Your Wish is My Command

12.3 Programming Grammars by Example for More Accessibility 231

l i eber@medi a.mi t. edu

and

nardi@appl e. com.

This pattern is expressed in BNF as a set of context-flee rules, each of which

tells the computer how to recognize a certain grammatical

category, or

nonterminal, as a sequence of specific strings, lexical categories such as

"Word" or "Number," or other nonterminals.

Below,

E - M a i 1 - A d d r e s s

is expressed in terms of

P e r s o n

and

H o s t.

We assume W o r d is a primitive token recognized by the parser.

<E-Mail-Address> := <Person> @ <Host>

<Person> := <Word>

<Host> := <Word> I <Word> ...