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"
> <alexan...@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.l...@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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>>> http://lists.racket-lang.org/users
>>
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>
>
>
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