Hi Sander,

Thanks for replying. That explains why I have always had problems with Shortest[…] as applied to strings. The Overlaps options also gives me results that I do not expect.

I'll try your fix. I never would have thought of straddling the pattern with

___

Another approach that works is to first split the main string using <f> and </f> as delimiters. Looks like I will be changing a lot of my code.

Thanks again,

Gregory

Hi Gregory,

This is a common pitfall of Shortest, as it does not get the Shortest expressions when used with Strings.

StringCases[text, ___ ~~ y : Shortest["<FILER>" ~~ ___ ~~ id ~~ ___ ~~ "</FILER>"] ~~ ___ :>y]

That does work. Sometimes one needs to specify and Except[...] inside as well.

The problem is that strings are matched in a certain way from left to right such that:

StringCases["<f>test</f><f>WWW</f><f>test</f>",  Shortest["<f>" ~~ ___ ~~ "WWW" ~~ ___ ~~ "</f>"]]

will return

"<f>test</f><f>WWW</f>"

not

"<f>WWW</f>"

If you really want to know why you have to read the PCRE documentation as (as far as I know) the Wolfram-patterns are converted to PCRE and then that library is used for matching.