   is_statement:         -> false
   is_pure_statement:    -> false
   top_sensitive:        -> false
-  operation_sensitive:  -> false
 
 #### Expressions
 

    @properties.push(prop)
    @children.push(prop)
    this

  operation_sensitive: ->
    true

  has_properties: ->
    !!@properties.length

  compile: (o) ->
    @options: merge o or {}
    @tab:     o.indent
    del @options, 'operation' unless this instanceof ValueNode
    top:      if @top_sensitive() then @options.top else del @options, 'top'
    closure:  @is_statement() and not @is_pure_statement() and not top and
              not @options.returns and not (this instanceof CommentNode) and
