Well, because it's late and I'm addicted, here's a regex to do it: 
sub rx_bits {
  my $str = shift;
  my $l = 0;
  $str =~ (
    "^" . join "", map "[01]" x ($_ - ($l+0,$l=$_)[0] - 2) . "(?:01|10
+)", @_
  );
}

[download]
I don't say it's fast, it's just a regex.
_____________________________________________________
Jeff[japhy]Pinyan: Perl, regex, and perl hacker, who'd like a job (NYC-area)
s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;

In reply to Re: fast bit twiddling by japhy
in thread fast bit twiddling by spurperl

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