range search syntax with xapian ?

hey ,

am looking for xapian syntax to do a range search

in my code i have

  class Table < AR
    acts_as_xapian :texts => [:title],
                                :values => [[ :left, 0, "left", :number
],[ :right, 1, "right", :number ] ],
                               :terms => [ [: left, 'L',
"left"],[:right, 'R', "right"]]
   end

and when a launch the following search in console i have an execption

  ActsAsXapian::Search.new([Table], 'left:1..100 AND right:30..200',
:limit => 100000).result

exception :

RuntimeError: QueryParserError: Unknown range operation
from
/Users/mecharek/tm/vendor/plugins/acts_as_xapian/lib/acts_as_xapian.rb:367:in
`parse_query'
from
/Users/mecharek/tm/vendor/plugins/acts_as_xapian/lib/acts_as_xapian.rb:367:in
`initialize'
from (irb):3:in `new'

i need help please

thx