diff --git a/lib/mm2ep_depend/lexer.rb b/lib/mm2ep_depend/lexer.rb
index d2c60dd..797c911 100755
--- a/lib/mm2ep_depend/lexer.rb
+++ b/lib/mm2ep_depend/lexer.rb
@@ -2,18 +2,18 @@ module Mm2ep
   module Depend
     class Lexer < Rly::Lex
 
+      token :SPACE, /\s+/
       token :L_PAR, /\(/
       token :R_PAR, /\)/
       token :NUMBER, /[0-9]+(\.[0-9]+)?/
       token :STRING, /"[^"]*"/
       token :EQ_OP, /\=/
-      token :T_BOOL, /[tT]rue/
-      token :F_BOOL, /[fF]alse/
+      token :T_BOOL, /true/i
+      token :F_BOOL, /false/i
       token :VAR, /[a-z][a-zA-Z0-9_]+/
       token :AND_OP, /AND/
       token :OR_OP, /OR/
       token :NOT_OP, /NOT/
-      token :SPACE, /\s+/
 
       on_error do |t|
         puts "Illegal character #{t.value}"
diff --git a/lib/mm2ep_depend/parser.rb b/lib/mm2ep_depend/parser.rb
index d24a108..6369ec9 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
 
@@ -103,7 +103,7 @@ module Mm2ep
       end
 
       def to_s 
-        "NOT (#{@expr.to_s})"
+        "NOT ( #{@expr.to_s} )"
       end 
     end
 
@@ -124,8 +124,10 @@ module Mm2ep
 
     class Parser < Rly::Yacc
 
-      precedence :left, 'OR_OP', 'EQ_OP'
-      precedence :left, 'AND_OP', 'NOT_OP'
+      precedence :left, 'OR_OP'
+      precedence :left, 'AND_OP'
+      precedence :left, 'EQ_OP' 
+      precedence :right, :UMINUS
 
       rule 'statement : expr' do |st, e|
         st.value = e.value
@@ -146,7 +148,7 @@ module Mm2ep
         ex.value = BoolValue.new(l.value.to_s)
       end
 
-      rule 'expr : NOT_OP SPACE expr' do |ex, l, s, e|
+      rule 'expr : NOT_OP SPACE expr %prec UMINUS' do |ex, l, s, e|
         ex.value = NotOp.new(e.value)
       end