[racket] Typed racket and command line parameters

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
> > 
> > 
> > 
> > 
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