[racket] Typed racket and command line parameters

On Sun, 22 Jun 2014 11:58:59 -0400
Sam Tobin-Hochstadt <samth at cs.indiana.edu>
wrote:

> Fortunately, one of those casts can be eliminated with a bit of type
> annotation on `NUM`.   Full code here:
> https://gist.github.com/samth/48bf2ccb2c510c75017e
> 
> (define parms
>   (command-line
>    #:program "mypgm"
>    #:once-each
>    [("-v" "--verbose") "Show verbose output" (opt-verbose-mode #t)]
>    [("-m" "--max-size")
>     #{NUM : String} ("Max size." "NUM")
>     (opt-max-size (cast (string->number NUM) Real))]))
> 
> Sam
> 

This is indeed nice. Thanks for the variation to Matthias solution.

-- 
Manfred

> 
> On Sun, Jun 22, 2014 at 11:25 AM, Matthias Felleisen
> <matthias at ccs.neu.edu> wrote:
> >
> > I would use Real for the parameter type and then cast twice:
> >
> > (define parms
> >   (command-line
> >    #:program "mypgm"
> >    #:once-each
> >    [("-v" "--verbose") "Show verbose output" (opt-verbose-mode #t)]
> >    [("-m" "--max-size")
> >     NUM
> >     ("Max size." "NUM")
> >     (opt-max-size (cast (string->number (cast NUM String)) Real))]))
> >
> > The casts bring out that you are willing to sacrifice precision of
> > error messages for concision in code.
> >
> > -- Matthias
> >
> >
> >
> >
> > On Jun 22, 2014, at 12:06 AM, Manfred Lotz wrote:
> >
> >> On Sat, 21 Jun 2014 10:12:27 -0400
> >> "Alexander D. Knauth"
> >> <alexander at knauth.org> wrote:
> >>
> >>> The first thing I notice is that opt-max-size is a (Parameterof
> >>> Any), but you use string->number on it. So you should probably
> >>> put a guard on the opt-max-size parameter something like this: (:
> >>> opt-max-size (Parameterof Any Real)) (: opt-max-size-guard (Any
> >>> -> Real)) (define (opt-max-size-guard val)
> >>>  (cond [(real? val) val]
> >>>        [(string? val) (opt-max-size-guard (string->number val))]
> >>>        [else (error "Max size: must be a real number")]))
> >>>
> >>> (define opt-max-size (make-parameter 0 opt-max-size-guard))
> >>>
> >>
> >> Thanks for this, which works fine. I'm not qite sure I like this
> >> as it seems to make the code more complicated. But if this is the
> >> only possibility what can be done.
> >>
> >>
> >>
> >>> On Jun 21, 2014, at 3:45 AM, Manfred Lotz
> >>> <manfred.lotz at arcor.de> wrote:
> >>>
> >>>> Hi there,
> >>>> I try to change one of my programs to typed racket and fail
> >>>> because of errors when dealing with command line arguments.
> >>>>
> >>>> Here a minimum example:
> >>>>
> >>>> #lang typed/racket/base
> >>>>
> >>>> (require racket/cmdline)
> >>>>
> >>>>
> >>>> (: opt-verbose-mode (Parameterof Boolean))
> >>>> (define opt-verbose-mode (make-parameter #f))
> >>>> (: opt-max-size (Parameterof Any))
> >>>> (define opt-max-size (make-parameter "0"))
> >>>>
> >>>>
> >>>>
> >>>> (define parms
> >>>> (command-line
> >>>>  #:program "mypgm"
> >>>>  #:once-each
> >>>>  [("-v" "--verbose") "Show verbose output" (opt-verbose-mode #t)]
> >>>>  [("-m" "--max-size") NUM ("Max size." "NUM") (opt-max-size NUM)
> >>>> ] ))
> >>>>
> >>>>
> >>>> (define (myfun)
> >>>> (when (opt-verbose-mode)
> >>>>   (if (> (string->number (opt-max-size)) 0)
> >>>>       #t
> >>>>       #f)))
> >>>>
> >>>>
> >>>> What do I do wrong? Any hint appreciated.
> >>>>
> >>>> --
> >>>> Thanks,
> >>>> Manfred
> >>>>
> >>>>
> >>>>
> >>>>