fragment <-previous: condition=[code] -> fragment
fragment <-next: condition=[code] -> fragmentReturn the next/previous fragment of the double linked fragment list for
which code succeeds. If code is omitted, these methods return the
next/previous fragment of the list. While executing the condition, @arg1
is bound the candidate fragment. Execution may not alter the
fragment list of the associated
fragment<-text_buffer.
If no fragment can be found in the indicated direction, these methods
fail.