recursive memory operations now possible

Conflicts:

	lib/arel/algebra/relations/relation.rb

4 files changed, 22 insertions, 11 deletions

diff --git a/lib/arel/algebra/extensions/hash.rb b/lib/arel/algebra/extensions/hash.rb
index bc97785e62..7472b5aa73 100644
--- a/lib/arel/algebra/extensions/hash.rb
+++ b/lib/arel/algebra/extensions/hash.rb
@@ -4,11 +4,4 @@ class Hash
       bound.merge(key.bind(relation) => value.bind(relation))
     end
   end
-  
-  def slice(*attributes)
-    inject({}) do |cheese, (key, value)|
-      cheese[key] = value if attributes.include?(key)
-      cheese
-    end
-  end
 end
\ No newline at end of file
diff --git a/lib/arel/algebra/relations.rb b/lib/arel/algebra/relations.rb
index b75a31e5e3..94df5938fe 100644
--- a/lib/arel/algebra/relations.rb
+++ b/lib/arel/algebra/relations.rb
@@ -2,6 +2,7 @@ require 'arel/algebra/relations/relation'
 require 'arel/algebra/relations/utilities/compound'
 require 'arel/algebra/relations/utilities/nil'
 require 'arel/algebra/relations/utilities/externalization'
+require 'arel/algebra/relations/row'
 require 'arel/algebra/relations/writes'
 require 'arel/algebra/relations/operations/alias'
 require 'arel/algebra/relations/operations/group'
diff --git a/lib/arel/algebra/relations/relation.rb b/lib/arel/algebra/relations/relation.rb
index 6d76e66638..fe8cab4b02 100644
--- a/lib/arel/algebra/relations/relation.rb
+++ b/lib/arel/algebra/relations/relation.rb
@@ -14,10 +14,6 @@ module Arel
       self
     end
 
-    def root
-      self
-    end
-
     module Enumerable
       include ::Enumerable
 
diff --git a/lib/arel/algebra/relations/row.rb b/lib/arel/algebra/relations/row.rb
new file mode 100644
index 0000000000..2d63498452
--- /dev/null
+++ b/lib/arel/algebra/relations/row.rb
@@ -0,0 +1,21 @@
+module Arel
+  class Row
+    attributes :relation, :tuple
+    deriving :==, :initialize
+    
+    def [](attribute)
+      tuple[relation.position_of(attribute)]
+    end
+    
+    def slice(*attributes)
+      Row.new(relation, attributes.inject([]) do |cheese, attribute|
+        cheese << self[attribute]
+        cheese
+      end)
+    end
+    
+    def bind(relation)
+      Row.new(relation, tuple)
+    end
+  end
+end
\ No newline at end of file