MyRPL sets

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 SIZE -> 5

{a b c d e} ENTER 2 ENTER 3 ENTER SUB -> {b c}
"abcde" ENTER 2 ENTER 3 ENTER SUB -> "bc"