Re: Bug in Mathematica: regular expression applied to very

• To: mathgroup at smc.vnet.net
• Subject: [mg107492] Re: [mg107485] Bug in Mathematica: regular expression applied to very
• From: bsyehuda at gmail.com
• Date: Sun, 14 Feb 2010 08:17:26 -0500 (EST)
• References: <201002141059.FAA26040@smc.vnet.net>

```You can use the MAthematica string manipulation functions.
Let me lengthen the string in an obvious way, by duplicating it 1000 times.
s = "This is the first line.
MAGIC_STRING
Everything after this line should get removed.
12345678901234567890123456789012345678901234567890123456789012345678\
901234567890
12345678901234567890123456789012345678901234567890123456789012345678\
901234567890
12345678901234567890123456789012345678901234567890123456789012345678\
901234567890
12345678901234567890123456789012345678901234567890123456789012345678\
901234567890
12345678901234567890123456789012345678901234567890123456789012345678\
901234567890
...";

s = Nest[StringJoin[s, #] &, s, 1000];

StringLength[s]

492492

StringDrop[
StringReplace[
s, (p : Shortest[___ ~~ "\n" ~~ ___ ~~ "\n" ~~ ___ ~~
"\n"]) ~~ ___ :> p], -1]

so, processing only part of the string (using Shortest) gives the result in
a fraction of a second

yehuda

On Sun, Feb 14, 2010 at 12:59 PM, dreeves <dreeves at gmail.com> wrote:

> I believe I found a bug in Mathematica's regular expression engine:
>
> http://stackoverflow.com/questions/2257884/bug-in-mathematica-reg
>
> I've submitted a bug report to support@wolfram but also wondering if
> you all have thoughts on workarounds.
>
> Thanks!
>
> PS: Here's an rss feed of questions tagged mathematica on
> stackoverflow:
>  http://stackoverflow.com/feeds/tag?tagnames=mathematica
>
>

```

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