[racket] Type of argument in a function

#lang racket

(define (plus x y)
  (unless (and (number? x) (number? y))
    (error 'plus (~a "expected two numbers, got: " x " " y)))
  (+ x y))

(plus 1 2)
(plus "x" 3)

2014-07-20 13:04 GMT+02:00 קוראל אלימלך <coral2301 at gmail.com>:
> How can i define that a function will get an integer argument?
>
> is its possible?
>
> for example:
> (define (func (x::Number))) /// its not working that way
>
> and if ill call the function with string there will be an error..
>
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-- 
--
Jens Axel Søgaard