Problem with ghc on Windows ME

[Simon Peyton-Jones]

Well found!  Still, I found I could not understand the rules.

But I think the story this
	Convert	\"	to	\\\"
otherwise convert	"	to 	\"
otherwise do no conversion

I think it's probably easiest to express this directly:

translate :: String -> String
translate str = '"' : go str
  where go ('\\' : '"' : s) = '\\' : '\\' : '\\' : '"' : go s
	 go ('"' : s) = '\\' : '"' : go s
	 go (c:s) = c : go s
 	 go [] = ['"']

Simon

| -----Original Message-----
| From: Simon Marlow
| Sent: 29 January 2004 14:53
| To: Claus Reinke; Simon Peyton-Jones;
glasgow-haskell-users at haskell.org
| Subject: RE: Problem with ghc on Windows ME
| 
| After Googling around a bit, I found this description of exactly how
Windows interprets command lines
| in the C runtime:
| 
|
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccelng
/htm/progs_12.asp
| 
| As you can see, the rules are indeed very strange, but they are
invertible.  I think this code should do
| the trick:
| 
| translate :: String -> String
| translate str = '"' : snd (foldr escape (True,"\"") str)
|   where escape '"'  (_,     str) = (True,  '\\' : '"'  : str)
|         escape '\\' (True,  str) = (True,  '\\' : '\\' : str)
|         escape '\\' (False, str) = (False, '\\' : str)
|         escape c    (_,     str) = (False, c : str)
| 
| Cheers,
| 	Simon
| 
| > -----Original Message-----
| > From: glasgow-haskell-users-bounces at haskell.org
| > [mailto:glasgow-haskell-users-bounces at haskell.org] On Behalf
| > Of Simon Marlow
| > Sent: 29 January 2004 11:31
| > To: Claus Reinke; Simon Peyton-Jones;
| > glasgow-haskell-users at haskell.org
| > Subject: RE: Problem with ghc on Windows ME
| >
| >
| > > So does that mean functionality has been lost in the move from
| > > ghc-6.0.1?
| >
| > No, the behaviour is improved in 6.2 because we're now
| > careful to escape
| > quotes before passing the command-line to the operating system.
| >
| > I think confusion has arisen because Simon pointed out that there's
no
| > way, on Windows, to pass this sequence of characters as an
| > argument to a
| > command:
| >
| >    \"
| >
| > This is not entirely true, I just discovered that the
| > sequence \\\" will
| > turn into \".  But in general, the sequence \\ does not turn into \.
| > Windows' command-line quoting rules are highly mysterious, to say
the
| > least.
| >
| > So the patch I posted is not complete.  It looks like rawSystem
should
| > additionally translate \" as \\\".
| >
| > > Because that (on win98) happily accepts such useful
| > > contraptions as
| > >
| > >     System.Cmd.rawSystem "\"c:\\silly
| > > space\\Vim\\vim62\\gvim.exe\" --servername GVIM --remote-send
| > > \":echo \\\"hi \\\\\\\" there\\\"<cr>\"" >>= print
| >
| > The idea is that you should pass to rawSystem *exactly* the
| > command and
| > arguments you want to run, with no quoting except that required by
the
| > Haskell lexical syntax.  You'll notice that rawSystem now takes the
| > command and list of arguments separately in 6.2.  The
| > implementation of
| > rawSystem will attempt to compensate for the internal translation
that
| > Windows does on the command-line; on Unix no translation is
necessary.
| > So clients of rawSystem should be more portable, because they
| > don't have
| > to know about quoting that happens under the hood.
| >
| > Your example will probably work once it's reformulated for
| > 6.2's version
| > of rawSystem, and once we fix rawSystem in light of the \\\" hack I
| > discovered above.
| >
| > Cheers,
| > 	Simon
| > _______________________________________________
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| > Glasgow-haskell-users at haskell.org
| > http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
| >