relation inclusion operator

lib/active_relation/predicates.rb

@@ -40,15 +40,31 @@ module ActiveRelation
     end
   
     class GreaterThanOrEqualTo < Binary
+      protected
+      def predicate_sql
+        '>='
+      end
     end
   
     class GreaterThan < Binary
+      protected
+      def predicate_sql
+        '>'
+      end
     end
   
     class LessThanOrEqualTo < Binary
+      protected
+      def predicate_sql
+        '<='
+      end
     end
   
     class LessThan < Binary
+      protected
+      def predicate_sql
+        '<'
+      end
     end
   
     class Match < Base
@@ -69,6 +85,10 @@ module ActiveRelation
       def ==(other)
         super and attribute == other.attribute and relation == other.relation
       end
+      
+      def to_sql(options = {})
+        "#{attribute.to_sql} IN (#{relation.to_sql})"
+      end
     end
   end
 end

lib/active_relation/relations/order.rb

@@ -1,7 +1,7 @@
 module ActiveRelation
   module Relations
     class Order < Compound
-      attr_reader :relation, :orders
+      attr_reader :orders
   
       def initialize(relation, *orders)
         @relation, @orders = relation, orders

lib/active_relation/relations/projection.rb

@@ -1,14 +1,14 @@
 module ActiveRelation
   module Relations
     class Projection < Compound
-      attr_reader :relation, :attributes
+      attr_reader :attributes
   
       def initialize(relation, *attributes)
         @relation, @attributes = relation, attributes
       end
   
       def ==(other)
-        relation == other.relation and attributes == other.attributes
+        self.class == other.class and relation == other.relation and attributes == other.attributes
       end
   
       def qualify

lib/active_relation/relations/rename.rb

@@ -1,7 +1,7 @@
 module ActiveRelation
   module Relations
     class Rename < Compound
-      attr_reader :relation, :schmattribute, :alias
+      attr_reader :schmattribute, :alias
   
       def initialize(relation, renames)
         @schmattribute, @alias = renames.shift

lib/active_relation/relations/selection.rb

@@ -1,7 +1,7 @@
 module ActiveRelation
   module Relations
     class Selection < Compound
-      attr_reader :relation, :predicate
+      attr_reader :predicate
   
       def initialize(relation, *predicates)
         @predicate = predicates.shift