rand_seed: An unevaluated expression to return .Random.seed if exists
Description
This expression returns .Random.seed when
eval(rand_seed) and NULL otherwise.
Usage
rand_seed
Arguments
format
language { if (exists(".Random.seed", envir = globalenv())) ; get(".Random.seed", envir = globalenv()) }
Details
It is designed to work with
opts_knit$set(cache.extra = rand_seed) for
reproducibility of chunks that involve with random number
generation. See references.