# Class type Pxp_tree_parser.index

    class type [< clone : 'a; node : 'a Pxp_document.node;
           set_node : 'a Pxp_document.node -> unit; .. >
         as 'a] index = object .. end

The type of indexes over the ID attributes of the elements. This type is the minimum requirement needed by the parser to create such an index.

    method add : string -> 'a Pxp_document.node -> unit

Add the passed node to the index. If there is already an ID with the passed string value, the exception `Pxp_tree_parser.ID_not_unique` can be raised. However, index implementations are free to also accept several identical IDs, although this does not comply to the standard.

    method find : string -> 'a Pxp_document.node

Finds the node with the passed ID value, or raises `Not_found`