Question

In the code below, LETTERS and letters are global, or in the global search path and reachable through another package (same thing!)

> LETTERS
 [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S"
[20] "T" "U" "V" "W" "X" "Y" "Z"
> letters
 [1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "r" "s"
[20] "t" "u" "v" "w" "x" "y" "z"
> ls()
character(0)
> a <- "1 2 3"
> ls()
[1] "a"
> rm(a)
> ls()
character(0)
> 

Answer 1

For the same reason it doesn’t list all the exported functions in all the attached packages (from ?ls):

By default, the environment of the call to ‘ls’ or ‘objects’ is used.

Specify the environment that contains LETTERS and ls will print it’s name.

# LETTERS is in there somewhere...
sapply(search(),ls)