Hi Folks,
Have you seen a data format like this: there is a pair of nested lists -- an
outerList that has an innerList. The lists can be repeated an arbitrary number
of times. There is no punctuation (separator) at the end of each outerList, but
there is punctuation at the end.
For example, suppose the data format consists of input data that is a series of
"A" characters and at the end is a "Z" character. Here are sample inputs:
Z
AZ
AAZ
AAAZ
AAAAZ
...
Here is a grammar for this:
------------------------------------------------------------
start: outerList 'Z'
outerList: /* empty */
| outerList outerListItem
outerListItem: innerList
innerList: /* empty */
| innerList innerListItem
innerListItem: 'A'
------------------------------------------------------------
So, this input:
AAAZ
could be due to one outerListItem and three innerListItems, or two
outerListItems and (0,3), (1,2), (2,1), or (3,0) innerListItems, or ...
It is my understanding that this is rare but does exist. A book that I am
reading says:
In practice, it's pretty rare to have a pair of nested
lists with no punctuation. It's confusing to parsers,
and it's confusing to humans, too.
Have you seen a data format like this?
/Roger
