[plt-scheme] frtime

Hi,

Since picture->file uses imperative I/O, it's probably best to keep
this module in MzScheme and then lift / import the procedures you need
into the FrTime program.  For example,

(require (lifted "camera01.ss" make-camera picture->file))

in FrTime should allow you to define a camera with time-varying
properties, and the picture should change automatically when the
camera's properties change.

Let me know if you run into any problems.

Cheers,
Greg

On 1/16/08, geb a <geb_a at yahoo.com> wrote:
> Hello,
> I am trying to convert the following module to frtime
> but I've run into several difficulties mainly
> resolving the differences between mzscheme and frtime.
> I was trying to set up a pipe between the camera and
> output string but was unable to get it to compile.
>
> The purpose of the code is to provide an output string
> holding a current photograph at any given instant.
> Does it even make sense to use Frtime for this
> purpose?
>
> Thank you in advance for all of your help.  I really
> appreciate all of the past support.
>
> (module camera01  mzscheme
>
>   (require  (lib "url.ss" "net")
>             (lib "etc.ss")
>             (lib "process.ss"))
>
>   (define-struct camera (ip type direction mode
> resolution quality interval size preset language ))
>   ;a camera is a structure where ip..language are
> strings ; deleted for brevity...
>
>   ;camera->string: camera -> string
>   ;takes a camera and produces a string that
> represents the required state of the camera.
>   (define (camera->string a-camera)
>     (string-append "http://"
>                    (camera-ip a-camera)
>                    "/"
>                    (camera-type a-camera)
>                    "?Mode=" (camera-mode a-camera)
>                    "&Direction=" (camera-direction
> a-camera)
>                    "&Quality=" (camera-quality
> a-camera)
>                    "&Resolution=" (camera-resolution
> a-camera)
>                    "&Interval=" (camera-interval
> a-camera)
>                    "&Size=" (camera-size a-camera)
>                    "&PresetOperation=" (camera-preset
> a-camera)
>                    "&Language=" (camera-language
> a-camera)))
>
>
>   (define camera1 (make-camera "10.1.50.1"
> "SnapshotJPEG" "" "Refresh"  "640x480" "Clarity" "10"
> "STD" "Move" "0"))
>
>
>   (define (picture->file a-camera)
>     (local [(define in (get-pure-port
> (string->url(camera->string a-camera))))
>             (define (read-loop out input)
>               (let ([byte (read-byte input)])
>                 (cond
>                   [(eof-object? byte)
> (close-input-port input)]
>                   (else (begin
>                           (write-byte byte out)
>                           (read-loop out input))))))]
>
>       (let ((o (open-output-string)))
>         (begin
>           (read-loop o in )
>           o)))))
>
>   ;example usage
>   (picture->file camera1)
>
>
>
>
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