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From: Jamison Hope <>
To: Kawa mailing list <>
Subject: Re: no class-of ?
Date: Fri, 22 Sep 2017 18:29:00 -0000	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On a somewhat related note, is there a way to define a macro that can
determine the type of an expression at macro expansion time, without
actually evaluating the expression?

I'd like to be able to do something along the lines of:

(define-syntax (ensure-boolean form)
  (syntax-case form ()
    ((_ expr)
     (let ((the-type (???? #'expr)))
       (cond ((eq? the-type boolean) #'expr)
             ((eq? the-type void)    #'(begin expr #t))
             ((eq? the-type int)     #'(= expr 0))
             (else (syntax-error "unsupported expression type")))))))

to be used as in:

(define (f x::double) ::boolean ...)
(define (g) ::int ...)
(define (h) ::void ...)

(list (ensure-boolean (let ((x 1.0)) (f x)))
      (ensure-boolean (g))
      (ensure-boolean (h)))


(list (let ((x 1.0)) (f x))
      (= (g) 0)
      (begin (h) #t))

> On Sep 21, 2017, at 11:23 AM, Per Bothner <> wrote:
> On 09/21/2017 04:11 AM, Sonny To wrote:
>> there seems to be class-of function to get the type of the r-value of a symbol.
> You can use the Java getClass method:
>  (VALUE:getClass)
> or:
>  (invoke VALUE 'getClass)
> or the "property" short-hand:
>  VALUE:class
>> I'm not familiar with with the standard libraries of scheme and i'm
>> googling to get documentation and find various scheme documentation
>> from mit-scheme/racket/guile but are not available in kawa.
>> Is there a place where I can find a list of functions built into kawa?
> The Kawa manual attempts to document all the Kawa functions.
> In the past I concentrated on documenting only Kawa extensions/differences
> from standard Scheme (so you needed to also have a copy of R5RS/R7RS), but
> I'm gradually making the Kawa manual more complete and self-contained.
> (There may still be some R7RS procedures missing, though.)
> There are also some implemented SRFIs, not all of which are fully documented
> in the Kawa manual.  See:
> Of course all of the Java APIs are always available, by using Java
> method calls:
> That is where you will find getClass documented:
> (the final '--' in the URL seems to be needed.)
> -- 
> 	--Per Bothner

Jamison Hope
The PTR Group

  reply	other threads:[~2017-09-22 18:29 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-09-21 11:11 Sonny To
2017-09-21 15:24 ` Per Bothner
2017-09-22 18:29   ` Jamison Hope [this message]
2017-09-22 19:23     ` Per Bothner
2017-09-22 22:18       ` Jamison Hope
2017-09-22 22:26         ` Per Bothner
2017-09-23 14:31           ` Jamison Hope
2017-09-24 21:52             ` Per Bothner
2017-09-25 16:58               ` Jamison Hope
2017-09-25 17:19                 ` Per Bothner

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