[Rd] Multi-line string constants: proposed patch

[Peter Dalgaard]

Kevin Wright <kwright at 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.
>   
> In the files src/main/gram.y and src/main/gram.c strings
> are parsed with the StringValue function.  Looking at the function it is
> clear that a newline character (not the two-byte '\n') generates an error:
> 
> static int StringValue(int c)
> {
> ...
> 	if (c == '\n') {
> 	    xxungetc(c);
> 	    return ERROR;
> 	}
> 
> ...
> }

...
> 
> C:\R\R-devel\src\main>diff ogram.c gram.c
> 3122,3125c3122,3125
> <       if (c == '\n') {
> <           xxungetc(c);
> <           return ERROR;
> <       }
> ---
> //    if (c == '\n') {
> //        xxungetc(c);
> //        return ERROR;
> //    }
> 
> Presumably the same change should be made in gram.y
> 
> 
> Thanks for considering this patch.

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.

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
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