hansen(_at_)pegasus(_dot_)att(_dot_)com writes:
I personally don't have a problem with the lookahead. That's what seek()'s
are for, and in practice, you'll never have 35 megabytes of whitespace
before the potential non-whitespace octet.
You can't always seek(). If the grammar can't reasonably be parsed in
a single pass, there's something seriously wrong with it.
When dealing with binary objects, pretty much anything can happen in
practice. Regardless of whether or not something can happen in
practice, if something is legal, a parser has to correctly parse it or
it's not conforming.
1341 prohibited boundaries from being substrings of enclosing
boundaries. Many parsers developed to 1341 will make mincemeat of
objects that violate that prohibition. The prohibition was
inadvertantly removed in 1521--whoever did the grammar in 1521
seriously botched the job, it has a number of problems with it which
I've previously pointed out.
There is no pressing need to allow boundaries to be substrings of
enclosing boundaries. Composers can simply choose different
boundaries. Making parsers that can deal with both subsring
boundaries and trailing white space, on the other hand, is a complex
task.
--
_.John G. Myers Internet: jgm+(_at_)CMU(_dot_)EDU
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