Why is it `sample0` not `sample` inside `cv.glm`?

Question

I am going through the source code for cv.glm from boot. There is one line

s <- sample0(rep(1L:K, f), n)

I looked up sample0, but it doesn't exist. I believe it really means sample(). Why is it entered as sample0 here?

Answer 1

Have a look at:

boot:::sample0
#function (x, ...) 
#x[sample.int(length(x), ...)]
#<bytecode: 0xa2a30e4>
#<environment: namespace:boot>

This is an internal / non-exported function in the namespace of boot.