diff --git a/src/nasal_err.cpp b/src/nasal_err.cpp
index 290ce1d..3ff12c0 100644
--- a/src/nasal_err.cpp
+++ b/src/nasal_err.cpp
@@ -137,14 +137,15 @@ void error::err(
     const std::string iden = identation(maxlen);
 
     for(u32 line = loc.begin_line; line<=loc.end_line; ++line) {
+        // skip line 0
         if (!line) {
             continue;
         }
 
         if (loc.begin_line<line && line<loc.end_line) {
             if (line==loc.begin_line+1) {
-                std::cerr << cyan << iden << " | " << reset << "...\n"
-                << cyan << iden << " | " << reset << "\n";
+                std::cerr << cyan << iden << " | " << reset << "...\n";
+                std::cerr << cyan << iden << " | " << reset << "\n";
             }
             continue;
         }
@@ -154,7 +155,12 @@ void error::err(
             continue;
         }
 
-        const std::string& code=res[line-1];
+        // line out of range
+        if (line-1>=res.size()) {
+            continue;
+        }
+
+        const auto& code = res[line-1];
         std::cerr << cyan << leftpad(line, maxlen) << " | " << reset << code << "\n";
         // output underline
         std::cerr << cyan << iden << " | " << reset;
diff --git a/src/nasal_lexer.cpp b/src/nasal_lexer.cpp
index 9b63ab8..7228c6f 100644
--- a/src/nasal_lexer.cpp
+++ b/src/nasal_lexer.cpp
@@ -330,6 +330,7 @@ const error& lexer::scan(const std::string& file) {
     line = 1;
     column = 0;
     ptr = 0;
+    toks = {};
     open(file);
 
     while(ptr<res.size()) {
diff --git a/src/repl.cpp b/src/repl.cpp
index d59207d..a348a2a 100644
--- a/src/repl.cpp
+++ b/src/repl.cpp
@@ -21,7 +21,7 @@ void repl::update_temp_file() {
     for(const auto& i : source) {
         content += i + "\n";
     }
-    info::instance()->repl_file_source = content;
+    info::instance()->repl_file_source = content + " ";
 }
 
 bool repl::check_need_more_input() {
@@ -49,6 +49,7 @@ bool repl::check_need_more_input() {
         if (in_curve<=0 && in_bracket<=0 && in_brace<=0) {
             break;
         }
+
         auto line = readline("... ");
         source.back() += "\n" + line;
     }
@@ -56,19 +57,17 @@ bool repl::check_need_more_input() {
 }
 
 void repl::help() {
-    std::cout << ".h, .help  | show help\n";
-    std::cout << ".e, .exit  | quit the REPL\n";
-    std::cout << ".q, .quit  | quit the REPL\n";
-    std::cout << ".c, .clear | clear the screen\n";
+    std::cout << ".h, .help   | show help\n";
+    std::cout << ".e, .exit   | quit the REPL\n";
+    std::cout << ".q, .quit   | quit the REPL\n";
+    std::cout << ".c, .clear  | clear the screen\n";
+    std::cout << ".s, .source | show source code\n";
     std::cout << "\n";
 }
 
 bool repl::run() {
-    update_temp_file();
-
     using clk = std::chrono::high_resolution_clock;
-    const auto den = clk::duration::period::den;
-    auto start = clk::now();
+    const auto den = clk::duration::period::den;    
 
     auto nasal_lexer = std::unique_ptr<lexer>(new lexer);
     auto nasal_parser = std::unique_ptr<parse>(new parse);
@@ -76,6 +75,8 @@ bool repl::run() {
     auto nasal_opt = std::unique_ptr<optimizer>(new optimizer);
     auto nasal_codegen = std::unique_ptr<codegen>(new codegen);
 
+    auto start = clk::now();
+    update_temp_file();
     if (nasal_lexer->scan("<nasal-repl>").geterr()) {
         return false;
     }
@@ -88,18 +89,18 @@ bool repl::run() {
         return false;
     }
 
-    nasal_opt->do_optimization(nasal_parser->tree());
+    // nasal_opt->do_optimization(nasal_parser->tree());
     if (nasal_codegen->compile(*nasal_parser, *nasal_linker).geterr()) {
         return false;
     }
 
     auto end = clk::now();
     std::clog << "[compile time: " << (end-start).count()*1000.0/den << " ms]\n";
-    runtime->set_detail_report_info(false);
+
     // TODO: gc init stage in this run may cause memory leak,
     // because constant strings will be generated again.
     // but we could not delete old strings, they maybe still on stack.
-    runtime->run(*nasal_codegen, *nasal_linker, {});
+    runtime.run(*nasal_codegen, *nasal_linker, {});
 
     return true;
 }
@@ -117,7 +118,9 @@ void repl::execute() {
             continue;
         }
 
-        if (line == ".e" || line == ".exit" || line == ".q" || line == ".quit") {
+        if (line == ".e" || line == ".exit") {
+            break;
+        } else if (line == ".q" || line == ".quit") {
             break;
         } else if (line == ".h" || line == ".help") {
             help();
@@ -125,6 +128,10 @@ void repl::execute() {
         } else if (line == ".c" || line == ".clear") {
             std::cout << "\033c";
             continue;
+        } else if (line == ".s" || line == ".source") {
+            update_temp_file();
+            std::cout << info::instance()->repl_file_source << "\n";
+            continue;
         } else if (line[0] == "."[0]) {
             std::cout << "no such command \"" << line;
             std::cout << "\", input \".help\" for help\n";
diff --git a/src/repl.h b/src/repl.h
index 3aa5b81..ea677c5 100644
--- a/src/repl.h
+++ b/src/repl.h
@@ -27,7 +27,7 @@ struct info {
 class repl {
 private:
     std::vector<std::string> source;
-    std::unique_ptr<vm> runtime;
+    vm runtime;
 
 private:
     std::string readline(std::string);
@@ -37,8 +37,11 @@ private:
     bool run();
 
 public:
-    repl(): runtime(std::unique_ptr<vm>(new vm)) {
-        runtime->set_repl_mode_flag(true);
+    repl() {
+        // set repl mode
+        runtime.set_repl_mode_flag(true);
+        // no detail report info
+        runtime.set_detail_report_info(false);
     }
     void execute();
 };
diff --git a/tools/repl.nas b/tools/repl.nas
deleted file mode 100644
index 74a3cc2..0000000
--- a/tools/repl.nas
+++ /dev/null
@@ -1,76 +0,0 @@
-# experimental repl
-# 2023/8/19 by ValKmjolnir
-
-var help = func() {
-    println(" .help   | show help");
-    println(" .exit   | quit the REPL");
-    println(" .quit   | quit the REPL");
-    println(" .clear  | clear the screen");
-    println();
-}
-
-var content = [];
-var log_cache = "";
-
-println("Nasal: This is experimental REPL");
-println("Tips : \";\" is automatically added at the end of the input line.");
-help();
-
-var count_bracket = func(line) {
-    var len = size(line);
-    var count = 0;
-    for(var i = 0; i < len; i += 1) {
-        if (line[i] == "{"[0]) {
-            count += 1;
-        } elsif (line[i] == "}"[0]) {
-            count -= 1;
-        }
-    }
-    return count;
-}
-
-while(1) {
-    var line = readline(">>> ");
-    if (!size(line)) {
-        continue;
-    }
-    if (line == ".exit" or line == ".quit") {
-        break;
-    } elsif (line == ".help") {
-        println();
-        help();
-        continue;
-    } elsif (line == ".clear") {
-        print("\ec");
-        continue;
-    } elsif (line[0] == "."[0]) {
-        println("no such command \"", line, "\", input \".help\" for help\n");
-        continue;
-    }
-    var in_bracket_level = count_bracket(line);
-    while(in_bracket_level > 0) {
-        var temp_line = readline("... ");
-        in_bracket_level += count_bracket(temp_line);
-        line ~= temp_line ~ "\n";
-    }
-
-    append(content, line);
-
-    var source = "";
-    foreach(var i; content) {
-        source ~= i ~ ";\n";
-    }
-
-    io.fout(".temp.nas", source);
-    var result = system("nasal .temp.nas > .temp.log");
-    if (result != 0) {
-        pop(content);
-        continue;
-    }
-
-    var log = io.readfile(".temp.log");
-    if (size(log) and size(log) != size(log_cache)) {
-        println(substr(log, size(log_cache), size(log)), "\n");
-        log_cache = log;
-    }
-}
\ No newline at end of file