diff --git a/bin/ruby2gv b/bin/ruby2gv
index 15bc148..40ea36d 100755
--- a/bin/ruby2gv
+++ b/bin/ruby2gv
@@ -106,7 +106,7 @@ class Rb2Gv
 
   def parseFile( xFile, xFromFile = nil, xLib = nil )
 
-    if xFromFile.nil? == false
+    if xFromFile
       puts "Parse #{xFile} required in #{xFromFile} :" if DEBUG
     else
       puts "Parse #{xFile} :" if DEBUG
@@ -120,11 +120,11 @@ class Rb2Gv
       if lxLineMatch = REQUIRE.match( xLine )
         xRequiredLib = lxLineMatch[2].gsub( /\.(rb|so)$/, "" )
 
-        if @hxNodes.has_key?( xRequiredLib ) == false
+        if not @hxNodes.has_key?( xRequiredLib )
           puts "  + Node #{xRequiredLib}" if DEBUG
 
           xRequiredFile = getLibraryPath( xRequiredLib )
-          if xRequiredFile.nil? == false
+          if xRequiredFile
             unless @lxStops.include?(xRequiredLib)
               @hxNodes[xRequiredLib] = gv_newNode( xRequiredLib )
               parseFile( xRequiredFile, xFile, xRequiredLib )
diff --git a/lib/graphviz.rb b/lib/graphviz.rb
index 12af9fc..501ef22 100644
--- a/lib/graphviz.rb
+++ b/lib/graphviz.rb
@@ -131,7 +131,7 @@ def add_nodes(node_name, options = {})
   def get_node( xNodeName, &block )
     node = @hoNodes[xNodeName] || nil
 
-    yield( node ) if( block and node.nil? == false )
+    yield( node ) if( block and node )
 
     return node
   end
@@ -298,7 +298,7 @@ def add_graph( xGraphName = nil, hOpts = {}, &block )
   def get_graph( xGraphName, &block )
     graph = @hoGraphs[xGraphName] || nil
 
-    yield( graph ) if( block and graph.nil? == false )
+    yield( graph ) if( block and graph )
 
     return graph
   end
@@ -499,7 +499,7 @@ def output( hOpts = {} )
     end
     xDOTScript << "}"
 
-    if @oParentGraph.nil? == false
+    if @oParentGraph
       xDOTScript = "subgraph #{GraphViz.escape(@name, :unquote_empty => true)} {\n" << xDOTScript
 
       return( xDOTScript )
@@ -776,7 +776,7 @@ def self.options( hOpts )
   #
   def self.parse( xFile, hOpts = {}, &block )
     graph = Dot2Ruby::new( hOpts[:path], nil, nil ).eval( xFile )
-    yield( graph ) if( block and graph.nil? == false )
+    yield( graph ) if( block and graph )
     return graph
   end
 
@@ -790,7 +790,7 @@ def self.parse( xFile, hOpts = {}, &block )
   #
   def self.parse_string( str, hOpts = {}, &block )
     graph = Dot2Ruby::new( hOpts[:path], nil, nil ).eval_string( str )
-    yield( graph ) if( block and graph.nil? == false )
+    yield( graph ) if( block and graph )
     return graph
   end
 
diff --git a/lib/graphviz/attrs.rb b/lib/graphviz/attrs.rb
index b519b4d..92b881a 100644
--- a/lib/graphviz/attrs.rb
+++ b/lib/graphviz/attrs.rb
@@ -44,9 +44,6 @@ def []( key )
                self[k] = v
             end
          else
-            if @data.key?( key.to_s ) == false
-               nil
-            end
             @data[key.to_s]
          end
       end
@@ -66,12 +63,10 @@ def []=( key, value )
          rescue => e
             raise AttributeException, "Invalide value `#{value}` for attribute `#{key}` : #{e}"
          end
-         unless value.nil?
-            @data[key.to_s] = value
 
-            if @graphviz.nil? == false
-               @graphviz.set_position( @name, key.to_s, @data[key.to_s] )
-            end
+         if value
+           @data[key.to_s] = value
+           @graphviz.set_position( @name, key.to_s, @data[key.to_s] ) if @graphviz
          end
       end
    end
diff --git a/lib/graphviz/edge.rb b/lib/graphviz/edge.rb
index c51f8cb..dd9b256 100644
--- a/lib/graphviz/edge.rb
+++ b/lib/graphviz/edge.rb
@@ -45,7 +45,7 @@ def initialize( vNodeOne, vNodeTwo, parent_graph )
 
       # Return the node one as string (so with port if any)
       def node_one( with_port = true )
-         if @node_one_port.nil? or with_port == false
+         if not (@node_one_port and with_port)
             GraphViz.escape(@node_one_id)
          else
             GraphViz.escape(@node_one_id, :force => true) + ":#{@node_one_port}"
@@ -55,7 +55,7 @@ def node_one( with_port = true )
 
       # Return the node two as string (so with port if any)
       def node_two( with_port = true )
-         if @node_two_port.nil? or with_port == false
+         if not (@node_two_port and with_port)
             GraphViz.escape(@node_two_id)
          else
             GraphViz.escape(@node_two_id, :force => true) + ":#{@node_two_port}"
diff --git a/lib/graphviz/xml.rb b/lib/graphviz/xml.rb
index 118d3f5..27158ed 100644
--- a/lib/graphviz/xml.rb
+++ b/lib/graphviz/xml.rb
@@ -49,7 +49,7 @@ def initialize( xml_file, *options )
 	   @show_text = true
 	   @show_attributes = true
 
-      if options.nil? == false and options[0].nil? == false
+      if options and options[0]
         options[0].each do |xKey, xValue|
           case xKey.to_s
             when "text"
@@ -74,11 +74,11 @@ def parse_xml_node( xml_node ) #:nodoc:
       label = xml_node.name
       if xml_node.has_attributes? and @show_attributes
         label = "{ " + xml_node.name
-		
+
 		    xml_node.attributes.each do |xName, xValue|
 		      label << "| { #{xName} | #{xValue} } "
 		    end
-		
+
 		    label << "}"
 	    end
       @graph.add_nodes( local_node_name, "label" => label, "color" => "blue", "shape" => "record" )