[plt-scheme] Help on newline when writing to a file

At Wed, 9 Jan 2008 13:23:10 +0000, Dave Gurnell wrote:
> Noel wrote:
> > Try this:
> >
> > (display "\r\n")
> 
> 
> So on Windows, (printf "~n") and (printf "\r\n") aren't equivalent?  

No. `(printf "~n")', `(printf "\n")', and `(newline)' are all
equivalent.

If you're printing to a file port that was opened in 'text mode, then
all of those things produce #"\r\n". In 'binary mode (the default),
they produce #"\n".

> The documentation seems to suggest this:
> 
>    -- SNIP --
> 
>    -  ~n or ~% prints a newline
> 
>    -- SNIP --

I'll clarify in the docs that it means `#\newline'.

> why have ~n at all?

It pre-dates "\n" support in string literals. I never use it anymore.

> The documentation for ~w  
> below reads:
> 
>    -- SNIP --
> 
>    -  ~w, where w is a whitespace character, skips characters in  
> format-string
>      until a non-whitespace character is encountered or until a second  
> end-of-line
>      is encountered (whichever happens first). An end-of-line is  
> either #\return,
>      #\newline, or #\return followed immediately by #\newline (on all  
> platforms).
> 
>    -- SNIP --
> 
> which implies that ~w is platform aware.

No, it means that "~w" recognizes all of the usual conventions
independent of what platform you're using.

> Is there call for a platform  
> specific line break escape here?

I think that's best left to the port mode.

Matthew