2013/5/31 Marc Feeley <feeley@iro.umontreal.ca>

On May 31, 2013, at 9:40 AM, Marc Feeley <feeley@IRO.UMontreal.CA> wrote:

>
> On May 31, 2013, at 9:28 AM, Nathan Sorenson <takeoutweight@hotmail.com> wrote:
>
>> When translating Clojure code to Scheme, I'm finding it quite easy to preserve source code information for the Gambit interpreter, so that when I get exceptions I am notified of the offending Clojure source lines. Is there an obvious way I could do this for compiled code as well?
>
> There isn't a form for this, but that would be useful and I have thought about adding it. Something like a "source-at" special form.
>
> For example,
>
> (source-at "foo.scm" 10 2 ;; file line column
> ((source-at "foo.scm" 10 8 cons)
> (source-at "foo.scm" 10 8 x)
> (source-at "foo.scm" 10 10 y)))
>
> would be equivalent to
>
> (cons x y)
>
> but with explicit source location information.
>
> Actually this source-at form can be easily defined as a macro give me a few minutes.

Here's the implementation of source-at.

Marc

;;; File: source-at.scm

(##define-syntax source-at
(lambda (form)

(define (unwrap x)
(if (##source? x) (##source-code x) x))

(apply (lambda (_ path line col expr)
(##make-source
(unwrap expr)
(##make-locat
(##path->container (unwrap path))
(##make-filepos (- (unwrap line) 1) (- (unwrap col) 1) 0))))
(unwrap form))))

;; test it:

(define (f x y)
(+ 1

(source-at "foo.scm" 10 2 ;; file line column

(/ x y))))

(pp (f 100 0))

;; Output:
;;
;; % gsi source-at.scm
;; *** ERROR IN f, "foo.scm"@10.2 -- Divide by zero
;; (/ 100 0)

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