On Sun, 22 Jun 2014 11:58:59 -0400 Sam Tobin-Hochstadt <sa...@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 > <matth...@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" > >> <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 > >>>> > >>>> > >>>> > >>>> ____________________ Racket Users list: http://lists.racket-lang.org/users
