Nothing
ulist <- list(u1, u2, u3, u4)
vlength <- function(x) sqrt(dot(x,x))
sapply(ulist, vlength)
c(dot(u1, u2), dot(u1, u3), dot(u1, u4),
dot(u2, u3), dot(u2, u4), dot(u3, u4))
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