Yep, that works, thank you.
I did not know that EOF alone could be there.
On Monday, April 23, 2018 at 2:16:52 AM UTC+2, Sam Tobin-Hochstadt wrote:
>
> Typed Racket is reminding you that `read-line` can produce EOF. If you
> handle that (for example, with `(assert something string?)`) then it
> works correctly.
>
> Sam
>
> On Sun, Apr 22, 2018 at 4:40 PM, Zelphir Kaltstahl
> <zelphirk...@gmail.com <javascript:>> wrote:
> > Ah OK, I understand that additional newline. Since the code matching the
> > regex is run before that newline gets in, the newline will be on the
> > input port.
> >
> > In DrRacket I observe the following:
> >
> > (I remembered that there are negative numbers :D and my regex got a bit
> > more complicated.)
> >
> > ~~~
> > (regexp-try-match #rx"\\s*^(-?[1-9]+[0-9]*)$|\\s*^0$"
> (current-input-port))
> > ~~~
> >
> > When I run it the first time, I get the "input box" where I can click
> > the "EOF" button on the right and the regex seems to work. When I try
> > again immediately after, the first time, there is still an #<eof> on the
> > port, which apparently was not consumed, so it will immediately return
> > #f. I can get rid of that #<eof> by running (read-line) once. On REPL
> > line I would have a newline and in DrRacket I have an #<eof>.
> >
> > On REPL it does not stop expecting input, because it never receives an
> > #<eof>. I read somewhere on Stackoverflow that I input #<eof> by
> > pressing Ctrl+d and that may be true, but it does not work in REPL,
> > because that shuts down the REPL. So basically it seems impossible to
> > test such regular expressions on REPL.
> >
> > I think I will instead use:
> >
> > ~~~
> > (let ([something (read-line (current-input-port) 'any)])
> > (... do regex things on finished string here ...))
> > ~~~
> >
> > to work around this problem in the future. This will actually finish the
> > line at any marker of a new line and then let me work with the regex
> > more comfortably. Also instead of running it in the REPL, I will
> > probably run a small program instead with racket <racket file>.
> >
> > Thanks for clearing up my confusion!
> >
> > I tried to write this in Typed Racket and the following is what I got.
> > This works:
> >
> > ~~~
> > (: get-input-number (-> Integer))
> > (define (get-input-number)
> > (let loop : Integer ()
> > (let ([something (read-line (current-input-port) 'any)])
> > (cond [(string? something)
> > (let ([number-representation (string->number something)])
> > (cond [(exact-integer? number-representation)
> number-representation]
> > [else (printf "nope~n")
> > (loop)]))]
> > [else (printf "nope~n")
> > (loop)]))))
> >
> > (get-input-number)
> > ~~~
> >
> > While the following does not work:
> >
> > ~~~
> > (define (get-input-number-2)
> > (let loop : Integer ()
> > (let* ([something (read-line (current-input-port) 'any)]
> > [match-res (regexp-match #rx"(^-?[1-9]+[0-9]*$)|(^0$)"
> something)])
> > (cond [(string? something)
> > (let ([number-representation (string->number something)])
> > (cond [(exact-integer? number-representation)
> number-representation]
> > [else (printf "nope~n")
> > (loop)]))]
> > [else (printf "nope~n")
> > (loop)]))))
> >
> > (get-input-number-2)
> > ~~~
> >
> > The opening paren of regexp-match is underlined and when I run this code
> > I get the lengthy error message:
> >
> > ~~~
> > main.rkt:34:22: Type Checker: No function domains matched in function
> > application:
> > Domains: (U Byte-Regexp Bytes Regexp String) (U Bytes Input-Port)
> > Integer (U False Integer) (U False Output-Port) Bytes #f *
> > (U Byte-Regexp Bytes Regexp String) (U Bytes Input-Port)
> > Integer (U False Integer) (U False Output-Port) #f *
> > (U Byte-Regexp Bytes Regexp String) (U Bytes Input-Port)
> > Integer (U False Integer) #f *
> > (U Byte-Regexp Bytes Regexp String) (U Bytes Input-Port)
> > Integer #f *
> > (U Byte-Regexp Bytes Regexp String) (U Bytes Input-Port) #f *
> > (U Byte-Regexp Bytes) (U Bytes Input-Port Path-String) Integer
> > (U False Integer) (U False Output-Port) Bytes #f *
> > (U Byte-Regexp Bytes) (U Bytes Input-Port Path-String) Integer
> > (U False Integer) (U False Output-Port) #f *
> > (U Byte-Regexp Bytes) (U Bytes Input-Port Path-String) Integer
> > (U False Integer) #f *
> > (U Byte-Regexp Bytes) (U Bytes Input-Port Path-String) Integer
> #f *
> > (U Byte-Regexp Bytes) (U Bytes Input-Port Path-String) #f *
> > (U Regexp String) Path-String Integer (U False Integer) (U
> > False Output-Port) Bytes #f *
> > (U Regexp String) Path-String Integer (U False Integer)
> > context...:
> >
> >
> /usr/share/racket/pkgs/typed-racket-lib/typed-racket/typecheck/tc-toplevel.rkt:345:0:
>
>
> > type-check
> >
> >
> /usr/share/racket/pkgs/typed-racket-lib/typed-racket/typecheck/tc-toplevel.rkt:588:0:
>
>
> > tc-module
> >
> > /usr/share/racket/pkgs/typed-racket-lib/typed-racket/tc-setup.rkt:94:0:
> > tc-module/full
> >
> >
> /usr/share/racket/pkgs/typed-racket-lib/typed-racket/typed-racket.rkt:23:4
> > standard-module-name-resolver
> > ~~~
> >
> > (Racket 6.10.1)
> >
> > I am aware, that I do not really need the match-res, but this is only
> > some trying out of stuff. I am not really sure what it expects me to do
> > about the regexp-match. It seems it must be used differently in TR.
> > Should I put this in a new question ("How to use regexp-match in TR?")
> > instead?
> >
> >
> > On 22.04.2018 15:15, Matthew Flatt wrote:
> >> At Sun, 22 Apr 2018 14:54:26 +0200, Zelphir Kaltstahl wrote:
> >>> I am sorry, I think I am still misunderstanding it.
> >>>
> >>> When I try:
> >>>
> >>> (regexp-try-match #rx"^[1-9]+[0-9]*$" (current-input-port))
> >>>
> >>> It also results immediately in:
> >>>
> >>> #f
> >> Using stdin both for reading an expresion and getting input can be
> >> confusing. At Racket's ">" prompt, when you run
> >>
> >> > (regexp-try-match #rx"^[1-9]+[0-9]*$" (current-input-port))
> >>
> >> by hitting Return, then a newline is included is in the input stream
> >> just after the `(regexp-try-match ...)` expression. That newline is
> >> still there when you try to match against the regexp, so the match
> >> fails.
> >>
> >> DrRacket separates the input stream for expressions and for
> >> `current-input-port`. So, if you try that expression in DrRacket's
> >> interactions area, and if you hit the "EOF" button (to the right of the
> >> input box) instead of Return after a number, then you should get a
> >> match. Note that if you hit Return after the number, then it won't
> >> match even in DrRacket, because the input port will have a newline
> >> after the number.
> >>
> >
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