In a formal grammar, an erasing rule is a rule which maps a string of symbols to the empty string (ε).
Formally, an erasing rule is an ε-production, like
Famous quotes containing the word rule:
“The daughter of debate, that eke discord doth sow,
Shall reap no gain where former rule hath taught still peace to
grow.
No foreign banished wight shall anchor in this port;
Our realm it brooks no stranger’s force, let them elsewhere resort.”
—Elizabeth I (1533–1603)