diff --git a/nasal.h b/nasal.h
index 520abd6..6c6fd35 100644
--- a/nasal.h
+++ b/nasal.h
@@ -148,6 +148,14 @@ int utf8_hdchk(char head)
     return nbytes;
 }
 
+std::string chrhex(const char c)
+{
+    std::string res="";
+    res+="0123456789abcdef"[(c&0xf0)>>4];
+    res+="0123456789abcdef"[c&0x0f];
+    return res;
+}
+
 std::string rawstr(const std::string& str)
 {
     std::string ret("");
@@ -159,8 +167,7 @@ std::string rawstr(const std::string& str)
         if(i<=0)
         {
             ret+="\\x";
-            ret+="0123456789abcdef"[(i>>4)&15];
-            ret+="0123456789abcdef"[i&15];
+            ret+=chrhex(i);
             continue;
         }
 #endif
diff --git a/nasal_err.h b/nasal_err.h
index cda2f53..1edacf9 100644
--- a/nasal_err.h
+++ b/nasal_err.h
@@ -46,31 +46,24 @@ private:
     uint32_t error;
 public:
     nasal_err():error(0){}
-    void err(const char* stage,const std::string& info,const char end='\n')
+    void err(const char* stage,const std::string& info)
     {
         ++error;
-        std::cerr<<"["<<stage<<"] "<<info<<end;
+        std::cerr<<"["<<stage<<"] "<<info<<"\n";
     }
     void err(const char* stage,uint32_t line,uint32_t column,const std::string& info)
     {
         ++error;
-        if(!line)
-        {
-            std::cerr<<"["<<stage<<"] "<<file<<": "<<info<<'\n';
-            return;
-        }
-        std::cerr<<"["<<stage<<"] "<<file<<":"<<line<<":"<<column<<" "<<info<<"\n"<<res[line-1]<<'\n';
+        const std::string& code=res[line-1];
+        std::cerr<<"["<<stage<<"] "<<file<<":"<<line<<":"<<column<<" "<<info<<"\n"<<code<<"\n";
         for(int i=0;i<(int)column-1;++i)
-            std::cerr<<char(" \t"[res[line-1][i]=='\t']);
+            std::cerr<<char(" \t"[code[i]=='\t']);
         std::cerr<<"^\n";
     }
     void err(const char* stage,uint32_t line,const std::string& info)
     {
         ++error;
-        if(!line)
-            std::cerr<<"["<<stage<<"] "<<file<<": "<<info<<'\n';
-        else
-            std::cerr<<"["<<stage<<"] "<<file<<":"<<line<<" "<<info<<"\n"<<res[line-1]<<'\n';
+        std::cerr<<"["<<stage<<"] "<<file<<":"<<line<<" "<<info<<"\n"<<res[line-1]<<'\n';
     }
     void chkerr(){if(error)std::exit(1);}
 };
diff --git a/nasal_import.h b/nasal_import.h
index e566d1c..6b5c898 100644
--- a/nasal_import.h
+++ b/nasal_import.h
@@ -87,10 +87,14 @@ nasal_ast nasal_import::lib_import()
 
     const std::vector<std::string> libpath=
     {
-        "lib.nas",
-        "stl/lib.nas"
+#ifdef __WIN32
+        ".\\lib.nas",
+        ".\\stl\\lib.nas"
+#else
+        "./lib.nas",
+        "./stl/lib.nas"
+#endif
     };
-
     std::string filename="";
     for(auto& i:libpath)
         if(access(i.c_str(),F_OK)!=-1)
@@ -103,7 +107,7 @@ nasal_ast nasal_import::lib_import()
         std::string paths="";
         for(auto& i:libpath)
             paths+="  "+i+"\n";
-        nerr.err("link","cannot find lib file in these paths:\n"+paths,' ');
+        nerr.err("link","cannot find lib file in these paths:\n"+paths);
         nerr.chkerr();
         return {0,ast_root};
     }
diff --git a/nasal_lexer.h b/nasal_lexer.h
index 84d4568..11106b3 100644
--- a/nasal_lexer.h
+++ b/nasal_lexer.h
@@ -15,11 +15,14 @@
 
 enum token_type
 {
-    tok_null=0,// null token default token type
-    tok_num,   // number     basic token type
-    tok_str,   // string     basic token type
-    tok_id,    // identifier basic token type
-    tok_for,tok_forindex,tok_foreach,tok_while,
+    tok_null=0,  // null token (default token type)
+    tok_num,     // number     basic token type
+    tok_str,     // string     basic token type
+    tok_id,      // identifier basic token type
+    tok_for,     // loop keyword for
+    tok_forindex,// loop keyword forindex
+    tok_foreach, // loop keyword foreach
+    tok_while,   // loop keyword while
     tok_var,tok_func,tok_break,tok_continue,
     tok_ret,tok_if,tok_elsif,tok_else,tok_nil,
     tok_lcurve,tok_rcurve,
@@ -106,20 +109,24 @@ class nasal_lexer
 private:
     uint32_t    line;
     uint32_t    column;
-    uint32_t    ptr;
+    size_t      ptr;
     nasal_err&  nerr;
     std::string res;
     std::vector<token> tokens;
 
     uint32_t get_type(const std::string&);
-    void die(std::string info){nerr.err("lexer",line,column,info);};
+    void die(const std::string& info){nerr.err("lexer",line,column,info);}
     void open(const std::string&);
     std::string utf8_gen();
     std::string id_gen();
     std::string num_gen();
     std::string str_gen();
 public:
-    nasal_lexer(nasal_err& e):line(0),column(0),ptr(0),nerr(e){}
+    nasal_lexer(nasal_err& e):
+        line(1),
+        column(0),
+        ptr(0),
+        nerr(e){}
     void scan(const std::string&);
     void print();
     const std::vector<token>& get_tokens() const {return tokens;}
@@ -162,16 +169,25 @@ std::string nasal_lexer::utf8_gen()
         if(nbytes)
         {
             tmp+=res[ptr++];
-            for(uint32_t i=0;i<nbytes;++i,++ptr)
+            ++column;
+            for(uint32_t i=0;i<nbytes;++i,++ptr,++column)
                 if(ptr<res.size() && (res[ptr]&0xc0)==0x80)
                     tmp+=res[ptr];
             if(tmp.length()!=1+nbytes)
-                die("invalid utf-8 character here");
+            {
+                std::string utf_info="0x"+chrhex(tmp[0]);
+                for(uint32_t i=1;i<tmp.size();++i)
+                    utf_info+=" 0x"+chrhex(tmp[i]);
+                die("invalid utf-8 character `"+utf_info+"`, make sure this is a text file.");
+                std::exit(1);
+            }
             str+=tmp;
-            ++column;
         }
         else
+        {
             ++ptr;
+            ++column;
+        }
     }
     return str;
 }
@@ -203,7 +219,7 @@ std::string nasal_lexer::num_gen()
             str+=res[ptr++];
         column+=str.length();
         if(str.length()<3)// "0x"
-            die("invalid number:"+str);
+            die("invalid number `"+str+"`.");
         return str;
     }
     // generate oct number
@@ -215,7 +231,7 @@ std::string nasal_lexer::num_gen()
             str+=res[ptr++];
         column+=str.length();
         if(str.length()<3)// "0o"
-            die("invalid number:"+str);
+            die("invalid number `"+str+"`.");
         return str;
     }
     // generate dec number
@@ -232,7 +248,7 @@ std::string nasal_lexer::num_gen()
         if(str.back()=='.')
         {
             column+=str.length();
-            die("invalid number:"+str);
+            die("invalid number `"+str+"`.");
             return "0";
         }
     }
@@ -247,7 +263,7 @@ std::string nasal_lexer::num_gen()
         if(str.back()=='e' || str.back()=='E' || str.back()=='-' || str.back()=='+')
         {
             column+=str.length();
-            die("invalid number:"+str);
+            die("invalid number `"+str+"`.");
             return "0";
         }
     }
@@ -315,7 +331,7 @@ void nasal_lexer::scan(const std::string& file)
     std::string str;
     while(ptr<res.size())
     {
-        while(ptr<res.size() && (res[ptr]==' ' || res[ptr]=='\n' || res[ptr]=='\t' || res[ptr]=='\r'))// || res[ptr]<0))
+        while(ptr<res.size() && (res[ptr]==' ' || res[ptr]=='\n' || res[ptr]=='\t' || res[ptr]=='\r' || res[ptr]==0))
         {
             // these characters will be ignored, and '\n' will cause ++line
             ++column;
@@ -348,7 +364,7 @@ void nasal_lexer::scan(const std::string& file)
             ++column;
             uint32_t type=get_type(str);
             if(!type)
-                die("invalid operator:"+str);
+                die("invalid operator `"+str+"`.");
             tokens.push_back({line,column,type,str});
             ++ptr;
         }
@@ -375,8 +391,8 @@ void nasal_lexer::scan(const std::string& file)
         else
         {
             ++column;
-            ++ptr;
-            die("unknown character.");
+            char c=res[ptr++];
+            die("invalid character 0x"+chrhex(c)+".");
         }
     }
     tokens.push_back({line,column,tok_eof,"eof"});
diff --git a/nasal_parse.h b/nasal_parse.h
index 6c5e0e2..1d68591 100644
--- a/nasal_parse.h
+++ b/nasal_parse.h
@@ -48,7 +48,7 @@ private:
     nasal_ast root;
     nasal_err& nerr;
 
-    void die(uint32_t,std::string);
+    void die(uint32_t,std::string,bool);
     void match(uint32_t type,const char* info=nullptr);
     bool check_comma(const uint32_t*);
     bool check_multi_scalar();
@@ -117,15 +117,20 @@ void nasal_parse::compile(const nasal_lexer& lexer)
             match(tok_semi);
         // the last expression can be recognized without semi
         else if(need_semi_check(root.child().back()) && tokens[ptr].type!=tok_eof)
-            die(error_line,"expected \";\"");
+            die(error_line,"expected \";\"",true);
     }
     nerr.chkerr();
 }
-void nasal_parse::die(uint32_t line,std::string info)
+void nasal_parse::die(uint32_t line,std::string info,bool report_prev=false)
 {
     int col=(int)tokens[ptr].column-(int)tokens[ptr].str.length();
     if(tokens[ptr].type==tok_str)
         col-=2; // tok_str's str has no \"
+    if(report_prev && ptr-1>=0) // used to report lack of ',' ';'
+    {
+        line=tokens[ptr-1].line;
+        col=tokens[ptr-1].column+1;
+    }
     nerr.err("parse",line,col<0?0:col,info);
 }
 void nasal_parse::match(uint32_t type,const char* info)
@@ -155,7 +160,7 @@ bool nasal_parse::check_comma(const uint32_t* panic_set)
     for(uint32_t i=0;panic_set[i];++i)
         if(tokens[ptr].type==panic_set[i])
         {
-            die(error_line,"expected \',\' between scalars");
+            die(error_line,"expected \',\' between scalars",true);
             return true;
         }
     return false;
@@ -309,7 +314,7 @@ nasal_ast nasal_parse::hash()
         if(tokens[ptr].type==tok_comma)
             match(tok_comma);
         else if(tokens[ptr].type==tok_id || tokens[ptr].type==tok_str)// first set of hashmember
-            die(error_line,"expected \',\' between hash members");
+            die(error_line,"expected \',\' between hash members",true);
         else
             break;
     }
@@ -377,7 +382,7 @@ nasal_ast nasal_parse::args()
         if(tokens[ptr].type==tok_comma)
             match(tok_comma);
         else if(tokens[ptr].type==tok_id)// first set of identifier
-            die(error_line,"expected \',\' between identifiers");
+            die(error_line,"expected \',\' between identifiers",true);
         else
             break;
     }
@@ -484,7 +489,7 @@ nasal_ast nasal_parse::exprs()
                 match(tok_semi);
             // the last expression can be recognized without semi
             else if(need_semi_check(node.child().back()) && tokens[ptr].type!=tok_rbrace)
-                die(error_line,"expected \";\"");
+                die(error_line,"expected \';\'",true);
         }
         match(tok_rbrace,"expected \'}\' when generating expressions");
     }
@@ -796,7 +801,7 @@ nasal_ast nasal_parse::multi_id()
         if(tokens[ptr].type==tok_comma)
             match(tok_comma);
         else if(tokens[ptr].type==tok_id)// first set of identifier
-            die(error_line,"expected \',\' between identifiers");
+            die(error_line,"expected \',\' between identifiers",true);
         else
             break;
     }