diff --git a/Cargo.lock b/Cargo.lock
index 0e03084b..498b54b7 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -81,7 +81,7 @@ dependencies = [
 
 [[package]]
 name = "calcit_runner"
-version = "0.3.0-a8"
+version = "0.3.0-a9"
 dependencies = [
  "cirru_edn",
  "cirru_parser",
diff --git a/Cargo.toml b/Cargo.toml
index 2908d1b5..d310ebff 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "calcit_runner"
-version = "0.3.0-a8"
+version = "0.3.0-a9"
 authors = ["jiyinyiyong <jiyinyiyong@gmail.com>"]
 edition = "2018"
 license = "MIT"
diff --git a/calcit/snapshots/test-string.cirru b/calcit/snapshots/test-string.cirru
index a5caa244..1be932ca 100644
--- a/calcit/snapshots/test-string.cirru
+++ b/calcit/snapshots/test-string.cirru
@@ -125,6 +125,10 @@
               assert= "|do 's"
                 trim $ write-cirru-edn 's
 
+              assert= (escape "|\n") "|\"\\n\""
+              assert= (escape "|\t") "|\"\\t\""
+              assert= (escape "|a") "|\"a\""
+
         |test-char $ quote
           fn ()
             log-title "|Test char"
diff --git a/package.json b/package.json
index d10a7740..a6741970 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@calcit/procs",
-  "version": "0.3.0-a8",
+  "version": "0.3.0-a9",
   "main": "./lib/calcit.procs.js",
   "devDependencies": {
     "@types/node": "^14.14.41",
diff --git a/src/builtins.rs b/src/builtins.rs
index 1aaac9e0..b401cfda 100644
--- a/src/builtins.rs
+++ b/src/builtins.rs
@@ -42,6 +42,8 @@ pub fn is_proc_name(s: &str) -> bool {
       | "quit"
       | "get-env"
       | "&get-calcit-backend"
+      | "read-file"
+      | "write-file"
       // logics
       | "&="
       | "&<"
@@ -87,6 +89,7 @@ pub fn is_proc_name(s: &str) -> bool {
       | "re-find-index"
       | "re-find-all"
       | "blank?"
+      | "escape"
       // lists
       | "[]"
       | "'" // used as an alias for `[]`, experimental
@@ -126,6 +129,8 @@ pub fn is_proc_name(s: &str) -> bool {
       // refs
       | "deref"
       | "reset!"
+      | "add-watch"
+      | "remove-watch"
       // records
       | "new-record"
       | "&%{}"
@@ -162,6 +167,8 @@ pub fn handle_proc(name: &str, args: &CalcitItems) -> Result<Calcit, String> {
     "quit" => effects::quit(args),
     "get-env" => effects::get_env(args),
     "&get-calcit-backend" => effects::call_get_calcit_backend(args),
+    "read-file" => effects::read_file(args),
+    "write-file" => effects::write_file(args),
     // logics
     "&=" => logics::binary_equal(args),
     "&<" => logics::binary_less(args),
@@ -203,6 +210,7 @@ pub fn handle_proc(name: &str, args: &CalcitItems) -> Result<Calcit, String> {
     "parse-float" => strings::parse_float(args),
     "pr-str" => strings::pr_str(args),
     "blank?" => strings::blank_ques(args),
+    "escape" => strings::escape(args),
     // regex
     "re-matches" => regexes::re_matches(args),
     "re-find" => regexes::re_find(args),
@@ -247,6 +255,8 @@ pub fn handle_proc(name: &str, args: &CalcitItems) -> Result<Calcit, String> {
     // refs
     "deref" => refs::deref(args),
     "reset!" => refs::reset_bang(args),
+    "add-watch" => refs::add_watch(args),
+    "remove-watch" => refs::add_watch(args),
     // records
     "new-record" => records::new_record(args),
     "&%{}" => records::call_record(args),
diff --git a/src/builtins/effects.rs b/src/builtins/effects.rs
index 844fc42b..7b9d5e00 100644
--- a/src/builtins/effects.rs
+++ b/src/builtins/effects.rs
@@ -1,4 +1,5 @@
 use std::env;
+use std::fs;
 use std::process::exit;
 use std::sync::Mutex;
 use std::time::Instant;
@@ -118,3 +119,25 @@ pub fn get_env(xs: &CalcitItems) -> Result<Calcit, String> {
     None => Err(String::from("get-env expected an argument, got nothing")),
   }
 }
+
+pub fn read_file(xs: &CalcitItems) -> Result<Calcit, String> {
+  match xs.get(0) {
+    Some(Calcit::Str(s)) => match fs::read_to_string(s) {
+      Ok(content) => Ok(Calcit::Str(content)),
+      Err(e) => Err(format!("read-file failed: {}", e)),
+    },
+    Some(a) => Err(format!("read-file expected a string, got: {}", a)),
+    None => Err(String::from("read-file expected a filename, got nothing")),
+  }
+}
+
+pub fn write_file(xs: &CalcitItems) -> Result<Calcit, String> {
+  match (xs.get(0), xs.get(1)) {
+    (Some(Calcit::Str(path)), Some(Calcit::Str(content))) => match fs::write(path, content) {
+      Ok(_) => Ok(Calcit::Nil),
+      Err(e) => Err(format!("write-file failed, {}", e)),
+    },
+    (Some(a), Some(b)) => Err(format!("write-file expected 3 strings, got: {} {}", a, b)),
+    (a, b) => Err(format!("write-file expected 2 strings, got: {:?} {:?}", a, b)),
+  }
+}
diff --git a/src/builtins/meta.rs b/src/builtins/meta.rs
index b37f7e41..86443f50 100644
--- a/src/builtins/meta.rs
+++ b/src/builtins/meta.rs
@@ -41,7 +41,7 @@ pub fn recur(xs: &CalcitItems) -> Result<Calcit, String> {
 
 pub fn format_to_lisp(xs: &CalcitItems) -> Result<Calcit, String> {
   match xs.get(0) {
-    Some(v) => Ok(Calcit::Str(primes::format_to_lisp(v))),
+    Some(v) => Ok(Calcit::Str(v.lisp_str())),
     None => Err(String::from("format-to-lisp expected 1 argument")),
   }
 }
diff --git a/src/builtins/refs.rs b/src/builtins/refs.rs
index 23539c86..8144b0c2 100644
--- a/src/builtins/refs.rs
+++ b/src/builtins/refs.rs
@@ -74,4 +74,11 @@ pub fn reset_bang(xs: &CalcitItems) -> Result<Calcit, String> {
   }
 }
 
-// TODO add-watch remove-watch
+// TODO
+pub fn add_watch(_xs: &CalcitItems) -> Result<Calcit, String> {
+  Ok(Calcit::Nil)
+}
+// TODO
+pub fn remove_watch(_xs: &CalcitItems) -> Result<Calcit, String> {
+  Ok(Calcit::Nil)
+}
diff --git a/src/builtins/strings.rs b/src/builtins/strings.rs
index fc4a0f44..08523b05 100644
--- a/src/builtins/strings.rs
+++ b/src/builtins/strings.rs
@@ -204,3 +204,16 @@ pub fn blank_ques(xs: &CalcitItems) -> Result<Calcit, String> {
     None => Err(String::from("blank? expected 1 argument, got nothing")),
   }
 }
+
+pub fn escape(xs: &CalcitItems) -> Result<Calcit, String> {
+  match xs.get(0) {
+    Some(Calcit::Str(s)) => {
+      let mut chunk = String::from("\"");
+      chunk.push_str(&s.escape_default().to_string());
+      chunk.push('"');
+      Ok(Calcit::Str(chunk))
+    }
+    Some(a) => Err(format!("escape expected 1 string, got {}", a)),
+    None => Err(String::from("escape expected 1 argument, got nothing")),
+  }
+}
diff --git a/src/call_stack.rs b/src/call_stack.rs
index f878e119..67e1c52c 100644
--- a/src/call_stack.rs
+++ b/src/call_stack.rs
@@ -56,6 +56,11 @@ pub fn show_stack() {
   }
 }
 
+pub fn clear_stack() {
+  let stack = &mut CALL_STACK.lock().unwrap();
+  stack.clear();
+}
+
 pub fn display_stack(failure: &str) {
   let stack: &Vec<CalcitStack> = &mut CALL_STACK.lock().unwrap();
   println!("\ncall stack:");
diff --git a/src/cirru/calcit-core.cirru b/src/cirru/calcit-core.cirru
index c45bb819..74f4ce09 100644
--- a/src/cirru/calcit-core.cirru
+++ b/src/cirru/calcit-core.cirru
@@ -315,7 +315,7 @@
 
         |&case $ quote
           defmacro &case (item default pattern & others)
-            assert "|expects pattern in a pair"
+            assert "|`case` expects pattern in a pair"
               if (list? pattern) (&= 2 (count pattern)) false
             let
                 x $ first pattern
@@ -817,7 +817,7 @@
                     &let nil
                       echo "|Failed assertion:" (quote ~xs)
                       raise
-                        ~ $ &str-concat (&str-concat message "| ") xs
+                        ~ $ &str-concat (&str-concat message "| ") (format-to-lisp xs)
 
         |join-str $ quote
           defn join-str (xs0 sep)
diff --git a/src/cli_args.rs b/src/cli_args.rs
index 3a05c46b..28ab97d7 100644
--- a/src/cli_args.rs
+++ b/src/cli_args.rs
@@ -1,8 +1,8 @@
-use crate::primes;
+pub const CALCIT_VERSION: &str = "0.3.0-a9";
 
 pub fn parse_cli<'a>() -> clap::ArgMatches<'a> {
   clap::App::new("Calcit Runner")
-    .version(primes::CALCI_VERSION)
+    .version(CALCIT_VERSION)
     .author("Jon. <jiyinyiyong@gmail.com>")
     .about("Calcit Runner")
     .arg(
diff --git a/src/codegen/emit_js.rs b/src/codegen/emit_js.rs
index 885fbc7f..bb83e7f8 100644
--- a/src/codegen/emit_js.rs
+++ b/src/codegen/emit_js.rs
@@ -9,7 +9,7 @@ use std::path::Path;
 use crate::builtins::meta::{js_gensym, reset_js_gensym_index};
 use crate::builtins::{is_proc_name, is_syntax_name};
 use crate::primes;
-use crate::primes::{format_to_lisp, Calcit, CalcitItems, SymbolResolved::*};
+use crate::primes::{Calcit, CalcitItems, SymbolResolved::*};
 use crate::program;
 use crate::util::string::has_ns_part;
 use crate::util::string::{matches_js_var, wrap_js_str};
@@ -308,7 +308,7 @@ fn gen_call_code(
         },
 
         "defmacro" => Ok(format!("/* Unexpected macro {} */", xs)),
-        "quote-replace" | "quasiquote" => Ok(format!("(/* Unexpected quasiquote {} */ null)", format_to_lisp(xs))),
+        "quote-replace" | "quasiquote" => Ok(format!("(/* Unexpected quasiquote {} */ null)", xs.lisp_str())),
 
         "raise" => {
           // not core syntax, but treat as macro for better debugging experience
@@ -546,7 +546,7 @@ fn gen_let_code(
   // break unless nested &let is found
   loop {
     if let_def_body.len() <= 1 {
-      return Err(format!("Unexpected empty content in let, {:?}", xs));
+      return Err(format!("unexpected empty content in let, {:?}", xs));
     }
     let pair = let_def_body[0].clone();
     let content = let_def_body.skip(1);
diff --git a/src/main.rs b/src/main.rs
index dc31dfd3..adb4db67 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -32,6 +32,8 @@ fn main() -> Result<(), String> {
 
   let mut eval_once = cli_matches.is_present("once");
 
+  println!("calcit_runner version: {}", cli_args::CALCIT_VERSION);
+
   // load core libs
   let bytes = include_bytes!("./cirru/calcit-core.cirru");
   let core_content = String::from_utf8_lossy(bytes).to_string();
@@ -85,10 +87,22 @@ fn main() -> Result<(), String> {
     None => "js-out".to_owned(),
   };
 
-  if cli_matches.is_present("emit-js") {
-    run_codegen(&init_fn, &reload_fn, &program_code, &emit_path)?;
+  let task = if cli_matches.is_present("emit-js") {
+    run_codegen(&init_fn, &reload_fn, &program_code, &emit_path)
+  } else {
+    run_program(&init_fn, &reload_fn, &program_code)
+  };
+
+  if eval_once {
+    task?;
   } else {
-    run_program(&init_fn, &reload_fn, &program_code)?;
+    // error are only printed in watch mode
+    match task {
+      Ok(_) => {}
+      Err(e) => {
+        println!("\nfailed to run, {}", e);
+      }
+    }
   }
 
   if !eval_once {
@@ -111,6 +125,7 @@ fn main() -> Result<(), String> {
               }
               notify::DebouncedEvent::Write(_) => {
                 println!("\n-------- file change --------\n");
+                call_stack::clear_stack();
 
                 // Steps:
                 // 1. load changes file, and patch to program_code
diff --git a/src/primes.rs b/src/primes.rs
index 193965c1..704cfbe7 100644
--- a/src/primes.rs
+++ b/src/primes.rs
@@ -410,8 +410,6 @@ impl PartialEq for Calcit {
 pub const CORE_NS: &str = "calcit.core";
 pub const GENERATED_NS: &str = "calcit.gen";
 
-pub const CALCI_VERSION: &str = "0.3.0-a8";
-
 impl Calcit {
   pub fn turn_string(&self) -> String {
     match self {
@@ -419,4 +417,8 @@ impl Calcit {
       _ => format!("{}", self),
     }
   }
+
+  pub fn lisp_str(&self) -> String {
+    format_to_lisp(self)
+  }
 }
diff --git a/src/runner.rs b/src/runner.rs
index aef924cd..1f1f294e 100644
--- a/src/runner.rs
+++ b/src/runner.rs
@@ -14,7 +14,7 @@ pub fn evaluate_expr(
   file_ns: &str,
   program_code: &program::ProgramCodeData,
 ) -> Result<Calcit, String> {
-  // println!("eval code: {}", primes::format_to_lisp(expr));
+  // println!("eval code: {}", expr.lisp_str());
 
   match expr {
     Calcit::Nil => Ok(expr.clone()),
@@ -33,7 +33,7 @@ pub fn evaluate_expr(
     Calcit::List(xs) => match xs.get(0) {
       None => Err(format!("cannot evaluate empty expr: {}", expr)),
       Some(x) => {
-        // println!("eval expr: {}", primes::format_to_lisp(expr));
+        // println!("eval expr: {}", expr.lisp_str());
         // println!("eval expr: {}", x);
 
         let mut added_stack = false;
@@ -64,7 +64,7 @@ pub fn evaluate_expr(
 
             // TODO moving to preprocess
             let mut current_values = rest_nodes.clone();
-            // println!("eval macro: {} {}", x, primes::format_to_lisp(expr));
+            // println!("eval macro: {} {}", x, expr.lisp_str()));
             // println!("macro... {} {}", x, CrListWrap(current_values.clone()));
 
             push_call_stack(file_ns, &name, StackKind::Macro, &Some(expr.clone()), &rest_nodes);
@@ -79,7 +79,7 @@ pub fn evaluate_expr(
                   current_values = ys;
                 }
                 _ => {
-                  // println!("gen code: {} {}", x, primes::format_to_lisp(&code));
+                  // println!("gen code: {} {}", x, &code.lisp_str()));
                   break evaluate_expr(&code, scope, file_ns, program_code)?;
                 }
               }
diff --git a/src/runner/preprocess.rs b/src/runner/preprocess.rs
index e83d8fbc..dd7cae26 100644
--- a/src/runner/preprocess.rs
+++ b/src/runner/preprocess.rs
@@ -220,7 +220,7 @@ fn process_list_call(
             current_values = ys;
           }
           _ => {
-            // println!("gen code: {} {}", code, primes::format_to_lisp(&code));
+            // println!("gen code: {} {}", code, &code.lisp_str());
             let (final_code, v) = preprocess_expr(&code, scope_defs, file_ns, program_code)?;
             pop_call_stack();
             return Ok((final_code, v));