Sometimes I think of my friends as a vector space over GF(2) where each entry defines what we have in common.
- email, phone and other providers
- clothing with more or less witty slogans
- discount cards for transport, food and culture
- (the fact that we have an) employer
- brand and operating system of our computers and phones
- number, kind and brand of our bicycles
- countries we've visited and lived in
- passion for lists