Grammar Editor allows you to compose and use a context-free grammar. Write your grammar in the ``Grammar:'' text area. For example, you might type the following into the blank.

S -> A | B
A -> a A |
B -> b B |
Each symbol (nonterminals) should be in all capital letters; atoms (terminals) can be any combination of letters and digits, as long as they're not all capital letters. The symbol on the first rule's left side is assumed to be the root symbol in the grammar.

At the bottom of the window are three buttons.

Other topics:

Grammar syntax