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by halma 3409 days ago
I remember this and other tricks are implemented in Gaigen (a code generator for geometric algebra).

https://sourceforge.net/projects/g25/?source=directory

The XOR trick is close to slide 16 of http://www.science.uva.nl/research/ias/ga/gaigen/files/20020...

...

How to compute the geometric product of unit orthogonal basis blades (3/3) If we represent each basis vector with a specific bit in a binary number (e1 = 001b, e2 = 010b, e3 = 100b), computing the geometric product of basis blades is exactly the xor operation on binary numbers!

  (e1^e2)(e2^e3) = e1^e3
  011b xor 110b = 101b
We have to take care of the signs though:

- basis vectors have to be rearranged into a specific order before they can annihilate each other (this rearranging causes a sign change in the result). This can also be computed binary. - signature of annihilated basis vectors can change the sign as well.