Welcome to Racket v7.2.
> (fact 10)
3628800
> (fact-c (lambda (x) x) 10)
3628800
> (fact-c (lambda (x) (+ x 2)) 10)
3628802
> (f (lambda (x) x))
6
> (call-cc f)
; call-cc: undefined;
;  cannot reference an identifier before its definition
;   in module: top-level
; [,bt for context]
> (call/cc f)
2
>