diff --git a/balloon/abstract_syntax_tree.cpp b/balloon/abstract_syntax_tree.cpp
index 56bbb3a..55389e0 100644
--- a/balloon/abstract_syntax_tree.cpp
+++ b/balloon/abstract_syntax_tree.cpp
@@ -894,8 +894,8 @@ var abstract_syntax_tree::run_func(std::list<var> parameter,var self_func)
 	
 	scope.add_new_var(self_func);
 	
-	abstract_syntax_tree para=children.front();
-	abstract_syntax_tree blk=children.back();
+	abstract_syntax_tree para=children.front();// get parameter name(declared in function)
+	abstract_syntax_tree blk=children.back();  // get block
 	std::list<abstract_syntax_tree>::iterator para_name=para.children.begin();
 	std::list<var>::iterator para_value=parameter.begin();
 	
@@ -939,6 +939,7 @@ var abstract_syntax_tree::run_func(std::list<var> parameter,var self_func)
 			if(exit_type==__error_value_type)
 				break;
 		}
+		// this must be added when running a function
 		ret.set_type(__var_number);
 		if(exit_type!=__error_value_type)
 			ret.set_number(1);
@@ -946,6 +947,37 @@ var abstract_syntax_tree::run_func(std::list<var> parameter,var self_func)
 			ret.set_number(0);
 		ret_stack.push(ret);
 	}
+	else if(self_func.get_name()=="append")
+	{
+		if(!parameter.empty())
+		{
+			std::list<var>::iterator i=parameter.begin();
+			var* array_addr=scope.append_get_addr(i->get_name());
+			if(array_addr!=&error_var)
+			{
+				++i;
+				for(;i!=parameter.end();++i)
+					array_addr->append_array(*i);
+			}
+			else
+			{
+				std::cout<<">>[Runtime-error] line "<<line<<": cannot find a var named \'"<<parameter.begin()->get_name()<<"\'."<<std::endl;
+				exit_type=__find_var_failure;
+			}
+		}
+		else
+		{
+			exit_type=__lack_parameter;
+			std::cout<<">>[Runtime-error] line "<<line<<": lack parameter(s)."<<std::endl;
+		}
+		// this must be added when running a function
+		ret.set_type(__var_number);
+		if(exit_type!=__find_var_failure)
+			ret.set_number(1);
+		else
+			ret.set_number(0);
+		ret_stack.push(ret);
+	}
 	else
 	{
 		for(;para_name!=para.children.end();++para_name,++para_value)
@@ -961,6 +993,7 @@ var abstract_syntax_tree::run_func(std::list<var> parameter,var self_func)
 			new_var.set_name(para_name->name);
 			scope.add_new_var(new_var);
 		}
+		// this must be added when running a function
 		if(exit_type==__process_exited_successfully)
 		{
 			int _t=blk.run_block();
diff --git a/balloon/balloon_scope.h b/balloon/balloon_scope.h
index 10e8488..ac49af7 100644
--- a/balloon/balloon_scope.h
+++ b/balloon/balloon_scope.h
@@ -45,14 +45,16 @@ class balloon_scope
 		{
 			if(!scope_list.empty() && !scope_list.back().empty())
 			{
-				
 				std::list<std::list<var> >::iterator i=scope_list.back().end();
 				--i;
 				for(;;--i)
 				{
-					for(std::list<var>::iterator j=i->begin();j!=i->end();++j)
-						if(j->get_name()==name)
-							return true;
+					if(!i->empty())
+					{
+						for(std::list<var>::iterator j=i->begin();j!=i->end();++j)
+							if(j->get_name()==name)
+								return true;
+					}
 					if(i==scope_list.back().begin())
 						break;
 				}
@@ -77,6 +79,27 @@ class balloon_scope
 			global.push_back(t);
 			return;
 		}
+		void print_last_block()
+		{
+			if(!scope_list.empty() && !scope_list.back().empty())
+			{
+				std::list<std::list<var> >::iterator i=scope_list.back().end();
+				--i;
+				// get the last scope block(std::list<std::list<var> >)
+				for(;;--i)
+				{
+					if(!i->empty())
+					{
+						for(std::list<var>::iterator j=i->begin();j!=i->end();++j)
+							std::cout<<j->get_name()<<std::endl;
+					
+					}
+					if(i==scope_list.back().begin())
+						break;
+				}
+			}
+			return;
+		}
 		var get_var(std::string name)
 		{
 			if(!scope_list.empty() && !scope_list.back().empty())
@@ -86,9 +109,12 @@ class balloon_scope
 				// get the last scope block(std::list<std::list<var> >)
 				for(;;--i)
 				{
-					for(std::list<var>::iterator j=i->begin();j!=i->end();++j)
-						if(j->get_name()==name)
-							return *j;
+					if(!i->empty())
+					{
+						for(std::list<var>::iterator j=i->begin();j!=i->end();++j)
+							if(j->get_name()==name)
+								return *j;
+					}
 					if(i==scope_list.back().begin())
 						break;
 				}
@@ -101,24 +127,70 @@ class balloon_scope
 			}
 			return error_var;
 		}
+		var* append_get_addr(std::string name)
+		{
+			var* addr=NULL;
+			if(!scope_list.empty())
+			{
+				int cnt=1;
+				std::list<std::list<std::list<var> > >::iterator blk=scope_list.end();
+				--blk;
+				for(;;--blk,++cnt)
+				{
+					if(!blk->empty())
+					{
+						std::list<std::list<var> >::iterator i=blk->end();
+						--i;
+						for(;;--i)
+						{
+							if(!i->empty())
+							{
+								for(std::list<var>::iterator j=i->begin();j!=i->end();++j)
+									if(j->get_name()==name)
+									{
+										addr=&(*j);
+										return addr;
+									}
+							}
+							if(i==blk->begin())
+								break;
+						}	
+					}
+					if(cnt==2 || blk==scope_list.begin())
+						break;
+				}
+			}
+			if(!global.empty())
+			{
+				for(std::list<var>::iterator i=global.begin();i!=global.end();++i)
+					if(i->get_name()==name)
+					{
+						addr=&(*i);
+						return addr;
+					}
+			}
+			return &error_var;
+		}
 		var* get_addr(std::string name)
 		{
 			var* addr=NULL;
-			if(!scope_list.empty() && !scope_list.back().empty())
+			if(!scope_list.empty())
 			{
 				std::list<std::list<var> >::iterator i=scope_list.back().end();
 				--i;
-				// get the last scope block(std::list<std::list<var> >)
 				for(;;--i)
 				{
-					for(std::list<var>::iterator j=i->begin();j!=i->end();++j)
-						if(j->get_name()==name)
-						{
-							addr=&(*j);
-							return addr;
-						}
-					if(i==scope_list.back().begin())
-						break;
+					if(!i->empty())
+					{
+						for(std::list<var>::iterator j=i->begin();j!=i->end();++j)
+							if(j->get_name()==name)
+							{
+								addr=&(*j);
+								return addr;
+							}
+						if(i==scope_list.back().begin())
+							break;
+					}
 				}
 			}
 			if(!global.empty())
diff --git a/balloon/lib/basics.nas b/balloon/lib/basics.nas
index 98eb592..996daf2 100644
--- a/balloon/lib/basics.nas
+++ b/balloon/lib/basics.nas
@@ -1,12 +1,12 @@
 # this file includes functions:
 #   append
 #   subvec
-var append(vector,elements...)
+var append=func(vector,elements...)
 {
     return __call_special_inline_function(vector,elements);
 };
 
-var subvec(vector,begin,length)
+var subvec=func(vector,begin,length)
 {
     var new_vector=[];
     for(var i=begin;i<begin+length;i+=1)
@@ -16,7 +16,7 @@ var subvec(vector,begin,length)
     return new_vector;
 };
 
-var int(value)
+var int=func(value)
 {
     return __call_Cpp_int(value);
 };
\ No newline at end of file
diff --git a/balloon/main.cpp b/balloon/main.cpp
index 90eeeed..75c82bc 100644
--- a/balloon/main.cpp
+++ b/balloon/main.cpp
@@ -3,10 +3,10 @@
 resource_file prog;
 balloon_lexer lex;
 balloon_parse pas;
+std::string command;
 
 int main()
 {
-	std::string command;
 	std::cout<<">> Balloon interpreter by ValKmjolnir"<<std::endl;
 	std::cout<<">> Input [help] to find help."<<std::endl;
 	while(1)