[racket] Arity check

From: Matthew Flatt (mflatt at cs.utah.edu)
Date: Wed Aug 21 09:02:11 EDT 2013

Although Racket is dynamically typed, the compiler does notice an
obvious arity mismatch, and it logs a warning.

Some ways to see warnings:

 * In DrRacket, choose "Show Log" from the "View" menu, and set the
   filter to "warning" (which shows all warnings) or
   "warning at optimizer" (which shows only warnings from the optimizer).

 * Start Racket from the command line with

      racket -W warning


      racket -W "error warning at optimizer"

   to direct warnings to stderr.

   (You probably don't want just `-W warning at optimizer', because that
    would hide logged errors, in case there are any.)

 * In Racket using XREPL,

       ,log warning

   shows warnings.

At Wed, 21 Aug 2013 12:16:52 +0400, Roman Klochkov wrote:
> Why racket doesn't check arity when compiling?
> (define (test)
>   (car 12 3))
> compiles and even runs. Ir raises an error only when test is called.
> I can have desirable result making
> (define-syntax car*
>   (make-set!-transformer
>    (λ (stx)
>      (syntax-case stx ()
>        [(car* x) (syntax-protect (syntax/loc stx (car x)))]
>        [(car* x ...) (raise-argument-error 'car "one argument" (syntax->datum 
> #'(x ...)))]
>        [car* (syntax-protect (syntax/loc stx car))]))))
> (define (test)
>   (car* 12 3))
> But it is cumbersome (I'll have to wrap every function) and I don't understand 
> why compiler shouldn't see function contracts.
> -- 
> Roman Klochkov____________________
>   Racket Users list:
>   http://lists.racket-lang.org/users

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