1 files changed, 58 insertions, 0 deletions
diff --git a/lib/arel/engines/memory/predicates.rb b/lib/arel/engines/memory/predicates.rb
new file mode 100644
index 0000000000..3522ea3ffa
--- /dev/null
+++ b/lib/arel/engines/memory/predicates.rb
@@ -0,0 +1,58 @@
+module Arel
+  class Predicate
+    def or(other_predicate)
+      Or.new(self, other_predicate)
+    end
+
+    def and(other_predicate)
+      And.new(self, other_predicate)
+    end
+  end
+
+  class Binary < Predicate
+    def eval(row)
+      operand1.eval(row).send(operator, operand2.eval(row))
+    end
+  end
+
+  class CompoundPredicate < Binary
+    def to_sql(formatter = nil)
+      "(#{operand1.to_sql(formatter)} #{predicate_sql} #{operand2.to_sql(formatter)})"
+    end
+  end
+
+  class Or < CompoundPredicate
+    def predicate_sql; "OR" end
+  end
+
+  class And < CompoundPredicate
+    def predicate_sql; "AND" end
+  end
+
+  class Equality < Binary
+    def ==(other)
+      Equality === other and
+        ((operand1 == other.operand1 and operand2 == other.operand2) or
+         (operand1 == other.operand2 and operand2 == other.operand1))
+    end
+  end
+
+  class GreaterThanOrEqualTo < Binary
+  end
+
+  class GreaterThan < Binary
+  end
+
+  class LessThanOrEqualTo < Binary
+  end
+
+  class LessThan < Binary
+    def operator; :< end
+  end
+
+  class Match < Binary
+  end
+
+  class In < Binary
+  end
+end