The Lemon program is an LALR(1) parser generator.  It takes a context free
grammar and converts it into a subroutine that will parse a file using that
grammar.

Lemon is similar to much more famous programs Yacc and Bison.  But lemon is
not compatible with either of them; there are several important differences:

  - Lemon using a different grammar syntax which is less prone to
    programming errors

  - Lemon generates a parser that is faster than Yacc or Bison parsers
    (according to the author)

  - The parser generated by Lemon is both re-entrant and thread-safe

  - Lemon includes the concept of a non-terminal destructor, which makes
    it much easier to write a parser that does not leak memory