sawine@1: int_op                 = "is" [ "not" ] 
sawine@1:                          | ("greater" | "less") "than"
sawine@1: string_op              = "is" [ "not" ]
sawine@1: string_array_op        = "is" [ "not" ]
sawine@1:                          | [ "not" ] "in"
sawine@1: string_string_array_op = [ "not" ] "in"