Question

1. Consider the following BNF:

Y ::= W S F | S M F | S M

W ::= "d" | "j" | "f"

S ::= "m" | "a" | "y"

M ::= "y" | "n" | "u" | "g"

F ::= "p" | "o" | "n"  

1. Write two strings that are valid according to the BNF.
2. For each of your two strings, give two valid mutants of the string.
3. For each of your two strings, give two invalid mutants of the string.

Answer 1

Grammars describe both valid strings and invalid strings.

both types can be produced as mutants.

Mutant is a variations of valid string. mutants may be valid or invalid strings.

a) Two valid strings according to BNF :

dmp, my

b) For each of two strings, two valid mutants of the string :

dmo, dmn, mn, mu

c) For each of two strings, two invalid mutants of the string :

dmu, dma, mp, ma