Regex: workaround for variable length negative lookbehind

On Mon, Dec 1, 2008 at 12:20 AM, Wacek Kusnierczyk
<Waclaw.Marcin.Kusnierczyk at idi.ntnu.no> wrote:
  

Gabor Grothendieck wrote:
    

Try this:


      

vec <- c("aaaa", "baaa", "bbaa", "bbba", "baamm", "aa")

        

grep("^(?!(.)\\1{1,}$).*(.)\\2{1,}$", vec, perl = TRUE)

        

or even

grep("^(?!(.)\\1+$).*(.)\\2+$", vec, perl = TRUE)

    

Or combining the previous simplification I posted with yours:

  

grep("^(?!(.)\\1+$).*(.)\\2$", vec, perl = TRUE)