Answer
Giving production rules in Backus–Naur form for an identifier
if it can consist of
a) one or more lowercase letters.
b) at least three but no more than six lowercase letters.
c) one to six uppercase or lowercase letters beginning
with an uppercase letter.
d) a lowercase letter, followed by a digit or an underscore,
followed by three or four alphanumeric characters
(lower or uppercase letters and digits).
Work Step by Step
a) (identifier) ::= (lcletter) | (identifier)(lcletter)
(lcletter) ::= a | b | c | · · · | z
b) (identifier) ::= (lcletter)(lcletter)(lcletter) | (lcletter)(lcletter)(lcletter)(lcletter) |
(lcletter)(lcletter)(lcletter)(lcletter)(lcletter) |
(lcletter)(lcletter)(lcletter)(lcletter)(lcletter)(lcletter)
(lcletter) ::= a | b | c | · · · | z
c) (lcletter) ::=(lcletter) | (lcletter)(letter) | (ucletter)(letter)(letter) |
(ucletter)(letter)(letter)(letter) |
(ucletter) (letter)(letter)(letter)(letter) |
(ucletter)(letter)(letter)(letter)(letter)(letter)
(letter) ::= (lcletter) | (ucletter)
(lcletter) ::= a | b | c | · · · | z
(ucletter) ::= A | B | C | · · · | Z
d) (identifier) ::= (lcletter)(digitorus)(alphanumeric))(alphanumeric)(alphanumeric) |
(lcletter)(digitorus)(alphanumeric)(alphanumeric)(alphanumeric)
(letter) ::= (lcletter) | (ucletter)
(lcletter) ::= a | b | c | · · · | z
(ucletter) ::= A | B | C | · · · | Z
(digit) ::= 0 | 1 | 2 | · · · | 9
