Useless rules
Encyclopedia
In formal grammar
, useless rules are rules of symbol production which are unreachable or unproductive, that is, they are rules of production which can never be applied.
D is unreachable.
Formal grammar
A formal grammar is a set of formation rules for strings in a formal language. The rules describe how to form strings from the language's alphabet that are valid according to the language's syntax...
, useless rules are rules of symbol production which are unreachable or unproductive, that is, they are rules of production which can never be applied.
Examples
D is unreachable.