On Wed, 14 Jun 2017, Gábor Csárdi wrote:
I don't think it is reasonable to change the parser this way. This is
currently valid R code:
a <- "foo"
"bar"
and with the new syntax, it is also valid, but with a different
meaning. Or you can even consider
a <- "foo"
bar %>% func() %>% print()
etc.
I like the idea of string literals, but the C/C++ way clearly does not
work. The Python/Julia way might, i.e.:
"""this is a
multi-line
lineral"""
This does look like a promising option; some more careful checking
would be needed to make sure there aren't cases where currently
working code would be broken.
Another Python idea worth considering is the raw string notation
r"xyx" that does not process escape sequences -- this would make
writing things like regular expressions easier.
Best,
luke
Gabor
On Wed, Jun 14, 2017 at 4:12 PM, William Dunlap via R-devel
<r-devel@r-project.org> wrote:
If you are changing the parser (which is a major change) you
might consider treating strings in the C/C++ way:
char *s = "A"
"B";
means the same as
char *s = "AB";
I am not a big fan of that syntax but it is widely used.
A backslash at the end of the line leads to errors when you accidently
put a space after the backslash and the editor doesn't flag it.
Bill Dunlap
TIBCO Software
wdunlap tibco.com
On Wed, Jun 14, 2017 at 3:58 AM, Andreas Kersting <r-de...@akersting.de>
wrote:
Hi,
I would really like to have a way to split long string literals across
multiple lines in R.
Currently, if a string literal spans multiple lines, there is no way to
inhibit the introduction of newline characters:
"aaa
+ bbb"
[1] "aaa\nbbb"
If a line ends with a backslash, it is just ignored:
"aaa\
+ bbb"
[1] "aaa\nbbb"
We could use this fact to implement string splitting in a fairly
backward-compatible way, since currently such trailing backslashes should
hardly be used as they do not have any effect. The attached patch makes the
parser ignore a newline character directly following a backslash:
"aaa\
+ bbb"
[1] "aaabbb"
I personally would also prefer if leading blanks (spaces and tabs) in the
second line are ignored to allow for proper indentation:
"aaa \
+ bbb"
[1] "aaa bbb"
"aaa\
+ \ bbb"
[1] "aaa bbb"
This is also implemented by this patch.
An alternative approach could be to have something like
("aaa "
"bbb")
or
("aaa ",
"bbb")
be interpreted as "aaa bbb".
I don't know the ins and outs of the parser of R (hence: please very
carefully review the attached patch), but I guess this would be more work
to implement!?
What do you think? Is there anybody else who is missing this feature in
the first place?
Regards,
Andreas
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--
Luke Tierney
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa Phone: 319-335-3386
Department of Statistics and Fax: 319-335-3017
Actuarial Science
241 Schaeffer Hall email: luke-tier...@uiowa.edu
Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu
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