Dear all:

I have IntegerList which has different numeric index. in particular, I am trying to figure out how to detect and replace  0 index in IntergerList with integer(0). How can I make this sort of manipulation efficiently? Does anyone knows any trick of doing this? 

This is different in R, and I am expecting latter:

> length(0)
[1] 1
> length(integer(0))
[1] 0

# data

foo <- list(
  idx1 <- IntegerList(1,2,3,0,4,0,0,6),
  idx2 <- IntegerList(1,1,1,2,0,3,4,0),
  idx3 <- IntegerList(1,2,4,4,5,0,6,7)
)

My idea is find out way to detect zero index in IntegerList, if I detect such index then it must be replaced with integer(0). I am trying to figure out which way I can detect zero index in very long IntegerList. This is my very first attempt to solve, but I bet there must have better way to solve it.

tmp <- lapply(foo, function(ele_) {
  res <- sapply(ele_, function(tt) {
    ans <- ifelse(is.na(tt), integer(0), tt)
  })
})

# my desired output

desired_list <- list(
  idx1_ <- IntegerList(1,2,3, integer(0), 4, integer(0), integer(0), 6),
  idx2_ <- IntegerList(1,1,1,2, integer(0), 3, 4, integer(0)),
  idx3_ <- IntegerList(1,2,4,4,5, integer(0), 6, 7)
)

How can I accomplish this easily/elegantly? Is there anyone give me possible idea for doing this? Thanks a lot

For a given IntegerList x, do:

x[all(x == 0L)] <- IntegerList(integer(0))