gsub: replacing a.*a if no occurence of b in .*

All these methods do assume that you don't have nested <tag>'s, like so:

<tag><tag>foo</tag>useful stuff</tag>some garbage</tag>

For that you would really need a true parser. So I would double-check
to make sure this doesn't happen.

Do you have any control on where those XML files are generated
though? It sounds to me it might be easier to fix the utility
generating those XML files, since it clearly is doing something wrong.

On Feb 24, 2007, at 11:07 AM, Gabor Grothendieck wrote:

I assume <tag> is known.

This removes any occurrence </tag>.*</tag> where .* does not
contain <tag> or </tag>.

The regular expression, re, matches </tag>, then does a greedy
match (?U) for anything followed by </tag> but uses a zero
width lookahead subexpression (?=...) for the second </tag>
so that it it can be rematched again.  gsubfn in package
gsubfn is like the usual gsub except that instead of
replacing the match with a string it passes the match
to function f and then replaces the match with the output
of f.  See the gsubfn home page:
  http://code.google.com/p/gsubfn/
and vignette.

Haris Skiadas
Department of Mathematics and Computer Science
Hanover College