improve readability of output list of foreach loop - r

Question

I have a simple example of foreach nested loop below. How can I improve the readability of the result res?
Below is another example of nested for loop with more readable results, each element of list can be easily identified e.g. res_desired[["B"]][[3]]
library(foreach)
library(doFuture)
registerDoFuture()
plan(multicore, workers = 1)
# foreach loop
res <- foreach(a = c("A", "B", "C", "D")) %:%
foreach(b = 1:4) %do%
{
paste0(rep(a, b))
}
# for loop
res_desired <- list()
for(a in c("A", "B", "C", "D"))
{
for(b in 1:4)
{
res_desired[[a]][[b]] <- paste0(rep(a, b))
}
}

Answer 1

The .final may be useful. According to ?foreach
.final - function of one argument that is called to return final result.
With one more nested loop
res_1 <- foreach(a = c("A", "B", "C", "D"),
.final = function(x) setNames(x, c("A", "B", "C", "D"))) %:%
foreach(c = c("a", "b", "c"),
.final = function(x) setNames(x, c("a", "b", "c"))) %:%
foreach(b = 1:4) %do% {paste0(rep(a, b))}
-checking
> res_1[["B"]][["c"]][[2]]
[1] "B" "B"
similar to
res_desired_1 <- list()
for(a in c("A", "B", "C", "D")) {
for(c in c("a", "b", "c")) {
for(b in 1:4) {
res_desired_1[[a]][[c]][[b]] <- paste0(rep(a, b))
}
}
}
> res_desired_1[["B"]][["c"]][[2]]
[1] "B" "B"