Rename Attribute Not -> Inequality and add a Not predicate (complement)

4 files changed, 26 insertions, 9 deletions

diff --git a/lib/arel/algebra/attributes/attribute.rb b/lib/arel/algebra/attributes/attribute.rb
index 5689d69b02..0266b38db3 100644
--- a/lib/arel/algebra/attributes/attribute.rb
+++ b/lib/arel/algebra/attributes/attribute.rb
@@ -84,7 +84,7 @@ module Arel
     module Predications
       methods = {
         :eq => "Equality",
-        :not => "Not",
+        :noteq => "Inequality",
         :lt => "LessThan",
         :lteq => "LessThanOrEqualTo",
         :gt => "GreaterThan",
diff --git a/lib/arel/algebra/predicates.rb b/lib/arel/algebra/predicates.rb
index ea1f771abb..43606139b0 100644
--- a/lib/arel/algebra/predicates.rb
+++ b/lib/arel/algebra/predicates.rb
@@ -8,6 +8,10 @@ module Arel
       def and(other_predicate)
         And.new(self, other_predicate)
       end
+      
+      def not
+        Not.new(self)
+      end
     end
     
     class Grouped < Predicate
@@ -35,6 +39,11 @@ module Arel
         a2.inject({}) { |h,e| h[e] = a2.select { |i| i == e }.size; h }
       end
     end
+    
+    class Unary < Predicate
+      attributes :operand
+      deriving :initialize, :==
+    end
 
     class Binary < Predicate
       attributes :operand1, :operand2
@@ -59,7 +68,7 @@ module Arel
       end
     end
 
-    class Not                   < Equality; end
+    class Inequality            < Equality; end
     class GreaterThanOrEqualTo  < Binary;   end
     class GreaterThan           < Binary;   end
     class LessThanOrEqualTo     < Binary;   end
diff --git a/lib/arel/engines/memory/predicates.rb b/lib/arel/engines/memory/predicates.rb
index b8642136d8..d0963e2f74 100644
--- a/lib/arel/engines/memory/predicates.rb
+++ b/lib/arel/engines/memory/predicates.rb
@@ -10,7 +10,7 @@ module Arel
       def operator; :== end
     end
 
-    class Not < Equality
+    class Inequality < Equality
       def eval(row)
         operand1.eval(row) != operand2.eval(row)
       end
diff --git a/lib/arel/engines/sql/predicates.rb b/lib/arel/engines/sql/predicates.rb
index 7fac09e750..29bc74c605 100644
--- a/lib/arel/engines/sql/predicates.rb
+++ b/lib/arel/engines/sql/predicates.rb
@@ -5,6 +5,16 @@ module Arel
         "#{operand1.to_sql} #{predicate_sql} #{operand1.format(operand2)}"
       end
     end
+    
+    class Unary < Predicate
+      def to_sql(formatter = nil)
+        "#{predicate_sql} (#{operand.to_sql(formatter)})"
+      end
+    end
+    
+    class Not < Unary
+      def predicate_sql; "NOT" end
+    end
 
     class CompoundPredicate < Binary
       def to_sql(formatter = nil)
@@ -44,10 +54,8 @@ module Arel
       end
     end
 
-    class Not < Binary
-      def predicate_sql
-        operand2.not_predicate_sql
-      end
+    class Inequality < Equality
+      def predicate_sql; '!=' end
     end
 
     class GreaterThanOrEqualTo < Binary
@@ -75,11 +83,11 @@ module Arel
     end
 
     class In < Binary
-      def to_sql
+      def to_sql(formatter = nil)
         if operand2.is_a?(Range) && operand2.exclude_end?
           GreaterThanOrEqualTo.new(operand1, operand2.begin).and(
             LessThan.new(operand1, operand2.end)
-          ).to_sql
+          ).to_sql(formatter)
         else
           super
         end