One more thing about lab 3....
When you are done reading a document using yylex(), you'll have to
call yyrestart(file), where file is the standard I/O file pointer,
before you seek() the next document in the document database.
yyrestart() puts lex into its default state, discards any input
text that has been buffered, and arranges the lexer so it can
can start reading the new input.
Todd