 
       @buildError: (content)->
         @build(is_error: true)
+
+      @buildUnlessExpression: (content)->
+        if content instanceof @
+          content
+        else
+          @buildWithContent([content])
 
       initialize: (opts={})->
         defaults =


      display: ->
        @expression.display()
    class_mixer(Equation)

    class ExpressionComponent

      toString: ->
        "Exp(b: #{@base().toString()}, p: #{@power().toString()})"

      isPowerOpen: -> @power().isOpen()

    class_mixer(Exponentiation)

