Lisp in Ruby - { |one, step, back|

An oldie but a goodie: Jim Weirich’s Lisp 1.5 in Ruby

# Kernel Extensions to support Lisp class Object def lisp_string to_s end end class NilClass def lisp_string "nil" end end class Array # Convert an Array into an S-expression (i.e. linked list). # Subarrays are converted as well. def sexp result = nil reverse.each do |item| item = item.sexp if item.respond_to?(:sexp) result = cons(item, result) end result end end # The Basic Lisp Cons cell data structures. Cons cells consist of a # head and a tail. class Cons attr_reader :head, :tail def initialize(head, tail) @head, @tail = head, tail end def ==(other) return false unless other.class == Cons return true if self.object_id == other.object_id return car(self) == car(other) && cdr(self) == cdr(other) end # Convert the lisp expression to a string. def lisp_string e = self result = "(" while e if e.class != Cons result << ". " << e.lisp_string e = nil else result << car(e).lisp...

Full article: http://onestepback.org/index.cgi/Tech/Ruby/LispInRuby.red