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Postings from February 2009
David Nicol wrote:
>$ perl -lwe '$a="xyzt"x10000; utf8::upgrade($a);print $a =~
>/\A(?>(?>[a-z])*)*\z/ ? "ok" : "bug"'
>ok
The form you give here has very inefficient behaviour for a non-matching
string. Also, if the inner expression is more complex (e.g., (?>X?[a-z])
it generates the "recursion limit" warning. So it's better done as
/\A(?>(?>[a-z]){1,32766})*\z/
I considered this class of workaround. It works for non-backtracking
expressions, and effectively squares the iteration limit. It's a great
practical improvement, but still most unsatisfying that it still has
a limit that is smaller than achivable address spaces. One can apply
multiple layers of quantification to get a still higher iteration limit,
but then I don't know how many to do.
So, it's an option. I'm happier using this as a local hack than as a
public solution.
-zefram
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