[plt-scheme] Dot-notation for structure field access

I haven't tested this, but you almost certainly need to add

(require-for-template mzscheme)

to the `dot' module.

Hope that helps,

sam th

On 3/11/07, jos koot <jos.koot at telefonica.net> wrote:
>
>
> Hi,
> Inspired by the dot notation of Jens Axel Søgaard I tried to eliminate the
> need for define-accessor. See enclosure. However, I can't get rid of the
> error reported at the end of my trial, reading:
> "compile: bad syntax; reference to top-level identifier is not allowed,
> because no #%top syntax transformer is bound in: acc85"
>
> Can anyone help me, please. Sorry that I don't send a stripped version of
> the problem. I have tried many stripped versions of my code, but in these
> the problem does not occur.
>
> Greetings, Jos Koot
>
> (((((lambda(x)((((((((x x)x)x)x)x)x)x)x))
>     (lambda(x)(lambda(y)(x(x y)))))
>    (lambda(x)(x)x))
>   (lambda()(printf "Greetings, Jos~n"))))
>
>
> ----- Original Message -----
> From: Jens Axel Søgaard
> To: George Herson
> Cc: plt-scheme at list.cs.brown.edu
> Sent: Thursday, March 08, 2007 11:13 PM
> Subject: [plt-scheme] Dot-notation for structure field access
>
> George Herson skrev:
>
> > May not be the best approach but I'm enjoying the
> > compactness of the resulting code (which allows
> > conventional table-name.column-name notation in a
> > sql-like mini-language).
>
> That remark sparked inspired me to play a little
> with #top in order to get the following to work:
>
> (require dot)
> (define-struct color (r g b) (make-inspector))
>
> (define-accessor r color-r)
> (define-accessor g color-g)
> (define-accessor b color-b)
>
> (define a (make-color 1 2 3))
> a.r  ; evaluates to 1
> a.g  ; evaluates to 2
> a.b  ; evaluates to 3
>
>
> The entire program, which by no means is well-tested, is below.
>
> /Jens Axel
>
> ; Put the entire program in a buffer, choose "Pretty Big"
> ; and click "Run".
>
> (module dot-helper mzscheme
>    (provide dot define-accessor)
>
>    (begin-for-syntax
>      (define accessors (list)))
>
>    (require-for-syntax (prefix srfi: (lib "1.ss" "srfi")))
>    (define-syntax (dot stx)
>      (syntax-case stx ()
>        [(dot expr accessor)
>         #`(#,(cdr (srfi:assoc #'accessor accessors module-identifier=?))
>              expr)]))
>
>    (define-syntax (define-accessor stx)
>      (syntax-case stx ()
>        [(define-accessor name getter)
>         (begin
>           (set! accessors (cons (cons #'name #'getter)
>                                 accessors))
>           #'(void))])))
>
> (module dot mzscheme
>    (provide (rename my-top #%top)
>             define-accessor
>             dot)
>
>    (require (lib "pregexp.ss")
>             dot-helper)
>
>    (define-for-syntax (contains-dot? sym)
>      (member #\. (string->list
>                   (symbol->string sym))))
>
>    (define-for-syntax (split-at-dot sym)
>      (cond
>        [(regexp-match #rx"^([^.]*)\\.([^.]*)$" (symbol->string sym))
>         =>(lambda (result)
>             (values (string->symbol (list-ref result 1))
>                     (string->symbol (list-ref result 2))))]
>        [else #f]))
>
>    (define-syntax (my-top stx)
>      (syntax-case stx ()
>        [(_ . name)
>         (and (identifier? #'name)
>              (contains-dot? (syntax-e #'name)))
>         (let-values ([(before after)
>                       (split-at-dot (syntax-e #'name))])
>           (with-syntax ([var (datum->syntax-object #'stx before)]
>                         [acc (datum->syntax-object #'stx after)])
>             #'(dot var acc)))]
>        [(_ . name)
>         #'(#%top . name)])))
>
>
>
> (require dot)
> (define-struct color (r g b) (make-inspector))
>
> (define-accessor r color-r)
> (define-accessor g color-g)
> (define-accessor b color-b)
>
> (define a (make-color 1 2 3))
> a.r
> a.g
> a.b
>
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>


-- 
sam th
samth at ccs.neu.edu