own statements class for mom

so we don’t have to deal with arrays (as a special case)
and use method sending as is good oo

lib/mom/instruction.rb

@@ -17,20 +17,11 @@ module Mom
     end
   end
 
-  class Statement
-    # flattening will change the structure from a tree to a linked list (and use
-    # next_instruction to do so)
-    def flatten
-      raise "not implemented"
-    end
-  end
-
 end
 
 require_relative "simple_call"
-require_relative "if_statement"
-require_relative "while_statement"
 require_relative "truth_check"
 require_relative "jump"
 require_relative "slot_load"
 require_relative "return_sequence"
+require_relative "statement"

lib/mom/statement.rb

@@ -0,0 +1,21 @@
+module Mom
+  class Statement
+    # flattening will change the structure from a tree to a linked list (and use
+    # next_instruction to do so)
+    def flatten
+      raise "not implemented for #{self}"
+    end
+  end
+
+  class Statements < Statement
+    include Common::Statements
+
+    def flatten
+      @statements.each{ |s| s.flatten }
+    end
+  end
+
+end
+
+require_relative "if_statement"
+require_relative "while_statement"