/*
 *  call-seq:
 *     term_doc_enum.each_position {|pos| do_something } -> term_doc_enum
 *
 *  Iterate through each of the positions occupied by the current term in the
 *  current document. This can only be called once per document. It can be
 *  used within the each method. For example, to print the terms documents and
 *  positions;
 *
 *    tde.each do |doc_id, freq|
 *      puts "term appeared #{freq} times in document #{doc_id}:"
 *      positions = []
 *      tde.each_position {|pos| positions << pos}
 *      puts "  #{positions.join(', ')}"
 *    end
 */
static VALUE
frt_tde_each_position(VALUE self)
{
    TermDocEnum *tde = (TermDocEnum *)DATA_PTR(self);
    int pos;
    if (tde->next_position == NULL) {
        rb_raise(rb_eNotImpError, "to scan through positions you must create "
                 "the TermDocEnum with Index#term_positions method rather "
                 "than the Index#term_docs method");
    }
    while (0 <= (pos = tde->next_position(tde))) {
        rb_yield(INT2FIX(pos));
    }
    return self;
}