On Wed, May 6, 2009 at 3:11 AM, Eric Niebler
<eric@boostpro.com> wrote:
Eric Niebler wrote:
Lee Simpson wrote:
Hi,
First let me say. Awesome library and thanks for releasing it to the world.
Thanks!
I'm looking for a way to apply all the currently queued semantic actions _without_ turning off backtracking.
So, as the manual suggests, keep manages to apply the queued actions but it also turns off backtracking.
<snip>
Any ideas?
You don't have to turn off backtracking for the whole regex. You can use keep() in a few strategic places within your regex as follows:
sregex rx = ... >> keep(nil[ /*semantic action*/ ]) >> ...;
"nil" always succeeds and consumes 0 characters. It's a way to cause the semantic action to execute immediately. Would something like that help you?
#include <string>
#include <iostream>
#include <boost/xpressive/xpressive_static.hpp>
#include <boost/xpressive/regex_actions.hpp>
using namespace boost::xpressive;
int main()
{
std::string text = "abcd";
sregex rx =
// Match some stuff and save some submatches
(s1= +alpha) >> (s2= +alpha) >> eos >>
// Display the submatches eagerly.
keep(nil[ref(std::cout) << s1 << ", " << s2 << "\n"]) >>
// Cause the fail and backtrack.
~before(nil);
regex_match(text, rx);
return 0;
}
For me, this dispays:
abc, d
ab, cd
a, bcd
HTH,