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Question 1

What is recursion in BNF and when is it used?

Answer 1

Recursion is the referencing of a rule within the rule itself, allowing for infinite possibilities. Recursion should be used when both an unknown number, greater than 1 is required.

Question 2

Given the following BNF:

::= procedure ( )

::= | ;

::= : |
ref :

::= | ,

::= |

::= int | float | bool | char | string

Would the following inputs be valid?

1 - parameter - ref health, lives, points, deaths : int
2 - identifier - Michael1sth3b3st
3 - procedure-def - procedure 2ndlife(points:int,lives:int)

Answer 2

1 - Valid
2 - Invalid (contains numbers, which are no supported in the BNF given)
3 - Invalid (parameters should be delimited with a ; not a ,)