum())?one:zero;
 
 inline void nasal_vm::opr_less(){op_cmp(<);}
 inline void nasal_vm::opr_leq(){op_cmp(<=);}
@@ -634,7 +634,7 @@ inline void nasal_vm::opr_grt(){op_cmp(>);}
 inline void nasal_vm::opr_geq(){op_cmp(>=);}
 
 #define op_cmp_const(type)\
-    top[0]=(top[0].to_number() type num_table[imm[pc]])?one:zero;
+    top[0]=(top[0].tonum() type num_table[imm[pc]])?one:zero;
 
 inline void nasal_vm::opr_lessc(){op_cmp_const(<);}
 inline void nasal_vm::opr_leqc(){op_cmp_const(<=);}
@@ -705,9 +705,9 @@ inline void nasal_vm::opr_callv()
     nasal_ref vec=(--top)[0];
     if(vec.type==vm_vec)
     {
-        top[0]=vec.vec().get_val(val.to_number());
+        top[0]=vec.vec().get_val(val.tonum());
         if(top[0].type==vm_none)
-            die("callv: index out of range:"+std::to_string(val.to_number()));
+            die("callv: index out of range:"+std::to_string(val.tonum()));
     }
     else if(vec.type==vm_hash)
     {
@@ -722,10 +722,10 @@ inline void nasal_vm::opr_callv()
     else if(vec.type==vm_str)
     {
         std::string& str=vec.str();
-        int num=val.to_number();
+        int num=val.tonum();
         int str_size=str.length();
         if(num<-str_size || num>=str_size)
-            die("callv: index out of range:"+std::to_string(val.to_number()));
+            die("callv: index out of range:"+std::to_string(val.tonum()));
         top[0]={vm_num,double((uint8_t)str[num>=0? num:num+str_size])};
     }
     else
@@ -862,9 +862,9 @@ inline void nasal_vm::opr_slcend()
 inline void nasal_vm::opr_slc()
 {
     nasal_ref val=(top--)[0];
-    nasal_ref res=top[-1].vec().get_val(val.to_number());
+    nasal_ref res=top[-1].vec().get_val(val.tonum());
     if(res.type==vm_none)
-        die("slc: index out of range:"+std::to_string(val.to_number()));
+        die("slc: index out of range:"+std::to_string(val.tonum()));
     top[0].vec().elems.push_back(res);
 }
 inline void nasal_vm::opr_slc2()
@@ -875,8 +875,8 @@ inline void nasal_vm::opr_slc2()
     std::vector<nasal_ref>& aim=top[0].vec().elems;
 
     uint8_t type1=val1.type,type2=val2.type;
-    int num1=val1.to_number();
-    int num2=val2.to_number();
+    int num1=val1.tonum();
+    int num2=val2.tonum();
     int size=ref.size();
     if(type1==vm_nil && type2==vm_nil)
     {
@@ -925,9 +925,9 @@ inline void nasal_vm::opr_mcallv()
     nasal_ref vec=(--top)[0]; // mcall vector, reserved on stack to avoid gc
     if(vec.type==vm_vec)
     {
-        memr=vec.vec().get_mem(val.to_number());
+        memr=vec.vec().get_mem(val.tonum());
         if(!memr)
-            die("mcallv: index out of range:"+std::to_string(val.to_number()));
+            die("mcallv: index out of range:"+std::to_string(val.tonum()));
     }
     else if(vec.type==vm_hash) // special call of hash, this do mcallh but use the mcallv way
     {
diff --git a/test/coroutine.nas b/test/coroutine.nas
index 0858604..3db0181 100644
--- a/test/coroutine.nas
+++ b/test/coroutine.nas
@@ -1,5 +1,6 @@
 # coroutine.nas by ValKmjolnir
 # 2022/5/19
+import("stl/process_bar.nas");
 var fib=func(){
     var (a,b)=(1,1);
     coroutine.yield(a);
@@ -10,41 +11,46 @@ var fib=func(){
     }
     return;
 }
-
+# different coroutines don't share the same local scope
 var co=[coroutine.create(fib),coroutine.create(fib)];
 for(var i=0;i<45;i+=1){
     var res=[coroutine.resume(co[0]),coroutine.resume(co[1])];
-    println('coroutine[0]:',res[0]==nil?nil:res[0][0],'\ncoroutine[1]:',res[1]==nil?nil:res[1][0]);
+    println('co[0]: ',res[0]==nil?nil:res[0][0],'\nco[1]: ',res[1]==nil?nil:res[1][0]);
 }
 
-var productor=func(){
-    for(var i=0;;i+=1)
-        coroutine.yield(i);
-}
-var counter=0;
-var consumer=func(){
-    counter+=1;
-    print('[',counter,']: ');
-    for(var i=0;i<5;i+=1){
-        print('[',i,']',coroutine.resume(co)[0],' ');
-    }
-    print('\n');
-}
-
-var co=coroutine.create(productor);
-var tm=maketimestamp();
-tm.stamp();
-while(tm.elapsedMSec()<1000)
-    consumer();
-
+# test if coroutine can get upvalues
 func(){
     var x=1;
     var co=coroutine.create(func(){
-        for(var j=0;j<1024;j+=1){
+        for(var j=0;j<128;j+=1){
             coroutine.yield(x,i,j);
             x+=1;
         }
     });
-    for(var i=0;i<256;i+=1)
+    for(var i=0;i<16;i+=1)
         println(coroutine.resume(co));
-}();
\ No newline at end of file
+}();
+
+# pressure test
+var productor=func(){
+    for(var i=0;;i+=1)
+        coroutine.yield(i);
+}
+var total=10000; # ms
+var co=coroutine.create(productor);
+var tm=maketimestamp();
+
+var counter=0;
+var bar=process_bar.bar("block","point","line",40);
+var consumer=func(){
+    counter+=1;
+    for(var i=0;i<5;i+=1)
+        coroutine.resume(co);
+    var rate=(tm.elapsedMSec()+1)/total;
+    print(bar.bar(rate)," ",rate*100,"%  \r");
+}
+
+tm.stamp();
+while(tm.elapsedMSec()<total)
+    consumer();
+println("\nexecute ",counter," tasks during ",total," ms, avg ",counter/(total)," tasks/ms.")
\ No newline at end of file
diff --git a/test/filesystem.nas b/test/filesystem.nas
index 3891b4f..69f9de4 100644
--- a/test/filesystem.nas
+++ b/test/filesystem.nas
@@ -4,11 +4,6 @@ while((var line=io.readln(fd))!=nil)
 io.close(fd);
 println(io.stat("test/filesystem.nas"));
 
-var dd=unix.opendir("test");
-while(var name=unix.readdir(dd))
-    println(name);
-unix.closedir(dd);
-
 var files=func(dir){
     var dd=unix.opendir(dir);
     var res=[];
@@ -18,17 +13,26 @@ var files=func(dir){
     return res;
 }
 var prt=func(s,path){
-    foreach(var i;files(path)){
-        print(s,i);
-        if(unix.isdir(path~'/'~i)){
-            print(' <dir>\n');
-            if(i!='.' and i!='..')
-                prt(s~' |',path~'/'~i);
+    var vec=files(path);
+    var last=size(vec)-1;
+    forindex(var i;vec){
+        var f=vec[i];
+        if(f=="." or f=="..")
+            continue;
+        foreach(var j;s)
+            print("\e[34m",j,"\e[0m");
+        if(unix.isdir(path~"/"~f)){
+            println("\e[34m",i==last?"└─":"├─","\e[0m\e[36m",f," >\e[0m");
+            append(s,i==last?"  ":"│ ");
+            prt(s,path~"/"~f);
+            pop(s);
+        }elsif(unix.isfile(path~"/"~f)){
+            println("\e[34m",i==last?"└─":"├─","\e[0m\e[32m",f,"\e[0m");
+        }else{
+            println("\e[34m",i==last?"└─":"├─","\e[0m\e[91m",f,"\e[0m");
         }
-        elsif(unix.isfile(path~'/'~i))
-            print(" <file>\n");
-        else
-            print(' <unknown>\n');
     }
 }
-prt('',".");
\ No newline at end of file
+
+println("\e[36mNasal-Interpreter >\e[0m");
+prt([""],".");
\ No newline at end of file