diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -19,6 +19,7 @@
   - Microsoft SmallBasic parser: https://github.com/kwanghoon/sbparser
   - Polyrmorphic RPC calculus parser: https://github.com/kwanghoon/polyrpc
   - C11 parser: https://github.com/kwanghoon/c11parser
+  - EOPL interpreters: https://github.com/kwanghoon/Lecture_EOPL_Exercise (Its solution Lecture_EOPL also available in private)
 
 ### Download, build, and test
 ~~~
diff --git a/src/parserlib/AutomatonType.hs b/src/parserlib/AutomatonType.hs
--- a/src/parserlib/AutomatonType.hs
+++ b/src/parserlib/AutomatonType.hs
@@ -6,3 +6,11 @@
 type GotoTable   = [((Int, String), Int)]    -- key: (Int,String), value: Int
 type ProdRules   = [(String, [String])]      -- key: Int,          value: (String, [String])
 
+prProdRule :: (String, [String]) -> String
+prProdRule (x,ys) =  x ++ " -> "  ++ pr_ys ys
+  where
+    pr_ys []     = ""  
+    pr_ys [y]    = y 
+    pr_ys (y:ys) = y ++ " " ++ pr_ys ys
+
+
diff --git a/src/parserlib/CommonParserUtil.hs b/src/parserlib/CommonParserUtil.hs
--- a/src/parserlib/CommonParserUtil.hs
+++ b/src/parserlib/CommonParserUtil.hs
@@ -629,7 +629,7 @@
 
             let prodrule = prodRules !! n in
 
-            debug flag ("\t" ++ show prodrule) $
+            debug flag ("\t" ++ prProdRule prodrule) $
 
             let builderFun = pFunList  !! n in
             let lhs        = fst prodrule in
diff --git a/yapb.cabal b/yapb.cabal
--- a/yapb.cabal
+++ b/yapb.cabal
@@ -1,13 +1,13 @@
 cabal-version: 1.12
 
--- This file has been generated from package.yaml by hpack version 0.34.4.
+-- This file has been generated from package.yaml by hpack version 0.35.0.
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: c133b635fac4f9781f13419abca45b81d467bdf36d792e8884b3a6225a28e571
+-- hash: 5a75606bf54164b0ec65ff2140d206d12e6f0515f43690ced0195352f13bab63
 
 name:           yapb
-version:        0.2.6
+version:        0.2.7
 synopsis:       Yet Another Parser Builder (YAPB)
 description:    A programmable LALR(1) parser builder system. Please see the README on GitHub at <https://github.com/kwanghoon/yapb#readme>
 category:       parser builder
@@ -15,7 +15,7 @@
 bug-reports:    https://github.com/kwanghoon/yapb/issues
 author:         Kwanghoon Choi
 maintainer:     lazyswamp@gmail.com
-copyright:      2020-2021 Kwanghoon Choi
+copyright:      2020-2022 Kwanghoon Choi
 license:        BSD3
 license-file:   LICENSE
 build-type:     Simple