looping nested lists in R

Question

I have a huge nested list of 15 levels. i need to replace empty lists occurring at any level with chr "". I tried lapply to loop through the list but it's not working. is there any easy way to do this?

nested_list<-list(a=list(x=list(),y=list(i=list(),j=list(p=list(),q=list()))),b=list())

lapply(nested_list,function(x) if(length(x)==0) "" else x)

the lapply is being applied to only first level, how do i recursively loop the entire nested list and perform this action?

Answer 1

Try the following recursion.

foo <- function(l){
    lapply(l, function(x) if(length(x)==0) "" else foo(x))
}
foo(nested_list)

EDIT: A better version

foo <- function(l){
    lapply(l, function(x) if(is.list(x) && length(x)==0) "" else if(is.list(x)) foo(x) else x)
}