Experiments with the function rapply in R's base library

fun_w_rapply.R

library(magrittr)

str_replace_all <- function(text, pattern, replacement){
  gsub(pattern = pattern, replacement = replacement, x = text, perl = TRUE)
}

str_remove_all <- function(text, pattern){
  str_replace_all(text, pattern = pattern, replacement = "")
}

pretty_str <- function(x){
  capture.output(str(x)) %>% 
    str_replace_all("\\$ :", "~") %>%
    str_replace_all("\\.\\.", " ") %>%
    str_replace_all("([[:alpha:]]+)\\s*:\\s*(.+)", "\\1: \\2") %>% 
    str_replace_all("List of [1-9]+", "List:") %>% 
    str_remove_all(" chr|num ") %>%
    str_remove_all("\\$") %>%
    paste(collapse = "\n") %>% 
    cat()
}

my_list <- list(
  list(id = "a", 
       val = 2),
  list(id = "b", 
       val = 1, 
       children = list(
         list(id = "b1", 
              val = 2.5),
         list(id = "b2", 
              val = 8))))
# Double all numbers 
my_list %>% 
  rapply(function(x) x*2, classes = "numeric", how = "replace") %>% 
  pretty_str()
#> List:
#>  ~List:
#>     id: "a"
#>     val: 4
#>  ~List:
#>     id: "b"
#>     val: 2
#>     children: List:
#>      ~List:
#>         id: "b1"
#>         val: 5
#>      ~List:
#>         id: "b2"
#>         val: 16

# Get all characters out and squash to flat list
rapply(my_list, I, classes = "character", how = "unlist")
#>          id          id children.id children.id 
#>         "a"         "b"        "b1"        "b2"


my_list <- list(
  list(id = "hi", 
       attribs = list(
         class = "a")),
  list(id = "there", 
       attribs = list(
         class = "b"))
)

extract_chr <- function(x, ...){
  path_to_query <- paste(list(...), collapse = ".")
  flattened <- rapply(x, I, classes = "character", how = "unlist")
  flattened[names(flattened) == path_to_query]
}

extract_chr(my_list, "id")
#>      id      id 
#>    "hi" "there"
extract_chr(my_list, "attribs", "class")
#> attribs.class attribs.class 
#>           "a"           "b"