Some enhancements for `dput()` with integer vectors

dput-int-string.R

dput_int_string <- function(x) {
  x <- sort(unique(as.integer(x)))
  d <- diff(x) == 1

  if (length(x) == 1 || all(d)) {
    return(utils::capture.output(dput(x)))
  }

  d[!d] <- NA
  d <- c(d, NA)
  len <- rle(d)$lengths
  end <- cumsum(len)[len > 1] + 1
  start <- end - len[len > 1]

  singles <- setdiff(seq_along(x), unlist(mapply(seq.int, start, end)))
  ind <- sort(c(singles, start))
  res <- paste0((x[ind]), "L")
  res[match(start, ind)] <- paste(x[start], x[end], sep = ":")
  paste0("c(", paste0(res, collapse = ", "), ")")
}

stopifnot(
  dput_int_string(c(0, 2, 6:8, 10, 12:20)) == "c(0L, 2L, 6:8, 10L, 12:20)"
)