diff --git a/nasal_codegen.h b/nasal_codegen.h
index 815bb5e..eb66dd5 100644
--- a/nasal_codegen.h
+++ b/nasal_codegen.h
@@ -14,10 +14,9 @@ enum op_code
     op_pzero,    // push 0 to the stack
     op_pnil,     // push constant nil to the stack
     op_pstr,     // push constant string to the stack
-    op_newv,     // push new vector to the stack
+    op_newv,     // push new vector with initial values from stack
     op_newh,     // push new hash to the stack
     op_newf,     // push new function to the stack
-    op_vapp,     // vector append
     op_happ,     // hash append
     op_para,     // normal  parameter
     op_defpara,  // default parameter
@@ -88,7 +87,6 @@ struct
     {op_newv,     "newv  "},
     {op_newh,     "newh  "},
     {op_newf,     "newf  "},
-    {op_vapp,     "vapp  "},
     {op_happ,     "happ  "},
     {op_para,     "para  "},
     {op_defpara,  "def   "},
@@ -164,15 +162,15 @@ private:
     int error;
     int in_forindex;
     int in_foreach;
-    std::unordered_map<double,int>       number_table;
-    std::unordered_map<std::string,int>  string_table;
-    std::vector<double>                  num_res_table;
-    std::vector<std::string>             str_res_table;
-    std::vector<opcode>                  exec_code;
-    std::list<std::vector<int> >         continue_ptr;
-    std::list<std::vector<int> >         break_ptr;
-    std::vector<std::string>             global;
-    std::list<std::vector<std::string> > local;
+    std::unordered_map<double,int>      number_table;
+    std::unordered_map<std::string,int> string_table;
+    std::vector<double>                 num_res_table;
+    std::vector<std::string>            str_res_table;
+    std::vector<opcode>                 exec_code;
+    std::list<std::vector<int>>         continue_ptr;
+    std::list<std::vector<int>>         break_ptr;
+    std::vector<std::string>            global;
+    std::list<std::vector<std::string>> local;
     
     void die(std::string,int);
     void regist_number(double);
@@ -325,10 +323,9 @@ void nasal_codegen::str_gen(nasal_ast& ast)
 
 void nasal_codegen::vec_gen(nasal_ast& ast)
 {
-    gen(op_newv,0);
     for(auto& node:ast.get_children())
         calc_gen(node);
-    gen(op_vapp,ast.get_children().size());
+    gen(op_newv,ast.get_children().size());
     return;
 }
 
diff --git a/nasal_gc.h b/nasal_gc.h
index ce2f94f..489d4da 100644
--- a/nasal_gc.h
+++ b/nasal_gc.h
@@ -242,7 +242,7 @@ std::string nasal_val::to_string()
 
 struct nasal_gc
 {
-#define STACK_MAX_DEPTH (65536<<2)
+#define STACK_MAX_DEPTH (65536<<1)
     nasal_val*              zero_addr;               // reserved address of nasal_val,type vm_num, 0
     nasal_val*              one_addr;                // reserved address of nasal_val,type vm_num, 1
     nasal_val*              nil_addr;                // reserved address of nasal_val,type vm_nil
@@ -254,7 +254,7 @@ struct nasal_gc
     std::vector<nasal_val*> memory;                  // gc memory
     std::queue <nasal_val*> free_list[vm_type_size]; // gc free list
     std::vector<nasal_val*> global;
-    std::list<std::vector<nasal_val*> > local;
+    std::list<std::vector<nasal_val*>> local;
     void                    mark();
     void                    sweep();
     void                    gc_init(std::vector<double>&,std::vector<std::string>&);
diff --git a/nasal_vm.h b/nasal_vm.h
index 58d9807..f58df80 100644
--- a/nasal_vm.h
+++ b/nasal_vm.h
@@ -32,7 +32,6 @@ private:
     void opr_newv();
     void opr_newh();
     void opr_newf();
-    void opr_vapp();
     void opr_happ();
     void opr_para();
     void opr_defpara();
@@ -150,12 +149,12 @@ void nasal_vm::opr_intg()
 void nasal_vm::opr_intl()
 {
     (*stack_top)->ptr.func->closure.resize(exec_code[pc].num,gc.nil_addr);
-    (*stack_top)->ptr.func->closure[0]=gc.nil_addr;// me
     return;
 }
 void nasal_vm::opr_offset()
 {
     (*stack_top)->ptr.func->offset=exec_code[pc].num;
+    return;
 }
 void nasal_vm::opr_loadg()
 {
@@ -194,8 +193,14 @@ void nasal_vm::opr_pstr()
 }
 void nasal_vm::opr_newv()
 {
-    nasal_val* vec=gc.gc_alloc(vm_vec);
-    *(++stack_top)=vec;
+    nasal_val*  vec_addr=gc.gc_alloc(vm_vec);
+    nasal_val** begin=stack_top-exec_code[pc].num+1;
+    auto& vec=vec_addr->ptr.vec->elems;// stack_top-exec_code[pc].num stores the vector
+    vec.resize(exec_code[pc].num);
+    for(int i=0;i<exec_code[pc].num;++i)
+        vec[i]=begin[i];
+    stack_top=begin;
+    *stack_top=vec_addr;
     return;
 }
 void nasal_vm::opr_newh()
@@ -215,16 +220,6 @@ void nasal_vm::opr_newf()
     *(++stack_top)=val;
     return;
 }
-void nasal_vm::opr_vapp()
-{
-    nasal_val** begin=stack_top-exec_code[pc].num+1;
-    auto& vec=begin[-1]->ptr.vec->elems;// stack_top-exec_code[pc].num stores the vector
-    vec.resize(exec_code[pc].num);
-    for(int i=0;i<exec_code[pc].num;++i)
-        vec[i]=begin[i];
-    stack_top=begin-1;
-    return;
-}
 void nasal_vm::opr_happ()
 {
     nasal_val* val=*stack_top--;
@@ -723,14 +718,14 @@ void nasal_vm::opr_slcend()
 void nasal_vm::opr_slc()
 {
     nasal_val* val=*stack_top--;
-    double num;
+    int num;
     switch(val->type)
     {
-        case vm_num:num=val->ptr.num;break;
-        case vm_str:num=str2num(val->ptr.str->c_str());break;
+        case vm_num:num=(int)val->ptr.num;break;
+        case vm_str:num=(int)str2num(val->ptr.str->c_str());break;
         default:die("slc: error value type");break;
     }
-    nasal_val* res=(*stack_top)->ptr.vec->get_val((int)num);
+    nasal_val* res=(*stack_top)->ptr.vec->get_val(num);
     if(!res)
         die("slc: index out of range");
     gc.slice_stack.back()->ptr.vec->elems.push_back(res);
@@ -762,13 +757,18 @@ void nasal_vm::opr_slc2()
         die("slc2: begin index must be less than end index");
         return;
     }
-    if(num1<-ref_size || num1>=ref_size || num2<-ref_size || num2>=ref_size)
+    else if(num1<-ref_size || num1>=ref_size)
     {
-        die("slc2: begin or end index out of range");
+        die("slc2: begin index out of range: "+num2str(num1));
+        return;
+    }
+    else if(num2<-ref_size || num2>=ref_size)
+    {
+        die("slc2: end index out of range: "+num2str(num2));
         return;
     }
     for(int i=num1;i<=num2;++i)
-        aim.push_back(ref[i]);
+        aim.push_back(i>=0?ref[i]:ref[i+ref_size]);
     return;
 }
 void nasal_vm::opr_mcallg()
@@ -849,6 +849,7 @@ void nasal_vm::opr_ret()
     pc=ret.top();
     ret.pop();
     nasal_val* ret_val=*stack_top--;
+    (*stack_top)->ptr.func->closure[0]=gc.nil_addr;// set me to nil
     *stack_top=ret_val;
     return;
 }
@@ -870,7 +871,6 @@ void nasal_vm::run()
         &nasal_vm::opr_newv,
         &nasal_vm::opr_newh,
         &nasal_vm::opr_newf,
-        &nasal_vm::opr_vapp,
         &nasal_vm::opr_happ,
         &nasal_vm::opr_para,
         &nasal_vm::opr_defpara,
diff --git a/test/ascii-art.nas b/test/ascii-art.nas
index 2594565..bad2dbe 100644
--- a/test/ascii-art.nas
+++ b/test/ascii-art.nas
@@ -4,7 +4,7 @@ var char_ttf=[
     ["    ████╗","   ██╔██║","  ██╔╝██║"," ███████║","██╔═══██║","╚═╝   ╚═╝"],
     ["██████╗ ","██╔══██╗","██████╔╝","██╔══██╗","██████╔╝","╚═════╝ "],
     [" ██████╗","██╔════╝","██║     ","██║     ","╚██████╗"," ╚═════╝"],
-    ["██████╗ ","██╔══██╗","██║  ██║","██║  ██║","██████╔╝","╚═════╝  "],
+    ["██████╗ ","██╔══██╗","██║  ██║","██║  ██║","██████╔╝","╚═════╝ "],
     ["███████╗","██╔════╝","█████╗  ","██╔══╝  ","███████╗","╚══════╝"],
     ["███████╗","██╔════╝","█████╗  ","██╔══╝  ","██║     ","╚═╝     "],
     [" █████╗ ","██╔═══╝ ","██║ ██╗ ","██║ ╚██╗","╚█████╔╝"," ╚════╝ "],