detectBadName <- function(name)
{
    !grepl("^[[:alpha:]]([[:alnum:]]|[_.])*$", name)
}

getType <- function(object)
{
    if (is.list(object))
    {
        paste0("+",
               if(is.data.frame(object)) "D"
               else if(isS4(object)) "S"
               else "L")
    } else
    {
        paste0(" ",
               if(is.function(object)) "f"
               else if(is.numeric(object)) "n"
               else if(is.character(object)) "c"
               else if(inherits(object, "formula")) "F"
               else if(is.logical(object)) "l")
    }
}

listObjects <- function()
{
    noms <- ls(envir = .GlobalEnv)
    objects <- mget(noms, envir = .GlobalEnv)
    types <- lapply(objects, getType)

    vars <- lapply(noms, function(nom)
    {
        if (detectBadName(nom))
        {
            nom <- gsub("\\n", "\\\\n", nom)
            nom <- gsub("\\t", "\\\\t", nom)
            nom <- gsub("\\`", "\\\\`", nom)
            paste0("`", nom, "`")
        } else nom
    })

    # if R-object-browser-fancy-char ?
    noms <- gsub("\\n", "⏎", noms)
    noms <- gsub("\\t", "⭾", noms)
    noms <- gsub("\\`", "\\\\`", noms)

    Map(cat, types, noms, vars, "\n") -> nul
}

listObjects()

objectContent <- function(x)
{
    if (is.list(x))
    {
        noms <- if (is.null(names(x))) 1:length(x) else names(x)
        objects <- mget(noms, envir = x)
        types <- lapply(objects, get_type)

        noms <- gsub("\\n", "⏎", noms)
        noms <- gsub("\\t", "⭾", noms)

        Map(cat, types, noms, "\n") -> nul
    }
}

object_content(irg)
object_content(irg[["data"]])
object_content(irg[["data"]][[1]])

search() "package:zzz"

list_packages <- function()
  printdfleft(data.frame(packages = gsub("^package:", "",
                                         Filter(function(x) grepl("^package:", x),
                                                search()))))

list_packages()

objects("package:zzz")
class("package::zzz")

objects("package:dplyr")

detach("package:zzz")
help("package:zzz")
help("zzz::fun")