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Re^3: Hamming Distance Between 2 Strings - Fast(est) Way?

by ZWcarp (Beadle)
on Jul 08, 2011 at 16:38 UTC ( #913387=note: print w/ replies, xml ) Need Help??


in reply to Re^2: Hamming Distance Between 2 Strings - Fast(est) Way?
in thread Hamming Distance Between 2 Strings - Fast(est) Way?

Sorry this is probably a really dumb question...but.. what is the ^ character doing in this subfunction? I know in regex it means match the first... and its used as a way to negate character class when between brackets...but I cant find its use like shown above.


Comment on Re^3: Hamming Distance Between 2 Strings - Fast(est) Way?
Re^4: Hamming Distance Between 2 Strings - Fast(est) Way?
by BrowserUk (Pope) on Jul 08, 2011 at 19:46 UTC

    ^ in this case is bitwise-OR.

    When you bitwise-OR two strings, where the bytes in the two strings are the same, the byte in the resultant string will be chr(0); when they are different, the results will be non-chr(0). This allows you to count the number of differences in two strings very quickly:

    $seq1 = 'ACGTACGTACGTACGT';; $seq2 = 'TCGATCGATCGATCGA';; print ( $seq1 ^ $seq2 );; print length( $seq1) - ( $seq1 ^ $seq2 ) =~ tr[\0][\0];; 8

    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority".
    In the absence of evidence, opinion is indistinguishable from prejudice.
Re^4: Hamming Distance Between 2 Strings - Fast(est) Way?
by Anonymous Monk on Jul 09, 2011 at 04:53 UTC

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