This is somewhat a hack for getting a function to evaluate based on a lookup vector. If the function is not found, it returns NULL.
Examples
mean_1_to_10 <- dr_func_eval("mean", v = c("mean", "sd"))(1:10)
x <- system.file("extdata/tso/sample705.fragment_length_hist.json.gz", package = "dracarys")
obj <- dr_func_eval("TsoFragmentLengthHistFile")$new(x)