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:
“Great statesmen seem to direct and rule by a sort of power to put themselves in the place of the nation over which they are set, and may thus be said to possess the souls of poets at the same time they display the coarser sense and the more vulgar sagacity of practical men of business.”
—Woodrow Wilson (1856–1924)