# [racket-dev] (round), etc. in Typed Racket

At Sat, 11 Dec 2010 18:35:17 -0700,
Petey Aldous wrote:
>* I've discovered what may be a bug in the type system of Typed Racket. The
*>* functions that round - (round), (truncate), (ceiling), etc. are typed as
*>* Real, not Integer; however, the result of (integer? (round (* 10e15
*>* (random)))) is consistently true - and the same holds for the other rounding
*>* functions.
*
Typed Racket's Integer type corresponds to racket's exact integers
(exact-integer?, not integer?).
integer? can return true for floating point numbers:
(integer? 1.0) -> #t
but exact-integer? cannot.
The types for round, truncate, etc. take this into account. For
instance, if you round an exact rational, the type of the result will
be Integer, whereas if you round a floating point number, you get a
Float back.
>* Is this intentional? If so, why? If it is (or even if it isn't), how can I
*>* transform the result of (random) to an Integer?
*
You can use inexact->exact on the result of round.
Vincent