Re: newline comparison?

[Chris Uzdavinis <chris@atdesk.com>]

Matthew Flatt <mflatt@cs.utah.edu> writes:

> >         ([string=? line "\n"]  (do-something)))
> 
> What would work in version 199.X (the upcoming release, available only
> through CVS), but not 103.X.

That's really an improvement!  Is 199.X stable?  Somewhat stable?  :)

> >         ([equal? (string-ref line 0) #\newline]
> >         ([eq? string-ref line 0) #\newline]  (do-something)))
> 
> Those should work.

I think that these failed because it was a \r\n combination, and the
read-line was leaving the #\return, which I mistook for a newline.  (I
was thinking this while driving home from work, but after I posted.)

> But I think the problem may be here:
> 
> >   (let ([line (read-line input)]) ;; assume this reads in a newline only
> 
> `read-line' strips off the newline character, so a line containing
> nothing will produce the empty string.

The 'any mode would fix then, and then I could compare for an empty
string, like this:

    (string=? "" line)

 
> Beware of variying newline conventions. For example, when reading a
> DOS/Windows file, you'll get both #\newline and #\return from the port
> (and `read-line' will return the #\return characters) unless it's opened
> in 'text mode.

Thanks.  :)  I'm guessing this was it.

-- 
Chris