Re: [Boost-users] [Regex] "Truly" incremental search?

From: Eugene M. Kim (gene_at_[hidden])
Date: 2008-02-11 21:08:31

Renato golin wrote:
> Eugene M. Kim wrote:
>   
>> I am looking for a way to feed the input bytes only once, in order to 
>> reduce the time complexity to approximately O(n).  Of course I will lose 
>> the ability to recover submatches, but the ability is unnecessary for 
>> this particular application that I am considering.  I cannot break the 
>> regex into two parts ("omg" and "wtf") either because it is specified as 
>> an input to the program.
>>     
>
> Hi,
>
> It may sound silly but what if you pre-process the input splitting it by 
> ".*" and do an AND match for all sub-strings?
>
> input = "omg.*wtf" => input[] = "omg", "wtf";
> return (regexp_match(input[0]) && regexp_match(input[1]));
>
> cheers,
> --renato
>
> PS: of course the code above is pseudo-code and of course you'll take as 
> many input parameters as available and not hard-coded like this.
That would work for simple cases where the two sub-patterns are 
separated by ".*", but fail for other non-trivial expressions such as 
"omg(bbq|cakes)*wtf", which the program must also be able to accept.  ;_;

Eugene