diff --git a/README.md b/README.md
index f3cbb32..74422c7 100644
--- a/README.md
+++ b/README.md
@@ -8,15 +8,17 @@ This project is a toy box for my dynamic language ideas.
 
 ## So Many Tasks
 
-- [ ] Refactorings
+- __Refactorings__
   - [ ] Make `is_a?` guards more elegant
   - [ ] Import test cases from Mal
   - [ ] Add CI
   - [ ] More OOP (`evaluator`)
-  - [ ] Use standard `readline` implementation
+  - [x] Use standard `readline` implementation
   - [ ] Better lexer and parser
   - [ ] Add examples
-- [ ] Add more language features using Crystal's semantics (e.g. union type)
+  - [ ] More convenient REPL (e.g. completion)
+- __New language features using Crystal's semantics__
+  - [ ] Algebraic data type
   - ...
 
 ## Installation
diff --git a/src/core.cr b/src/core.cr
index 637cd54..a5de839 100644
--- a/src/core.cr
+++ b/src/core.cr
@@ -1,10 +1,10 @@
 require "time"
+require "readline"
 
 require "./types"
 require "./error"
 require "./printer"
 require "./reader"
-require "./readline"
 
 module Crisp
 
@@ -274,7 +274,7 @@ end
 def self.readline(args)
   head = args.first.unwrap
   eval_error "1st argument of readline must be string" unless head.is_a? String
-  my_readline head
+  Readline.readline head
 end
 
 def self.meta(args)
diff --git a/src/crisp.cr b/src/crisp.cr
index edd6019..4a6b25c 100755
--- a/src/crisp.cr
+++ b/src/crisp.cr
@@ -1,8 +1,8 @@
 #! /usr/bin/env crystal run
 
 require "colorize"
+require "readline"
 
-require "./readline"
 require "./reader"
 require "./printer"
 require "./types"
@@ -269,7 +269,7 @@ unless ARGV.empty?
   exit
 end
 
-while line = my_readline("Crisp> ")
+while line = Readline.readline("Crisp> ", true)
   begin
     puts rep(line)
   rescue e
diff --git a/src/readline.cr b/src/readline.cr
deleted file mode 100644
index e57099a..0000000
--- a/src/readline.cr
+++ /dev/null
@@ -1,21 +0,0 @@
-# Note:
-# Crystal already has "readline" library.
-# I implemented a subset of it again for practice.
-
-@[Link("readline")]
-lib LibReadline
-  fun readline(prompt : UInt8*) : UInt8*
-  fun add_history(line : UInt8*)
-end
-
-def my_readline(prompt = "")
-  line = LibReadline.readline(prompt)
-  if line
-    LibReadline.add_history(line)
-    String.new(line)
-  else
-    nil
-  end
-ensure
-  LibC.free(line as Void*) if line
-end