Welcome to Racket v6.6.
> c0
c0: undefined;
 cannot reference undefined identifier
  context...:
   /usr/share/racket/collects/racket/private/misc.rkt:88:7
> c0
#<procedure:c0>
> (printn c0)
0
> (printn c50

)
c50: undefined;
 cannot reference undefined identifier
  context...:
   /usr/share/racket/collects/racket/private/misc.rkt:88:7
> (printn c5)
5
> (printn (cn 100))
100
> (printn (cs (cn 100)))
101
> (printn (c+ (cn 100) c5))
c+: arity mismatch;
 the expected number of arguments does not match the given number
  expected: 1
  given: 2
  arguments...:
   #<procedure:...box/numerals.scm:23:2>
   #<procedure:c5>
  context...:
   /usr/share/racket/collects/racket/private/misc.rkt:88:7
> (printn ((c+ (cn 100)) c5))
105
> (printn ((c* (cn 100)) c5))
500
> (printn ((c* (cn 100)) c5))
500
> (printn ((c++ (cn 100) c5)))
c++: arity mismatch;
 the expected number of arguments does not match the given number
  expected: 1
  given: 2
  arguments...:
   #<procedure:...box/numerals.scm:23:2>
   #<procedure:c5>
  context...:
   /usr/share/racket/collects/racket/private/misc.rkt:88:7
> (printn ((c++ (cn 100)) c5))
105
> (printn ((c** (cn 100)) c5))
#<procedure>
> (printn ((c** (cn 100)) c5))
500
> (printn ((c^^ (cn 10)) c5))
100000
> (printn ((c^ (cn 10)) c5))
100000
> (printn ((c1 c5) c5))
3125
> (printn (((cif c#t) c3) c5))
c3: undefined;
 cannot reference undefined identifier
  context...:
   /usr/share/racket/collects/racket/private/misc.rkt:88:7
> (printn (((cif c#t) c1) c5))
1
> (printn (((cif c#f) c1) c5))
5
> (printn (((cI c#t) c1) c5))
cI: undefined;
 cannot reference undefined identifier
  context...:
   /usr/share/racket/collects/racket/private/misc.rkt:88:7
> (printn (((I c#t) c1) c5))
1
> (printn (((I c#f) c1) c5))
5
> (printn ((c#t c1) c5))
1
> (printn ((c#f c1) c5))
5
> (printn (((c! c#f) c1) c5))
1
> (printn (((c!! c#f) c1) c5))
1
> (printb c#f)
#f
> (printb ((c& c#f) c#t))
#f
> (printb ((c& c#t) c#t))
#t
> (printb ((cv c#t) c#t))
#t
> (printb ((cv c#t) c#f))
#t
> (printb ((cv c#f) c#f))
#f
> (printb (c=0 c0))
#t
> (printb (c=0 c5))
application: not a procedure;
 expected a procedure that can be applied to arguments
  given: #t
  arguments...:
   #f
  context...:
   /usr/share/racket/collects/racket/private/misc.rkt:88:7
> (printb (c=0 c5))
#f
> (printb (c=0 c0))
#t
> (printb (c/2 c5))
#f
> (printb (c/2 c0))
#t
> (printb (c/2 (cn 1000)))
#t
> printpair: undefined;
 cannot reference undefined identifier
  context...:
   /usr/share/racket/collects/racket/private/misc.rkt:88:7
> printpair: undefined;
 cannot reference undefined identifier
  context...:
   /usr/share/racket/collects/racket/private/misc.rkt:88:7
> (printnpair (ccons (cn 10) (cn 20)))
ccons: undefined;
 cannot reference undefined identifier
  context...:
   /usr/share/racket/collects/racket/private/misc.rkt:88:7
> (printnpair (ccons (cn 10) (cn 20)))
ccons: arity mismatch;
 the expected number of arguments does not match the given number
  expected: 1
  given: 2
  arguments...:
   #<procedure:...box/numerals.scm:23:2>
   #<procedure:...box/numerals.scm:23:2>
  context...:
   /usr/share/racket/collects/racket/private/misc.rkt:88:7
> (printnpair ((ccons (cn 10)) (cn 20)))
(10 . 20)
>