Parser defines a "grammar"

Now we will build a parser. The parser specification that we create will define what the legal grammar is for the tokens it receives from the lexer. Here's the grammar for our book example:

books ::= book

books book

;

book ::= FIELD SLASH FIELD SLASH FIELD SLASH FIELD SLASH FIELD EOL

This grammar says: "books is comprised of either a book, or books followed

by book (note the recursive definition). A book is comprised of a FIELD

token followed by a SLASH token followed by 3 more FIELD/SLASH token

pairs, then finally a FIELD token followed by an EOL (End Of Line) token."

Now we will build a parser. The parser specification that we create will define what the legal grammar is for the tokens it receives from the lexer. Here's the grammar for our book example: