1.5 years ago, I struggled with the command-line, finally I thought
`parse-command-line` is friendlier than its macro form `command-line`, and
got the solution with `cast`:
;;; firstly, define your precise Help-Table.
(Listof (U (Pairof 'usage-help String)
(Pairof 'once-each (Listof (List (Listof String)
String String Void)
((cast parse-command-line (-> String (Vectorof String) Help-Table (-> Any
Void) (Listof String) (-> String Void) Void))
(format "~a ~a" (#%module) (path-replace-suffix (cast
(file-name-from-path (#%file)) Path) #""))
`([usage-help . ,(format "~a~n" desc)]
[once-each [("-p") ,(λ [[_ : String] [port : String]] (sakuyamon-port
(cast (string->number port) (Option Index))))
("Use an alternative <port>." "port")]
[("-w") ,(λ [[_ : String] [mw : String]]
(sakuyamon-max-waiting (cast (string->number mw) Positive-Index)))
("Maximum number of clients can be waiting for
[("-t") ,(λ [[_ : String] [ict : String]]
(sakuyamon-connection-timeout (cast (string->number ict) Positive-Index)))
("Initial connection timeout." "ict")]
[("--SSL") ,(λ [[_ : String]] (sakuyamon-ssl? #true))
("Enable SSL with 443 as default port.")]])
(λ [!] (serve-forever))
(lambda [[-h : String]]
(display (string-replace -h #px" -- : .+?-h --'\\s*" ""))
at that time, I was a freshman to typed racket, hence so many `cast` in the
solution. The `cast` form is inefficient, but in that situation it's
The other reason was, the annotation of `parse-command-line` lacks the 6th
optional argument which I always need to filter the help message.
Yes, it's ugly, but better than losing the type information of important
Engineering is the art of tradeoffs.
On Mon, Mar 6, 2017 at 3:08 PM, kay <klu...@gmail.com> wrote:
> For a complex syntax form like `command-line`, I have difficulty correctly
> annotate the bindings it defines.
> More specifically, in the below code, for variable `msg`, even the
> document says the `#:args` binds as list of **strings**, but the error
> indicates that it somehow is declared as `Listof Any`.
> Similarly, for variable `ch` bound in line 11, I believe it should always
> be `String`, but it somehow is declared to be `Any`.
> What should I do with this type of error, if I want my varaibles to be
> more precisely typed than just `Any`?
> : https://docs.racket-lang.org/reference/Command-Line_
> 1 #lang typed/racket
> 3 (define *channel* (make-parameter "#general"))
> 4 (define *message* : (Parameterof (Listof String)) (make-parameter
> 7 (define (parse-cmdline)
> 8 (command-line
> 9 #:program "q"
> 10 #:once-each
> 11 [("-c" "--channel") ch "slack channel to post (default: use
> .qrc setting or default)" (*channel* ch)]
> 12 #:args msg
> 13 (*message* msg)))
> 16 #|
> 17 tr.rkt:11:91: Type Checker: Wrong argument to parameter - expected
> String and got Any in: (*channel* ch)
> 18 tr.rkt:13:5: Type Checker: Wrong argument to parameter - expected
> (Listof String) and got (Listof Any) in: (*message* msg)
> 19 |#
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