Emacs has many features not all of which are available with the
default installation. Wisent parser generator is one such. It is a
lexer and parser generator (like flex and bison). Since emacs can
easily interface external programs, you can always use an
external lexer/parser with emacs. But sometimes using wisent is a
viable alternative. Unfortunately there isn't many good wisent
tutorials for the beginner. So I wrote this one.