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

This seems like an unfortunate naming discrepancy.
Robby
On Sat, Dec 11, 2010 at 7:52 PM, Vincent St-Amour <stamourv at ccs.neu.edu> wrote:
>* 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
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