'(#|'.b;module Scheme;T,R,I,C,K=Struct.new(:a,:d,:o){include Enumerable# |#)#|
def initialize x,y=(),o=0.!;super c(x),c(y),o;K.empty?&&(R.delete a;R.delete d
R<<self)end;def-@;T[:-,self]end;alias == equal?;def call i;Scheme.t self,i end
def to_a;[T[:*,self]]end;def c o;Array===o ?Scheme.l(o):o end;def each&b;b.(a)
d&&d.each(&b)end},[],e=Struct.new(:t,:u){def[]=k,v;t[k]=v end;def[]i;t.fetch(i
){u[i]}end},e[_h={}],[];def Object.const_missing i;i end;class::Fixnum;undef[]
def[]i;T[self,T[i],1]end end;          module A;def call *a;a.empty?? T[self]:
Scheme.t(self,a[0])end;def-@;           T[:-,T[self]] end end;class::Array;def
call a;T[self,T===a&&a.o ? a:            T[a],1]end end;class::Symbol;def*i;T[
self,T[:*,T[i]]]end;include A             ;def -i;Symbol===i ?:"#{self}-#{i}":
T[self,T[:-,T[i]]]end end;at_exit{        R.drop(K[0]=$0==__FILE__ ?0:2).each{
|l|v l}};B=TOPLEVEL_BINDING;class::        String;include A end;m=eval('self',
B);def m.method_missing i,*s;a,=s;s         .empty?? i:T[i,T===a&&a.o ? a:T[a]
] end;class<<self;def e f,n;f.map{          |i|v i,n}[-1]end;def r x,f,n;->*a{
e x.d.d,I[f ?Hash[f.zip a]:{},n]}             end; def l v;v.reverse.inject(()
){|a,i|T[i,a]}end;def t s,i;T[s,              Array===i ? T[i[0]]:T===i&&i.o ?
i:T[i],1]end;def v x,n=C; case                 x when T;case x.a when :LAMBDA;
r x,x.d.a,n when :LET;e={};x.                   d.a.each{|i|e[i.a]=v i.d.a,n};
e x.d.d,I[e,n]when :IF;v(v(x         .d.         a,n)?x.d.d.a: (y=x.d.d.d)?y.a
: (),n)when :DEFINE;Symbol.        ===(u=         x.d.a)?(n[u]=v x.d.d.a,n): (
n.[]=(u.a,r(x,u.d,n)))when        :QUOTE;d        =x.d.a;d==false ?:FALSE:(d==
true)?:TRUE:d when :COND         ; while x=               x.d; (break e x.a.d,
n if :ELSE== x.a.a||v(x         .a.a,n))end;              else f,*r=x.map {|i|
v i,n}; f.call(*r);end         when Symbol;n              .[] x else x end end
end;%w(CONS a,b T[a,b]        PAIR? o T===o -             *s s.inject:- LENGTH
l l.to_a.size APPLY f,*n,s f.(*(n+(s||[]).map.to_a)) SYMBOL? o Symbol===o READ
* t=""*1;begin;gets&&eval(t<<($_!=$/?$_:x),B);rescue(Object);retry;end MAP p,l
l(l.map(&p)) NUMBER? o Numeric===o STRING? o String===o NOT o 0.!.==o ERROR *s
fail(s*"\s") EOF-OBJECT? o o==() DISPLAY o puts(o) SET-CDR! p,o p.d=o SET-CAR!
p,o p.a=o NULL? o o==() EQ? a,b a.equal?b * *s s.inject:* MIN *s s.min LIST *s
l(s) CAR p p.a CDR p p.d).each_slice(3){|t|eval'_h[:"%s"]=->%s{%s}'%t}end;# |#

(DEFINE (FACT N) . (
  (IF (EQ? N . (1)) . (
      1 [* N . ((FACT (- N . (1))))]))))

(DISPLAY (FACT 6))