[antlr-interest] packrat vs. LL(*)
Steven Obua
steven at obua.de
Mon Jun 8 02:19:49 PDT 2009
Hi,
I am currently building a parser with ANTLR; I am really happy about
this great tool!
I found that the most convenient settings for my purposes are
backtrack=true
memoize=true
k=1
when leaving out the "k=1" option, antlr cannot process my grammar, it
runs into a timeout or something like that.
So, as I understand, with backtrack=true and memoize=true I basically
switch to linear time / linear space packrat parsing. If I accept the
constant slow down and the added space requirements, then it seems to
me that LL(*) parsing becomes superfluous. Shouldn't antlr therefore
maybe include a documented option "packrat" which implies the above
three option settings? I think packrat parsing is pretty popular, but
it took me about a day to figure out the exact settings I need to
make it happen in ANTLR.
Cheers,
Steven Obua
PS: USF rules!, have been an exchange student there for almost a year
about 10 years ago :-)
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