A set could be:
1) A list
2) A string
A list is a set of objects separated by blanks.
A string of characters is a set of characters.
Commands as HEAD, TAIL, GET , PUT , SIZE and SUB can be used in lists and strings
Examples:
(The meaning of -> is "see result at stack first level")
"abcde" ENTER HEAD -> "a"
"abcde" ENTER TAIL -> "bcde"
{ a b c d e } ENTER HEAD -> a
{ a b c d e } ENTER TAIL -> {b c d e}
{ a b c d e } ENTER 3 ENTER GET -> c
"abcde" ENTER 3 ENTER GET -> "c"
"abcde" ENTER 3 ENTER "h" PUT -> "abhde"
{a b c d e} ENTER 3 ENTER h PUT -> {a b h d e}
{a b c d e} ENTER SIZE -> 5
"abcde" ENTER SIZE -> 5
´
{a b c d e} ENTER 2 ENTER 3 ENTER SUB -> {b c}
"abcde" ENTER 2 ENTER 3 ENTER SUB -> "bc"
From version 1.12 the last ENTER is not necessary in all commands
Example:
Before version 1.12: "abcde" ENTER SIZE -> 5
Since 1.12: "abcde" SIZE -> 5