Hello,
Thanks to those who pointed out that my previous function p was not tail
recursive.
I think "exclude" (below) is. It seems to work on large files, although
on a 160K
file garbage collection fails to get enough space.
What I am trying to do is find, in input such as an HTML file, like
"ab<table>c",
the string before the keyword such as "table". So I try the keyword
parsers
(in the list "ps" below) at each point in the input, and add the
character to
my answer if all the parsers fail. Something like a Boyer-Moore string
search might
be used to, though that would add complexity. I couldn't find such an
algorithm
in any Hugs library.
---------------------------- program -----------------------------
import ParseLib
exclude ans parsers = P (\inp -> case inp of
[] -> [(reverse ans,"")]
(c:cs) -> case papply try inp of
[(_,remaining)] -> [(reverse ans,remaining)]
[] -> papply (exclude (c:ans) parsers)
cs
)
where try = commonSubstring >> foldr1 (+++) parsers
test = papply (exclude "" ps) "ab<table>c"
commonSubstring = string "<"
ps = [string "table>",string "/table>" ]
ww.hs
