R devel - Sep 2004 - FW: Parsing multi-line strings. Bug? Feature?

>  Kevin Wright <kwright@eskimo.com> writes:
>
>  > R 1.9.1 requires multi-line strings to contain a backslash at the
>  > end of each line (except the last line).  As noted by Mark
>  > Bravington (http://tolstoy.newcastle.edu.au/R/help/02b/5199.html)
>  > this requirement appears to be undocumented.
>  > 
>  > In S-Plus 6.2, multi-line strings do not need a backslash for
continuation.
>  > 
>  > I recently (http://tolstoy.newcastle.edu.au/R/devel/04b/0256.html)
>  > requested compatability with S-Plus and was told to contribute
>  > a patch and then it would be considered.  Here is the proposed patch.
<<snip>>
>  > Thanks for considering this patch.
>
> Peter Dalgaard wrote:
>  Sorry, I don't think that is good enough (notwithstanding the
>  nonstandard comment character). Notice that Splus does this:
>
>  > x <- "foo
>  Continue string: bar
>  Continue string: baz"
>
>  (and the entry is interruptible with Ctrl-C too)
>
>  There's a very good reason for the change of prompt, as anyone who has
>  debugged SAS code with stray quotes will tell you: The system would
>  appear to be completely unresponsive because all input is being eaten
>  by the string readers.
I think the following patch in StringValue might address Peter Dalgaard's
point: when a bare newline is found (i.e. not preceded by a backslash), it's
pushed back onto the character stack via xxungetc(c) and StringValue pretends
that it's just read a backslash instead. Then, as usual, it looks for the
next character which is of course a newline, and proceeds as normal.

Output is from diff gram.c on R-devel from 7/9/2004. I hope the comments look
sufficiently standard now (I'm not a C programmer).

Mark

3122a3123,3124
>           /* Old behaviour was: return ERROR; */
>           /* Now pretend there was a backslash before EOL */
3124c3126
<           return ERROR;
---
>           c = '\\';

>
*******************************

Mark Bravington
CSIRO (CMIS)
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phone (61) 3 6232 5118
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Mark.Bravington@csiro.au