The purpose of problem 2 is to construct the regular expression for the statement list based on the requirement in Q2.

You can use a symbol to denote dummy statement like '~'. I'll explain the question more clearly.

b; is a basic statement

l:b; is a basic statement with a label.

l:l:; is a dummy statement with two labels.


In Question 3 we have a example regular expression as
F = S (D* '.'? D+ | D+ '.'? D*) (S ('e' | 'E') D+)?
where S = '+' | '-' | empty and D = '0' | '1' ... '9'