On Thu, Aug 07, 2014 at 04:49:05PM +0000, seany via Digitalmars-d-learn wrote:
> On Thursday, 7 August 2014 at 16:12:59 UTC, Justin Whear wrote:
> >On Thu, 07 Aug 2014 16:05:16 +0000, seany wrote:
> >
> >>obviously there are ways like counting the match length, and then
> >>using the maximum length, instead of breaking as soon as a match is
> >>found.
> >>
> >>Are there any other better ways?
> >
> >You're not really using regexes properly. You want to greedily match
> >as much as possible in this case, e.g.:
> >
> >void main()
> >{
> > import std.regex;
> > auto re = regex("ab(cd)?");
> > assert("PREabcdPOST".matchFirst(re).hit == "abcd");
> > assert("PREabPOST".matchFirst(re).hit == "ab");
> >
> >}
>
> thing is, abcd is read from a file, and in the compile time, i dont
> know if cd may at all be there or not, ir if it should be ab(ef)
So basically you have a file containing regex patterns, and you want to
find the longest match among them?
One way to do this is to combine them at runtime:
string[] patterns = ... /* read from file, etc. */;
// Longer patterns match first
patterns.sort!((a,b) => a.length > b.length);
// Build regex
string regexStr = "%((%(%c%))%||%)".format(patterns);
auto re = regex(regexStr);
...
// Run matches against input
char[] input = ...;
auto m = input.match(re);
auto matchedString = m.captures[0];
T
--
When solving a problem, take care that you do not become part of the problem.
