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:
“Man who man would be,
Must rule the empire of himself; in it
Must be supreme, establishing his throne
On vanquished will, quelling the anarchy
Of hopes and fears, being himself alone.”
—Percy Bysshe Shelley (1792–1822)