Welcome to Racket v7.2.
> (hailstone-count 16)
5
> (hailstone-count 32)
6
> (hailstone-count 5)
6
> (hailstone-count 10)
7
> (hailstone-count 64)
7
> (hailstone-count 3)
8
> (hailstone-count 128)
8
> (hailstone-f 0)
empty
> (hailstone-f 1)
#<procedure>
> ((hailstone-f 1) 0)
1
> ((hailstone-f 1) 1)
1
> ((hailstone-f 1) 2)
; application: not a procedure;
;  expected a procedure that can be applied to arguments
;   given: empty
; [,bt for context]
> ((hailstone-f 3) 2)
2
> ((hailstone-f 3) 4)
3
> ((hailstone-f 3) 5)
; application: not a procedure;
;  expected a procedure that can be applied to arguments
;   given: empty
; [,bt for context]
> ((hailstone-f 6) 5)
6
> ((hailstone-f 6) 10)
; application: not a procedure;
;  expected a procedure that can be applied to arguments
;   given: empty
; [,bt for context]
> hailstone-inf
; terminate break [,bt for context]
  C-c C-c  C-c C-c  C-c C-c  C-c C-c  C-c C-c  C-c C-c  C-c C-c  C-c C-c  C-c C-c  C-c C-c  C-c C-c
Process scheme exited abnormally with code 1
> (repeat-inf hailstone-op)
#<procedure>
> hailstone-inf
#<procedure>
> (hailstone-inf 0)
1
> (hailstone-inf 1)
1
> (hailstone-inf 16)
5
> (hailstone-inf 128)
8
> (hailstone-inf 8934)
141
> (printn (cdiv2 c3))
1
> (printn (cdiv2 c5))
2
> (printn (cdiv2 (c 500)))
250
> (printn (cdiv2 (c 501)))
250
> gamma-h
#<procedure:gamma-h>
> (((c3 gamma-h) I) c1)
#<procedure>
> (printn (((c3 gamma-h) I) c1))
1
> (printn (((c3 gamma-h) I) c2))
; c2: undefined;
;  cannot reference an identifier before its definition
;   in module: top-level
; [,bt for context]
> (printn (((c3 gamma-h) I) (c 2)))
2
> (printn (((c3 gamma-h) I) (c 4)))
3
> (printn (((c3 gamma-h) I) (c 8)))
4
> (printn (((c3 gamma-h) I) (c 16)))
5
> (printn (((c3 gamma-h) I) (c 32)))
7
> (printn (((c3 gamma-h) I) (c 64)))
11
> (printn (((c3 gamma-h) (K c0)) (c 64)))
3
> (printn (((c3 gamma-h) (K c0)) (c 32)))
3
> (printn (((c3 gamma-h) (K c0)) (c 16)))
3
> (printn (((c3 gamma-h) (K c0)) (c 8)))
3
> (Y gamma-h)
; terminate break [,bt for context]
  C-c C-c
Process scheme exited abnormally with code 1
> ; /: contract violation
;   expected: number?
;   given: "error"
;   argument position: 2nd
; [,bt for context]
> #<procedure>
> ef
#<procedure:ef>
> (ef 2)
; /: contract violation
;   expected: number?
;   given: "error"
;   argument position: 2nd
; [,bt for context]
> (ef 3)
; /: contract violation
;   expected: number?
;   given: "error"
;   argument position: 2nd
; [,bt for context]
> Z
#<procedure:Z>
> (Z gamma-h)
; gamma-h: undefined;
;  cannot reference an identifier before its definition
;   in module: top-level
; [,bt for context]
> (Z gamma-h)
#<procedure>
> ((Z gamma-h) c0)
; terminate break [,bt for context]
  C-c C-c
Process scheme exited abnormally with code 1
Welcome to Racket v7.2.
> (my-if (> 2 0) 5 (/ 3 "error"))
; /: contract violation
;   expected: number?
;   given: "error"
;   argument position: 2nd
; [,bt for context]
> (if (> 2 0) 5 (/ 3 "error"))
5
>  ((Z gamma-h) c0)
; Z: undefined;
;  cannot reference an identifier before its definition
;   in module: top-level
; [,bt for context]
>  ((Z gamma-h) c0)
#<procedure>
> (printn ((Z gamma-h) c0))
1
> (printn ((Z gamma-h) c1))
1
> (printn ((Z gamma-h) c3))
8
> (printn ((Z gamma-h) (c 128)))
8
> (printn ((Z gamma-h) (c 64)))
7
> (printn ((Z gamma-h) (c 5)))
6
>