XOR-trick and PUZZLE (was comma-operator)

McFarland clay at oravax.UUCP
Sat Jan 30 05:39:22 AEST 1988

In article <cVyaqyy00jaBF6M0=4 at andrew.cmu.edu> bader+ at andrew.cmu.edu (Miles Bader) writes:
>> How can you use the XOR trick to keep a doubly linked list, using only
>> one field for in each record, to code for finding both the following and 
>> the previous record?  
>To make it a bit clearer, you have to be able to find the NEXT record
>given the current and previous records, and find the PREVIOUS record
>given the current and the next record.

To make it a bit clearer all you have to do is XOR it with itself :-}

Of more interest, since you can store n things in a register and get
any of them back given the other n-1 you can store 
NEXT ^ PREVIOUS ^ KEY and keep the KGB from deciphering your linked
lists (Now where did I put that key...).

Clay Brooke-McFarland		    Odyssey Research Associates

"Wait! There's something we're all overlooking!" Chorus: "What|
is it, Doctor?" "I don't know. I'm overlooking it myself."    |

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