sub stest
{
    my $str = shift;
    my $last_index=1;
    my @sorted_indexes = sort { $a <=> $b } @_;
    die "bad index" if( $sorted_indexes[0] < 1 );
    
    my $offset;
    do {
    $last_index += ( 
        ( $offset = 
            ( (shift @sorted_indexes 
           || return true) 
          - $last_index
        ) || next 
        )
    );
    substr($str, 0, $offset, "");
    } while( $str=~/^01|^10/ );
    return false;
}

[download]
USE: stest( $bit_string, @indexes ) Should be ridiculously fast, because it takes every opportunity to jump out of the main loop as soon as the relevant data is available, and often before it is stored. There is no recursion, and extremely tiny memory footprint. The only potential bottleneck is that it requires the bit list to be sorted.

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

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.