Many times a function will contain another function definition, these will not always be very readable in the body of the main function. {flow} offers a way to visualize those.
When using flow on the main function, a message will signify what nested functions can be viewed. The base function bquote is a good example.
library(flow)
flow_view(bquote)
#> We found function definitions in this code, use the argument nested_fun to inspect them
#> $unquote
#> function(e) {
#> if (is.pairlist(e))
#> as.pairlist(lapply(e, unquote))
#> else if (is.call(e)) {
#> if (is.name(e[[1L]]) && as.character(e[[1]]) == ".")
#> eval(e[[2L]], where)
#> else if (splice) {
#> if (is.name(e[[1L]]) && as.character(e[[1L]]) ==
#> "..")
#> stop("can only splice inside a call", call. = FALSE)
#> else as.call(unquote.list(e))
#> }
#> else as.call(lapply(e, unquote))
#> }
#> else e
#> }
#>
#> $is.splice.macro
#> function(e) is.call(e) && is.name(e[[1L]]) && as.character(e[[1L]]) ==
#> ".."
#>
#> $unquote.list
#> function(e) {
#> p <- Position(is.splice.macro, e, nomatch = NULL)
#> if (is.null(p))
#> lapply(e, unquote)
#> else {
#> n <- length(e)
#> head <- if (p == 1)
#> NULL
#> else e[1:(p - 1)]
#> tail <- if (p == n)
#> NULL
#> else e[(p + 1):n]
#> macro <- e[[p]]
#> mexp <- eval(macro[[2L]], where)
#> if (!is.vector(mexp) && !is.expression(mexp))
#> stop("can only splice vectors")
#> c(lapply(head, unquote), mexp, as.list(unquote.list(tail)))
#> }
#> }We can then inspect those by using the nested_fun argument, with a numeric id or a name (if unambiguous)
flow_view(bquote, nested_fun = "unquote")