AST : abstract syntax tree (1a) an opening parenthesis, followed by (1b) zero or more list elements, followed by (1c) a

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AST : abstract syntax tree
(1a) an opening parenthesis, followed by
(1b) zero or more list elements, followed by
(1c) a closing parenthesis

where a list element is either

(2) a nanoL list (expression), or

(3) an alphanumeric "atom" (i.e., an identifier starting with a
letter)

nanoL ignores whitespace around its tokens (parentheses and
atoms).
1. Using the algebraic data type defined above
(NanoElement, NanoList, and NanoAtom), construct a specific AST
instance for the nanoL expression

( ( hello world ) ( what up ) )