diff --git a/Gemfile b/Gemfile
index 5231162..09700ba 100644
--- a/Gemfile
+++ b/Gemfile
@@ -4,7 +4,7 @@ git_source(:github) {|repo_name| "https://github.com/#{repo_name}" }
 gem 'thor'
 gem 'rly'
 gem 'pry'
-
+gem 'opal'
 
 # Specify your gem's dependencies in mm2ep_depend.gemspec
 gemspec
diff --git a/lib/mm2ep_depend/parser.rb b/lib/mm2ep_depend/parser.rb
index dc36cf4..e5afbca 100755
--- a/lib/mm2ep_depend/parser.rb
+++ b/lib/mm2ep_depend/parser.rb
@@ -74,7 +74,7 @@ module Mm2ep
       end
 
       def to_s
-        "( #{@expr1.to_s}) AND (#{@expr2.to_s} )"
+        "( #{@expr1.to_s} ) AND ( #{@expr2.to_s} )"
       end
     end
 
@@ -89,7 +89,7 @@ module Mm2ep
       end
 
       def to_s
-        "( #{@expr1.to_s}) OR (#{@expr2.to_s} )"
+        "( #{@expr1.to_s} ) OR ( #{@expr2.to_s} )"
       end
     end
 
@@ -127,6 +127,7 @@ module Mm2ep
       precedence :left, 'OR_OP'
       precedence :left, 'AND_OP'
       precedence :left, 'EQ_OP'
+      precedence :left, 'L_PAR', 'R_PAR'
       precedence :right, :UMINUS
 
       rule 'statement : expr' do |st, e|